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gabions unchanged. Results from the experiment are provided below in Table 6 and Figure 12. Effect of Gabion Fill-16 mm Thickness The final gabions to be tested were a thickness of 16 mm, with the contents of the gabions unchanged. Results from the experiment are provided below in Table 6 and Figure 12. Table 6. Results of 16 mm thickness gabion models in reducing total scour depth. Effect of Gabion Fill-50 mm Sediment Depth The cumulative scour at various time intervals were recorded for each model of each fill type. This is represented in graphical form for when sediment depth varied from 40 mm and 50 mm. At certain time intervals, the height of the vertical sluice gate downstream of the bridge pier was lowered in order to increase the flow depth and simulate river flooding, as shown in Table 2. The results from all thicknesses of gabion, as shown in Figure 13, generally show that the fill of the gabion models is largely irrelevant in the reduction of scour when the sediment depth of the sand sediment was 50 mm. This is evident when the thickness of the gabion models was 8 mm (C8, S8, P8), which resulted in the three different materials all following the same trendline as when the experiment was performed with no scour countermeasure surrounding the bridge pier. When the gabion models were at a thickness of 16 mm, the trendline of the graph (C12, S12, P12) again closely resembles that of the no gabion experiment, except for P16, which appears

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to be an anomalous result, considering the drastic reduction of the scour depth (4 mm less than C16), when compared to P16 and S16. Furthermore, if plastic was the most effective material in the gabions at Effect of Gabion Fill-50 mm Sediment Depth The cumulative scour at various time intervals were recorded for each model of each fill type. This is represented in graphical form for when sediment depth varied from 40 mm and 50 mm. At certain time intervals, the height of the vertical sluice gate downstream of the bridge pier was lowered in order to increase the flow depth and simulate river flooding, as shown in Table 2. The results from all thicknesses of gabion, as shown in Figure 13, generally show that the fill of the gabion models is largely irrelevant in the reduction of scour when the sediment depth of the sand sediment was 50 mm. This is evident when the thickness of the gabion models was 8 mm (C8, S8, P8), Eng 2020, 1 200 which resulted in the three different materials all following the same trendline as when the experiment was performed with no scour countermeasure surrounding the bridge pier. Eng 2020, 1, FOR PEER REVIEW 13 Figure 13. Graph representing all thicknesses of gabion models and the cumulative scour depth at a sediment depth of 50 mm. At 8 mm thickness, the gabions were not successful at reducing bridge pier scour, as both P8 and C8 contributed to no reduction in the scour depth, and the effectiveness of the

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gabion models was not advantageous. In two out of three cases, no scour reduction was observed when compared with the original experiment when conducted with no scour countermeasures enabled. At 12 mm thickness, the gabion models led to a reduced total scour depth. The results were, however, not as effective as when the gabions were at a 40 mm sediment depth, as the percentage reduction in scour was less than 20% for all cases of varied fill types when compared to results higher than 34.8%. Increasing the thickness of the gabion models from 8 to 12 mm led to a reduction in scour; for example, increasing the thickness of the stone gabion model from 8 to 12 mm led to a further 26.1% reduction in the total scour depth. At 16 mm thickness, the total scour depth was similar to the results gathered from when no scour countermeasure was installed, excluding P16, which remained the same total scour depth as P12 (a decrease of 15.4%) and C16 which decreased by 3.8%. When the gabion models were at a thickness of 16 mm, the trendline of the graph (C12, S12, P12) again closely resembles that of the no gabion experiment, except for P16, which appears to be an anomalous result, considering the drastic reduction of the scour depth (4 mm less than C16), when compared to P16 and S16. Furthermore, if plastic was the most effective material in the gabions at reducing scour, then this result would be expected to be replicated at gabion thicknesses 8 mm

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and 12 mm. Whilst P12 does produce the lowest total scour depth in the materials tested, it is only by 1 mm, which is a fine margin and therefore inconclusive. The results of C12, P12 and S12 follow the same trendline as when the no gabion model test was conducted, however, there was a much more significant reduction in the total scour depth when compared to the 8 mm thickness gabion models. At 8 mm thickness, the gabions were not successful at reducing bridge pier scour, as both P8 and C8 contributed to no reduction in the scour depth, and the effectiveness of the gabion models was not advantageous. In two out of three cases, no scour reduction was observed when compared with the original experiment when conducted with no scour countermeasures enabled. At 12 mm thickness, the gabion models led to a reduced total scour depth. The results were, however, not as effective as when the gabions were at a 40 mm sediment depth, as the percentage reduction in scour was less than 20% for all cases of varied fill types when compared to results higher than 34.8%. Increasing the thickness of the gabion models from 8 to 12 mm led to a reduction in scour; for example, increasing the thickness of the stone gabion model from 8 to 12 mm led to a further 26.1% reduction in the total scour depth. At 16 mm thickness, the total scour depth was similar to the results gathered from when no scour countermeasure was installed, excluding P16,

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which remained the same total scour depth as P12 (a decrease of 15.4%) and C16 which decreased by 3.8%. The increase in thickness of the gabion models were also not as effective at reducing bridge pier scour; this can be seen in the similarities between S16 and S8, and C16 and C12. Both gabion models increased in thickness, which would indicate a better capacity to prevent scour; however, in the case of S16, the total scour increased by 1 mm to 26 mm, and C16 obtained the same total scour depth of 25 mm. The exception to this, once the anomaly P16 is excluded, is the 12 mm thick gabion models, all of which performed better than their respective material types in the 8 mm and 16 mm thick gabion models. Time also impacts the cumulative scour depth, as in all but four cases (P16, S12, P12 and no gabion), and the majority of scour accumulated in the first 30 s of the experiment. In each model tested, there was no additional deposition of sand sediment into the developing scour hole, as can be seen from Figure 13; all models led to an increase, or maintenance of scour depth. Overall, the type of gabion fill used at a sediment depth of 50 mm sand sediment was largely irrelevant in the reduction of the total scour depth surrounding bridge piers. All types of fill and thicknesses performed relatively poorly in the reduction of total scour depth, with the highest reduction of scour 19.2%, being obtained when using

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plastic material at thicknesses 12 and 16 mm. Although plastic material does appear the most effective material at reducing scour, the result of P16 must be disregarded, as its results differ drastically from that of C16 and S16 and the results are inconclusive. Effect of Gabion Fill-40 mm Sediment Depth The placement depth of the gabions was decreased by 10 mm and set to 40 mm sediment depth. Figure 14 summarises all results at a 40 mm sediment depth. The results of all gabion thicknesses and their various fills, as shown in Figure 14, show that at a sediment depth of 40 mm, the effect of gabion fills and their thicknesses are much more effective than when the same models were installed beneath a level of 50 mm. The most effective fill type of the gabions in reducing local scour was the stone and plastic filled gabions, both of which have an average scour depth of 15 mm, which meant an average reduction of 28.57% when comparing to the original experiment undertaken with no scour countermeasure present. The results conclude that the plastic gabions were the least effective material at reducing pier scour, with an average of 16.3 mm, or a total scour reduction of 22.38%. However, the percentage reduction between the three different types of fill is relatively small, as stone and clothing are 6.2% more effective than the plastic filled gabions at reducing scour. At 12 and 16 mm thicknesses, the gabion models which were most effective were the stone aggregate filled gabions, although

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the results are very similar to both plastic and clothing at these thicknesses. At 8 mm thickness (C8, S8, P8), the reduction in scour was largest for C8, the gabion filled with clothing, as it had a 26.1% reduction in scour hole depth from the original experiment conducted, followed by the stone filled gabion, S8, which reduced bridge pier scour by 17.4%. Eng 2020, 1, FOR PEER REVIEW 15 between 120 s and 150 s; this is due to the deposition of sand sediment into the developing scour hole, therefore decreasing the total scour depth formed. Scour Hole Development When a bridge pier obstructs flow in a stream, a boundary layer separation occurs, and where a point in contact with the bridge pier reverses in direction from the upstream bed in the approach flow, a horseshoe vortex occurs [7]. This was evident in the majority of experiments conducted and caused the formation of a scour hole in front of the bridge pier similar to the scour hole displayed in The plastic gabion, P8, reduced the scour depth surrounding the bridge pier, but was not as successful as S8 and C8. At 12 mm thickness (C12, S12, P12), the use of a gabion model as a scour countermeasure was effective, as the percentage reduction of scour was higher than 34.8% for each fill type used within the gabions. The stone filled gabion, S12, was most effective at reducing scour depth when it had a greater thickness of gabion, although there is not much deviation from the results,

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with P12 and C12 results only having a larger scour depth by 2 and 1 mm, respectively. At 16 mm thickness (C16, S16, P16), the total scour depth results are almost identical to the 12 mm thickness gabions, except for P16, which reduced by 1 mm. Therefore, the percentage reduction of scour remained the same, apart from P16, which increased by 4.3%. Again, the thickness of the gabion models used also impacted the development of scour. At 8 mm thickness, in the worst-performing value of P8, the scour Eng 2020, 1 203 depth increased by 42.86% when compared to P16. There are, however, close similarities between the results of 12 and 16 mm gabion models. The 12 mm gabions had an average scour depth of 14 mm, whereas the 16 mm gabion models had an average scour depth of 13.67 mm, proving that an increase in the thickness of a gabion affects scour. Time appears to have an impact on the cumulative scour depth. At 60 s, all gabion models had accumulated most of the scour depth (with exception to P12). For gabions S8 and C12, the cumulative scour depth decreased slightly between 120 s and 150 s; this is due to the deposition of sand sediment into the developing scour hole, therefore decreasing the total scour depth formed. Scour Hole Development When a bridge pier obstructs flow in a stream, a boundary layer separation occurs, and where a point in contact with the bridge pier reverses in direction from the upstream bed in the approach

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flow, a horseshoe vortex occurs [7]. This was evident in the majority of experiments conducted and caused the formation of a scour hole in front of the bridge pier similar to the scour hole displayed in Figure 15. There was, however, an exception for the gabions of an 8 mm thickness, where in some instances the top layer of the gabion was exposed. Eng 2020, 1, FOR PEER REVIEW 16 Figure 15. There was, however, an exception for the gabions of an 8 mm thickness, where in some instances the top layer of the gabion was exposed. Muzzammil and Gangadhariah [10] investigated horseshoe vortex systems and concluded that the mean size of a primary horseshoe vortex size is approximately 20% of pier diameter. Results from this research project satisfy this finding and, in some cases, is higher than the approximation. Graf and Istiarto [9] substantiate the findings of this research project as a weaker wake vortex system led to the formation of a reduced scour hole size downstream of the bridge pier as well. However, the development of the downstream scour hole may have been adversely impacted when measuring the scour hole depth, as it required placing measuring equipment temporarily behind the bridge pier. This may have led to diversion of flow towards the sides of the flume channel and a reduction in the velocity of the wake vortex, leading to a subsequent reduction in the downstream scour hole size and depth. This phenomenon may also explain the raised level of the sediment downstream of the

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bridge pier when compared to its surroundings shown in Figure 15. A more accurate method of measuring the scour hole depth and size would be to use an acoustic doppler velocity profiler [9], alongside a radar device, or a buried rod system. The effect of sediment has not been considered when investigating the local scour depth, as at uniform sediments, local scour depths are unaffected by sediment size unless it is relatively coarse [39]. As the experiment did not observe measurements for the inflow discharge of sediment (Qs), the research mainly focuses on clear-water scour, where initial Muzzammil and Gangadhariah [10] investigated horseshoe vortex systems and concluded that the mean size of a primary horseshoe vortex size is approximately 20% of pier diameter. Results from this research project satisfy this finding and, in some cases, is higher than the approximation. Graf and Istiarto [9] substantiate the findings of this research project as a weaker wake vortex system led to the formation of a reduced scour hole size downstream of the bridge pier as well. However, the development of the downstream scour hole may have been adversely impacted when measuring the scour hole depth, as it required placing measuring equipment temporarily behind the bridge pier. This may have led to diversion of flow towards the sides of the flume channel and a reduction in the velocity of the wake vortex, leading to a subsequent reduction in the downstream scour hole size and depth. This phenomenon may also explain the raised level of the sediment downstream of the

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bridge pier when compared to its surroundings shown in Figure 15. A more accurate method of measuring the Eng 2020, 1 204 scour hole depth and size would be to use an acoustic doppler velocity profiler [9], alongside a radar device, or a buried rod system. The effect of sediment has not been considered when investigating the local scour depth, as at uniform sediments, local scour depths are unaffected by sediment size unless it is relatively coarse [39]. As the experiment did not observe measurements for the inflow discharge of sediment (Q s ), the research mainly focuses on clear-water scour, where initial scour development occurs proportional to the flow rate (as flow rate increases so does the scour hole depth). After a significant scour depth is reached and there is large sediment movement, then sediment movement of the bed upstream may occur and deposit in the local scour area surrounding the bridge pier [42]. This is known as live-bed scour. Clear-water scour was the main form of scour throughout this experiment, although live-bed scour could have occurred at a sediment depth of 40 mm, as in C16 and S8, where the scour hole depth reduced from 120 to 150 s. This suggests that sediment was deposited into the scour hole from upstream. Whilst this may provide stability to the bridge pier in the short term, it could lead to faster scour development in the future. Summary of Effect of Gabion Fill The results display that, at a sediment depth of 40 mm throughout all thicknesses

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of gabions tested, the most effective fill material is stone, which had an average of 13 mm once the anomaly of S8 was corrected for. Closely followed by the clothing gabion, which had a total scour depth average of 15 mm, and the least effective fill material is plastic, which had an average of 16.3 mm. The gabion filled with stone aggregate was one of the most effective fills (leading to an average 43.5% reduction in scour compared to when no scour countermeasure was installed), which was expected due to the greater weight and larger surface area of the stone aggregate, when compared with other fills. Furthermore, as the stone aggregate had a larger surface area than the other materials tested, this may have put it at an advantage to the other gabion fills in the experiment, although research suggests this is not an issue [43]. The effectiveness of the clothing filled gabion is also prominent, as although it had a lower weight than the stone filled gabion, it produced the same average result over the three different thicknesses tested. The results can be attributed to the fact that the fill material replicates a geotextile (filter cloth) and therefore winnowing (the removal of fine material) of the sand sediment is reduced, leading to a reduction in scour. In this experiment conducted, winnowing could not have occurred, as a uniform sand sediment was selected and winnowing depends on the size of particles of two different sediments [44]. The results at a 50 mm sediment depth suggest that

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the type of fill used in gabion models is largely irrelevant in reducing local bridge scour. The most effective performing gabion fill at this level was the plastic filled gabion, which had an average scour depth of 23.5 mm, once the anomalous result of P16 was removed. Even then, the reduction in scour was only 9.61% from the original test when it was performed using no gabion models. Stone gabion models and the clothing gabion models at all thicknesses had a scour depth average of 24.33 mm, leading to an average reduction of scour of 6.42% from the original no gabion experiment. The difference between the different fills of the gabions is therefore 3.19%, which is a low percentage when considering the total scour depth. Therefore, the type of fill used at a 50 mm sediment depth in gabion models is not a major factor in the development of local scour at bridge piers. Additionally, a valid average of the plastic gabion models has not been calculated, as only two readings have been considered; therefore, the impact of plastic fill in gabions at a 50 mm sediment depth may not be fully representative of its effectiveness at reducing scour. At a 50 mm sediment depth, the average scour depths assessed for the different fill types are skewed, as at 8 mm thickness there is a much larger value of results for the scour depth, and therefore this has impacted the effectiveness of the stone, plastic and clothing materials, which would have had a reduced average scour

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depth if the 8 mm gabion thickness was not considered. To summarise, the results at a 40 mm sediment depth, showed that the stone filled gabion proved to be the most effective at reducing bridge pier scour as expected, due to the heavier weight when Eng 2020, 1 205 compared to the clothing or plastic filled gabions. This is supported by research which found that a heavier countermeasure has a significant effect on the scour depth [35]. Furthermore, the fill of the stone gabions had the largest surface area compared to the clothing and plastic filled gabions, reinforcing findings that the larger the size and area of the scour countermeasure, the greater the reduction in scour [21,22]. The findings were contrary to some research which suggests that the size of the fill has no effect on the behaviour of the gabions [43]. As there are conflicting opinions on whether the size of the gabion impacts the scour depth, further research is required in this area. The results indicate that plastic filled gabions are not as effective as stone and clothing filled gabions, due to its higher average scour depth. However, the advantages of using plastic as a recycled material in construction could lead to environmental and economic benefits; therefore, further research should also be undertaken into the use of plastic as an alternative material. Clothing does appear to be a viable alternative to stone filled gabions, in terms of reducing scour and reducing project costs. Although geotextiles were not used as a fill beneath the gabion

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mattresses, in the experiments of Parker et al. [26], the installation of geotextiles beneath riprap stones led to a 93% reduction in maximum scour depth, which identifies the influence that geotextiles or similar cloth-like materials can have in reducing scour. As previously mentioned, the implementation of clothing into the gabion mattresses will not only reduce the financial overheads of the project, but will also increase the overall sustainability of the project due to the re-use of recycled materials. Further research would need to be conducted to analyse the extent to which the reduced weight of the recycled clothing or fabric can be impacted by the flow velocity, as this could result in dislodging of the gabion due to its lightness. One method that could be used to resolve the issue of dislodging would be to seal the clothing filled gabion to the bridge pier using either an adhesive or a cable, or alternatively, the clothing could be anchored to the channel bed providing reinforcement and protection against failure by uplift. Summary of Gabion Thickness The best performing thickness on average was the largest of the thicknesses tested-gabion which had a thickness of 16 mm-as this thickness of gabion had an average scour depth of 13.67 mm, compared with the thickness of 12 mm, which had an average scour depth of 14 mm, and the 8 mm thick gabion models, which had an average scour depth of 18.67 mm. As all gabion models had a length of 32 mm, it is therefore possible to calculate a length

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to thickness ratio (L/t) for the models, which is provided in Table 7. The 12 mm gabion models had a larger L/t ratio than the 16 mm gabion models (2.67 compared to 2), however the L/t ratios are similar, which may explain the small difference between the two. Although the 12 mm gabion had a larger ratio, this did not correlate with a greater reduction in the total scour of the bridge pier. This contradicts Yoon [1], who concluded that a larger L/t ratio will increase the critical velocity, which is the maximum velocity that the bed material can resist, up to a limiting factor of L/t = 3. This would indicate that the 16 mm thick gabions were not as effective at withstanding critical velocity as the 12 mm gabions; however, the scour reduction was slightly larger in the 16 mm gabions than the 12 mm gabions. This is due to the extended thickness of the 16 mm gabion model providing more embedment for the bridge pier, therefore providing greater resistance to scour in the immediate vicinity of the bridge pier. The least effective thickness of gabion models was 8 mm, and this could be explained due to its large L/t ratio, as L/t = 4 is the largest value considered in the experiment. Highlighting that as the Eng 2020, 1 206 length to thickness ratio of the 8 mm gabions is larger than the limiting value L/t = 3, then the gabions do not have an increased capacity to resist critical velocity, and instead

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provide reduced cover for the bridge pier, adversely impacting scour reduction. Furthermore, the thickness of a gabion must be at least twice the average diameter of the fill [35]. In the experiment conducted, an average fill size used was 5 mm; therefore, when a gabion thickness of 8 mm was used, the T ≥ 2(d 50 ) constraint was not satisfied, which could further explain the lack of effectiveness of the 8 mm thick gabions. The results at a 50 mm sediment depth indicate that varying the fill of the gabion models is largely irrelevant in reducing the total scour depth. In most cases, the effect of the 8 and 16 mm thick gabions resembled the effect of when no scour countermeasures were installed. Additionally, the models S16, C8 and P8 led to the development of scour at a faster rate than the effect of no scour countermeasure installation, until the scour rate plateaued, and the models S16, C8 and P8 equalled the cumulative scour depth when no scour countermeasures were installed. The results at a 50 mm sediment depth corroborate the findings of Yoon [1], as the 12 mm thick gabions have a larger ratio of L/t compared to the 16 mm gabions (by 0.67), which increase the critical velocity and are better suited to reduce scour. Based on Yoon [1], however, the results should also show that at 8 mm thickness, where the L/t ratio is 4 (and the highest), the total scour reduction should be similar to the results of the 12 mm

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gabions; conversely, this is not the case, which suggests that the results do not fully validate the findings [1]. Similar to the results at a 40 mm sediment depth, although the 8 mm thick gabions exceed the limiting factor of 3, this did not increase the capacity of the gabions in the results to resist the scour surrounding bridge piers, but instead led to increased stability of the gabions against failure, and if installed practically, would lead to decreased material costs at the expense of reducing bridge pier scour. To summarise, the thickness of the gabions were an important factor in the reduction of local scour surrounding bridge piers, and at a 40 mm sediment depth, the greater the thickness of the gabion, the greater the reduction of the total scour depth, as a riprap layer (similar to gabions) can resist a higher flow velocity as its thickness increases [44]. Although the greater thickness meant a reduction in the L/t ratio, and therefore contradicts Yoon [1], who suggested this would lead to a reduced capacity to withstand critical velocity, this was not the case at the 40 mm sediment depth for all gabion models tested. However, it is worth stating that the L/t ratios were very similar between 12 and 16 mm thickness gabions (0.67 difference) and the results were also largely similar-a 14 mm average scour depth when compared to 13.67 mm. Therefore, it is difficult to draw conclusions from the results due to the similarity of results. Summary of Effect of Sediment Depth and

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Placement Depth At a 50 mm sediment depth, the most effective fill on average was the plastic filled gabion model, which had an average total scour depth of 22.6 mm compared to stone and clothing models, which both had a scour depth of 24.3 mm. At an increased depth of sediment depth, however, the results are largely ineffective at reducing bridge pier scour, as the total scour depth surrounding the bridge pier with no scour protection is 26 mm; consequently, the gabion models used at this depth are not practical. When the placement depth to pier diameter ratio (Y/b) is larger, then the higher the critical entrainment velocity and the greater the protection of the pier against local scour [1]. When placement depth of the gabion models was closer to the sediment depth at 40 mm, the gabion models were considerably more effective at reducing scour. The results support the findings of Yoon [1], which state that the Y/b ratio is limited to 0.2, and any further increase in the Y/b ratio does not provide further scour protection. This is evident in the results, as the increase in the sediment depth from 40 to 50 mm, and therefore the placement depth, as shown in Table 8, led to an increase in the Y/b ratio; however, because the Y/b ratio exceeded 0.2, no additional scour protection was provided. Additionally, the scour protection provided at the 50 mm sediment depth was reduced when compared to the 40 mm sediment depth. This may imply that increasing the placement depth

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past a certain value may be detrimental to bridge piers as the top level Eng 2020, 1 207 of the gabions is closer to the sediment depth at 40 mm, which suggests there is a reduced stability in the gabions; but with the gabions being placed under a sizeable layer of sand sediment, there is little potential for this to occur, although this substantially reduces the gabions' ability to reduce scour. Summary of Effect of Time on Scour The experiments were conducted in a short time period, over 150 s, with measurements being performed at 30 s intervals. The selection of time period and intervals were based on a trial and error process from when the scour depth increase appeared to slow or stop. As seen from the results, when the sediment depth was 50 mm (with exception to P16, S12, P12 and no gabion), the majority of the scour occurred within the first 30 s of the experiment, whereas when the sediment depth was 40 mm, most of the scour development occurs within 60 s (with exception to P12). Throughout the experiment, scour development was generally maintained or increased progressively as the gabions were tested; however, this was not the case for S8 and C12 at the 40 mm sediment depth, as between 120 and 150 s the cumulative scour depth decreased due to deposition of the sand sediment into the developing scour hole, causing a reduced total scour depth. It is unclear whether further deposition would have occurred if the experiment was conducted for

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a longer time period. However, the deposition of sand into the scour hole may lead to greater impact on the bridge pier's structural strength in the long term. Whilst the test was conducted over 150 s, when combining the results of all the gabion models respectively at both the 40 and 50 mm sediment depths, scour commonly occurred within 30 and 60 s. At a 50 mm sediment depth, the findings support the research of Melville and Chiew [39], who stated that scour depths after 10% of the time to equilibrium vary between 50% and 80% of the equilibrium depth. In terms of this investigation, the majority of scour would be expected to therefore occur within 15 s of the experiment beginning, which is the case at the 50 mm sediment depth, where the majority of scour depth for all models occurred within 30 s of the experiment. However, the lowering of the vertical sluice gate from 30 s onwards would have led to larger depths of water at Y1 and Y2; therefore, as the width of the flume channel remains the same, using the continuity equation V = Q/A, the flow velocity would have decreased as the sluice gate depth was lowered. This could explain the quick development of scour at a 50 mm sediment level prior to the sluice gate being in use. The results differ at the 40 mm sediment depth, and the majority of scour depth occurs under 60 s, which, therefore, does not validate other research into the area [39]. In

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addition to this, due to the lack of time that the gabions were tested for, it is difficult to determine the stability of the gabions. In some studies, after fifteen minutes a riprap layer was stable, but after one hour of testing the riprap failed [44]. This underlines the importance of the need to extend the timeframe of this experiment because although the scour depth accumulation appeared to slow towards the end of the experiment, it could have failed completely when subject to a prolonged time period. Conclusions and Recommendations The use of alternative materials in gabion models in order to reduce local bridge pier scour was investigated in this project. The following conclusions can therefore be stated: • Stone filled gabion models proved the most effective overall at reducing local pier scour, mainly due to the greater weight of the gabion. This is supported by Akib et al. [35]. • Clothing filled gabion models offer a sustainable alternative to stone filled gabions due to the resemblance between the results of the two different gabions, as the clothing acts similarly to a geotextile. • Thickness of the gabions is a major factor in the development of scour; where gabion models had a L/t ratio less than 3, the scour reduction results proved more effective. This supports the findings of Yoon [1]. • The majority of scour development occurred between 20% and 40% of the time the experiment was conducted, offering a different value to that of Melville and Chiew [42], who stated 10%. • Increasing the

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placement depth of the gabion models by 10 mm for all thicknesses of gabions led to large increases in the scour hole depth. Though the Y/b ratio increased, the ratio exceeded 0.2 and therefore the increase in ratio was ineffective; this supports the findings of Yoon [1]. • The effect of changing the gabion fill is largely irrelevant when installed at excessive sediment depths and placement depths as shown in the results at a 50 mm sediment depth. Overall, the accuracy of the results produced were limited due to the experimental set up. The main issue was the disruption of the wake vortices when the downstream scour hole was measured, which may have affected the formation of the scour hole by impacting the sediment surrounding the bridge pier. The sediment depth considered was also excessive to successfully determine the impact that alternative gabion fills can have on reducing bridge pier scour, and placement depths which were relative to Y/b = 0.2 should have been considered. The time frame of the experiment was also too short to determine the prolonged stability of the gabion models. Recommendations and Further Research The research project has helped to identify a gap in existing knowledge on the use of alternative materials in gabion mattresses. Additional research could be performed reinvestigating the methodology used, with various parameters from the experiment altered. This may include increasing the time period for considerably longer, such as 24 h, and reducing the placement depth of the gabions so that the tops of the gabion mattresses are

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immediately below the sediment depth. Further research could also investigate the combined use of alternative materials (vegetation) with other scour countermeasures, such as collars. This project was conducted in uniform sediment conditions, which does not affect scour formation; therefore, further research may consider the use of coarse sediment, which may lead to abrasion of the gabion mattresses, as well as affecting the scour hole development.

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A modified ecological footprint method to evaluate environmental impacts of industrial parks Industrial parks have been playing a crucial role on driving regional economic development, but also been exerting significant impacts on natural ecosystems due to intensive resource consumption and waste emission. Ecological footprint method is a tool for analyzing the impact of human activities on environment, which has been applied in many fields. Most of the researches applying ecological footprint are conducted on large-scale objects, such as nation and globe. The ecological footprint analysis on the scale of the industrial park, however, is limited. This paper presents a modified ecological footprint accounting model, and applies it to appraise the environmental impact of an industrial park-Hefei economic and technological development area. Results show that the ecological footprint (8.87E+05 gha (global hectares)) far exceeds the ecological capacity (4.82E +04 gha), meaning that the ecological footprint is 18.4 times of the ecological capacity in the study park. In addition, the ecological footprint reduction caused by eco-industrial development in the study industrial park is quantified by ecological footprint model. The ecological footprint has been reduced by 15.9%, from 1.06E +06 gha to 8.87E+05 gha, which signifies an obvious environmental performance and economic benefits. Based on this study, the utilization of energy and material could be optimized in industrial park to reduce the influence of industrial activities on natural ecosystem. This paper provides a basis for an industrial park’s environmental management and decision making. Introduction Among various human activities promoting economic growth in China, industrial parks are themajor contributor. In

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the past 30 years, China established more than 2000 industrial parks, which accounted for more than 60% of gross national industrial output value and more than 50% of GDP (Bao, 2013). In 2014, the GDP growth rate of industrial parks, 29.1%, prominently surpassed that of the national average, 7.4% (CADZ, 2014). Industrial parks play an important role in driving the regional economy, but it has a huge impact on natural environment due to intensive industrial activities. It is very important for industrial parks' sustainable development to assess the environmental impact caused by resource consumption and waste emissions. Market prices or other monetary appraisal methods are untrustworthy ways for indicating the long-term viability of ecosystems that provide goods and services such as topsoil evolution, climate-related security, biodiversity, fuel, and feed. The ecological footprint (EF) measures demands for natural resources and pressures on ecosystems (Wackernagel and Rees, 1998). As an effective assessment tool, ecological footprint can measure human's resources throughput and evaluate the actual depletion of natural resources, and thus appraise the gap between humanity's demand and natural services supply (Van Kooten and Bulte, 2000). The original EF concept, introduced by Rees (1992), is that every individual, process, activity, and region has an impact on the Earth, via resource usage, waste generation and the use of services provided by nature. These impacts can be converted to biologically productive area which can be quantified. Ecological footprint signifies the land area required to maintain present levels of resource consumption and waste discharge by a given population. It provides an intuitive

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framework for understanding the ecological bottom-line of sustainability, and then stimulates public debate, builds common understanding, and suggests a scheme for action. Ecological footprint makes the sustainability challenge more transparent-decision makers have a physical criterion for rating policy, project or technological options according to their ecological impacts (Wackernagel and Rees, 1997). Ecological footprint is closely related to the concept of ecological carrying capacity, which is the population of a given species that can be supported in a defined habitat without permanently damaging the ecosystem (Catton, 1986;Arrow et al., 1995). If an EF is larger than the corresponding ecological carrying capacity, 'ecological deficit' occurs (Wackernagel and Rees, 1997), indicating the ecological capacity barely supports sustainable development. EF analysis has been used to study many systems of different scales, including regions (Wackernagel et al., 2006;Wackernagel and Yount, 1998), nations (Lenzen and Murray,2001;Begum et al., 2009;Wang et al., 2017), and even the whole globe (Galli et al., 2012;Wackernagel et al., 2002), in which the national EF analyses are popular due to data availability. The national scale data needed in EF estimation is easy to get from the international organization such as FAO (Food and Agriculture Organization) or UN (United Nations). Many EF analyses affirmed that most countries with advanced economies were not sustainable (Kitzes et al., 2007;Wackernagel et al., 1999;Wackernagel et al., 2002). Globally speaking, Wackernagel et al. (2002) concluded that the total ecological footprint of human beings in a given time surpassed the regeneration capacity of the Earth's resources. Some EF analysts claimed that if a region's ecological

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footprint was larger than its ecological carrying capacity, it would impair the regenerative capacity of the local natural assets (Rees and Wackernagel, 2008;Wackernagel et al., 2006). The region therefore must import external resources, and strengthen technological innovation to reduce the consumption of local resources (Opschoor, 2000). In addition, EF is widely applied in various fields. Many scholars studied the aquaculture industry by EF analysis (Gyllenhammar and Håkanson, 2005;Roth et al., 2000;Berg et al., 1996). Gössling et al. (2002) and Castellani and Sala (2012) applied EF analysis to tourism, and both found that ecological footprint was an effective tool in assessing the sustainability of tourism; Wright and Drossman (2002), and Flint (2001) conducted EF analysis on schools respectively, and identified those components which accounted for the large parts of the footprint and thus provided the opportunity for effective management. Through the study of the EF of many products and services consumed in the western economy, Huijbregts et al. (2008) found that the ecological footprint of most of the products was dominated by the non-renewable energy consumption. Some researchers have applied EF method to the analysis of industrial parks (Liu et al., 2015a;Chen et al., 2013). These researches are however limited and not comprehensive in EF accounting. Compared to other sustainability assessment methods such as LCA or emergy method (Guinée,2002;Liu et al., 2014;Odum, 1996), ecological footprint method is more intuitive and more transparent. Since EF uses a land area (global hectares) to reflect the human impact, people will understand this concept more easily. LCA can analyze the environmental

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impact but it cannot conduct comparison with the carrying capacity (Guinée, 2002). Emergy method could quantify the resources consumption by a unified physical unit, but it is not directly comparable with local environmental capacity (Chen et al., 2017;Liu et al., 2014). EF method can measure ecological footprint and ecological carrying capacity, and conduct comparison between them. Promoting eco-industrial development (EID) by the principles of industrial ecology (IE) provides a way to approach sustainable development in industrial park. Industrial ecology is a concept for studying the sustainable development of environmental and economic systems (Chertow, 2000;Chertow, 2007). According to the United Nations Environment Programme (UNEP, 2004), IE is "the systems-oriented study of the physical, chemical, and biological interactions and interrelationships both within industrial systems and between industrial and natural ecological systems." Eco-industrial park (EIP) is one of the important practical forms of IE. Industrial symbiosis (IS), in the form of eco-industrial parks, provides a method to combine local economic development with advantageous environmental outcomes (Chertow and Ehrenfeld, 2012). Gathered according to principles of industrial ecology, the functions of industries in an EIP complemented each other by improving outputs, saving resources and energy, and abating environmental impacts (Yu et al., 2014). The eco-industrial development practices involved physically exchanges between one another of raw material and wastes/by-products and sharing/consolidating/coordinating the management of utilities and infrastructures such as water supply, energy utilization, pollutant emissions, and distributions (Gibbs and Deutz, 2007;Yang and Feng, 2008). Since the success of the Kalundborg industrial symbiosis in Denmark (Jacobsen, 2006), EIPs have emerged around the world

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(Farel et al., 2016), including Europe (Gibbs and Deutz, 2007), the United States (Gibbs and Deutz, 2005), Australia (Roberts, 2004), Korea (Behera et al., 2012), and China (Zhang et al., 2010;Yu et al., 2015). Chinese EIPs incorporate the principles of industrial symbiosis, such as infrastructure sharing and wastes/byproducts exchange. Also, they adopt varied environmental management tools, including cleaner production and energy audit, to promote eco-industrial development and improve environmental performance (Shi et al., 2012a,b;Tian et al., 2014;Yune et al., 2016;Liu et al., 2015b). In industrial ecology, the industries in a park formed a community and each industry occupied a niche. If the community is symbiotic, the energy and resources they used, products they produced, and the wastes they generated would form an ecological echelon and the resources and energy flowed through from bottom up. The functionalities, benefits, and impacts of the industrial park community therefore should be characterized in terms of flows and balances of energies and resources that were present in different forms and were expressed in different units. In this study, from an ecosystem perspective, a modified EF accounting method was proposed, as an unbiased and comprehensive tool, to evaluate the sustainability of one industrial park and the performance of eco-industrial development. Complete EF accounts of an industrial park measure the biologically productive space occupied exclusively to provide all the resources which the industrial park consumes and to assimilate all the wastes the park generates. This study aims to explore the natural impact of the industrial activities at an industrial park based on modified

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EF analysis. In the following, Section 2 introduces an innovative component EF method which can investigate the whole impact of industrial park. Section 3 describes a case study of a typical industrial park in Hefei. Section 4 calculates the ecological footprint, ecological capacity and ecological deficit of the study park, and discusses EF reduction due to the implementation of eco-industrial development. Ecological footprint estimation The original methodology for calculating ecological footprint, developed at the University of British Columbia, is outlined in earlier publications (see for example Rees (1992) and Wackernagel and Rees (1998)). Ecological footprint accounts express the use of built-up areas, and the consumption of energy and renewable resources-crops, animal products, timber, and fish-in standardized units of biologically productive area, termed global hectares (gha). One global hectare is equal to 1 ha with the average productivity of the 11.4 billion bioproductive ha. Two conversion factors-equivalence factor (see Table 1) and yield factor-convert each of the biologically productive areas from hectares into global hectares. Equivalence factor represents the relative productivity of a particular type of land to the world average productivity of all land. Yield factor accounts for differences between countries in productivity of a given type of land. For this study, the equivalence factors are cited from the work presented by Wackernagel et al. (2004a). The global average productivity is applied in this study so the yield factor is not needed for this ecological footprint calculation. The conventional EF analysis does not take into account the nonrenewable resources and water resources (Wackernagel et al., 2004b).

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The non-renewable and water resources, however, are important powers to drive industrial production in the industrial park Wang et al., 2006). Therefore, a modified EF analysis was proposed in this study to count these resources, so as to reflect the real environmental impact of industrial processes in the industrial park. In the case of industrial park, the ecological footprint of renewable resources and energy (A 1 ) can be calculated as follows: where R i is the amount of consumption of renewable material i; E j is the amount of consumption of energy j. NP i and EP j are productivities per hectare of the particular land corresponding to material i and energy j, respectively; f i is equivalence factor of the land corresponding to renewable material i, f j is equivalence factor of the land corresponding to energy j. In the conventional EF method, the choice of the account is mainly concerned with the consumption of biological products and energy products. The non-renewable resources producing so much ecological footprints in industrial production should be calculated in this study. Fish land is one of the six main types of production land, which is one kind of ecological footprint account. However, biological production is only one of the functions of water. Water resources have multiple functions which cannot be replaced in the maintenance of the ecological environment and in the process of social life and production. Throughout the research for theory and practice of ecological footprint previously, the estimation of water resources was ignored. Therefore, water resource

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needs to be considered in the EF calculation. The pollutants discharged into the environment need to occupy a part of biologically productive land, corresponding to a certain ecological footprint, which cannot be ignored. In this case, the EF of various kinds of pollutants, which is ecological productive land occupied to assimilate waste to meet with relevant requirements, is calculated to make the EF accounting results more reasonable and comprehensive. The EF (A 2 ) of the non-renewable resources, water resources, and waste assimilation should be calculated where N m is the amount of consumption of non-renewable resource m, e m is the ecological footprint per unit of resource m, Q is the amount of water consumption, Y w is the average global production capacity of water resources per hectare. e q is equivalence factor of water. W n is the amount of waste n, WA n is the waste assimilation capacity per hectare of the land used to assimilate waste n. f n is equivalence factor of the land used to assimilate waste n. The total ecological footprint of an industrial park can be calculated from Eq. (3) (3) Ecological capacity accounting In the current study, five types of land have been taken into account. In addition to built-up land, arable land, pasture land, and forest, water area is considered as a new added item different from "fish land" in previous studies. No sea area exists in an industrial park. The ecological capacity (EC) of the industrial park is calculated as follows: where L j is

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area of j-type land, EF j is the corresponding equivalence factor of j-type land. 2.3. Case study park 2.3.1. Description and data collection Hefei economic and technological development area (HETDA) was chosen for case study. It covers an administrative area of 258 km 2 at present, including separate sections for built-up land, forest, pasture land, cropland and water bodies (Nanyan lake, Feicui lake, etc.) (HETDA, 2014). Over the past two decades, HETDA has established 4 pillar industries (home appliances, equipment manufacturing, automobile and parts, fast-moving consumer goods) and 4 emerging industries (electronic information, new materials, bio-pharmaceuticals, industrialized housing). Examples of famous companies include Hitachi, Midea, Haier, Gree, JAC, Navistar, Unilever, Coca-Cola, Unipresident, etc. The statistical yearbook of HETDA (HETDA, 2014), government report, natural resources and environment statistical yearbook, and environmental reports of environmental protection bureau and key companies within HETDA were collected for extracting useful information and data. 180 survey sheets were sent to enterprises and organizations within HETDA to gather the material/energy consumption information and 153 valid ones were recovered. We reviewed the primary data and validated their authenticity and accuracy through field investigations and in situ observations to ensure the reliabilities and trustworthiness of the data. The year of 2014 is defined as the base year. Eco-industrial development Since Hefei is a famous tourist city and has several historical heritages, maintaining a clean and pleasant environment in Hefei's largest industrial park (HETDA) is thus beneficial to its economic well-being. Given these regional characteristics, HETDA has a great desire to improve the park's eco-efficiency and

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environmental quality overall. Therefore HETDA applied for the national title "National demonstration eco-industrial park" (NDEIP) in 2010 and intended to pass the national onsite inspection organized by MEP (Ministry of Environmental Protection), MOC (Ministry of Commerce), and MOST (Ministry of science and technology) in 2015. After several years' eco-industrial development, HETDA has made some achievements. Fig. 1 shows the holistic eco-industrial structure in HETDA. Under the NDEIP project, the wastewater pipelines were extended to 287 km and the wastewater treatment capacity reached to 8.513E+7 t/yr. Several plants have been rejected to settle in HETDA due to large energy consumption and environmental decay. Over 50 coal-burning boilers have been phased out due to their low energy efficiency and high emissions. All the 24 key polluting companies have passed cleaner production audits and adopted over 500 cleaner production options in order to promote the pollution prevention. Jinyuan thermal power plant, as one role model, adopted the wet limestone-gypsum flue gas desulfurization process and the low NO x emission combustion technology that conserved energy and reduced emissions (HETDA, 2014). More importantly, in order to propel EID, HETDA determined to promote by-product exchanges among the four main industrial clusters and four emerging industries. Several synergy opportunities have been identified and implemented through the NDEIP construction efforts. For instance, fly ash and slag produced from Jinyuan thermal power plant become feed stock of building material producers in manufacturing construction material. Another example is that scrap steel and iron generated by local equipment manufacturing were reused as raw materials. From the view

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of infrastructure sharing, many enterprises used the steam from the local cogeneration power plant thus avoided using their own boilers. Table 2 shows the ecological footprint of components including raw material use, energy consumption, and waste assimilation in the study park. The total ecological footprint of HETDA is 8.87E+05 gha through summing all input items. The largest EF component was non-renewable resources consumption (N), which accounted for 70.09% of the total EF with a value of 6.22E+05 gha; the second and the third largest EF components were energy consumption (E) and renewable resources consumption (R), which were 16.79% and 7.15% of the total EF, respectively. Waste assimilation occupied a certain proportion of the total EF (W, 5.98%). Ecological footprint and ecological capacity Steel and iron occupied the largest EF (5.10E+05 gha) in the nonrenewable resources. While in the renewable resources, the EF of maize was the largest component (2.67E+04 gha). Coal consumption occupied the largest EF among the 8 categories of energy, with a value of 1.33E+05 gha. NO x occupied the largest EF in the waste assimilation with a value of 4.69E+04 gha. EF intensity, defined as the ratio of the EF to the economic output, is used to depict the resource consumption intensity. To produce per 10 4 RMB needs to consume 0.144 gha EF of resources at HETDA. The ratio of GDP to EF in the study area is 6.92E+04 RMB/gha, which can be regarded as an attempt to show the close relationship between the "land demand" and economic output, as discussed by

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Farber et al. (2002) concerning the relationship between available resources and economic output. Table 3 shows how much ecological capacity is available within the study park. According to HETDA (2014), the study park has an area of 258.57 km 2 , in which the industrial land area is 42.34 km 2 , built-up land occupies an area of 62.88 km 2 , arable land area is 74.46 km 2 , pasture land area achieves 44.68 km 2 , and forest area occupies 29.78 km 2 . In addition, HETDA has a water area of 4.43 km 2 . The land for biodiversity was not taken into account in the study since an industrial park is a special region for industrial agglomeration. Totally the ecological capacity of this industrial park is 4.82E+04 gha. Ecological deficit As the ecological footprint and the ecological capacity available within HETDA are both measured in the same unit, they can be compared directly. If the ecological footprint is larger than the available ecological capacity, an 'ecological deficit' occurs. Results show that HETDA requires land appropriation 18.7 times of the actual ecological capacity of itself, and the industrial park has undergone an ecological deficit of 8.39E+05 gha. In general, the EF of industrial activities has far exceeded the carrying capacity at HETDA. The ecological deficit per hectare is 32.94 gha. Totally, HETDA can (with its own ecological capacity) only supply 5.4% of its demand based on the current production level. Consequently, the vast majority of resources at HETDA need to be imported from

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outside. The assimilation of waste produced from the park has a certain EF of 5.30E+04 gha, which is larger than carrying capacity of this park. The potential for increasing HETDA's total productive area is not great. Thus the only possibilities for increasing HETDA's biocapacity depend on boosting yields on already existing productive areas and optimizing the land use. Discussion on EID and policy implications In recent years, eco-industrial development at HETDA primarily includes cleaner production, infrastructure sharing and by-products (or wastes) exchange. Wastes that can be reused, including wastewater, residual heat, fly ash, slags, steel, and pig iron, are mainly from the cogeneration power plant, equipment manufacturing, auto and electronic enterprises. Main EID activities occur between local cogeneration power plant and other tenant companies. First boiler steam from Jinyuan thermal power plant is being used for fast-moving consumer goods enterprises, construction materials production, and equipment manufacturing, etc., with a certain amount of 1.19E+06 t per year. Then fly ash from Jinyuan thermal power plant is being used for cement production, with a total amount of 7.89E+04 t per year, which can replace the same amount of cement per year. Finally, the slags from thermal power plant are being used for brick and cement production, with a total amount of 1.42E+04 t per year. Other EID activities also include scrap steel and pig iron reuse and occur among local manufacturing, electronic and metallurgical firms, with a total amount of 9.54E+04 t per year. In addition to the practices between enterprises, from the viewpoint of inner-enterprise, enterprises at

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HETDA make efforts to promote EID projects through technological innovation. Unilever Company developed biomass (straw) combustion boiler technology to replace the natural gas with straw, which conserved energy and improved local environment. Burning straws, in comparison to combusting natural gas, reduced the energy costs by 50%, decreased pollutions associated with open burnings significantly and annual greenhouse gas emissions by 15,000 t, and eliminated the needs of landfilling solid wastes (HETDA, 2014). Through technological innovation, Jac-Navistar Diesel Engine Co., Ltd. can recover the iron in the chip liquid which avoids wasting useful materials and reduces the pollutant emissions. Waste recycling is then considered by ecological footprint analysis from the full perspective, so that the holistic picture including saving virgin materials can be presented. All the EID efforts above can generate significant benefits on saving raw materials and reducing pollutant emissions at HETDA. Therefore the EF of HETDA is reduced due to eco-industrial development (see Table 2 Ecological footprint accounting for HETDA, with and without considerations of EID (Eco-industrial development). Nowak (1994); 12-Electricity's ecological footprint is largely attributed to the fossil energy land. In order to avoid double counting, the ecological footprint of electricity should be got from the calculation of Hydro-electricity consumption. Table 4). As shown in Fig. 2, the EF for waste assimilation makes the largest reduction degree from 1.50E+05 gha to 5.30E+04 gha, with a decreasing rate, 64.61%. The non-renewable resources have a total EF of 6.22E+05 gha, reducing 9.45% of the original EF without EID. EID makes the EF of energy consumption decrease by

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4.19% from 1.55E +05 gha to 1.49E+05 gha. The EF of renewable resources decreases from 6.35E+04 gha to 6.34E+04 gha, which is a little change. The reason why the EF of waste assimilation decreases to the largest degree among the four categories is that a lot of waste was indeed reused for other production processes. In this park, the ecological footprint of nonrenewable inputs, renewable resources consumption, energy use, and pollutants assimilation, can be reduced by 6.49E+04 gha, 1.19E +02 gha, 6.52E+03 gha and 9.68E+04 gha, respectively, with the implementation of eco-industrial development. In general, EID reduced the total EF of the industrial park by 15.9% from 1.06E+06 gha to 8.87E+05 gha, signifying a great decrease of pressures on environment. The ecological deficit of HETDA decreased by 16.71% due to ecoindustrial development. Steel had the largest EF in non-renewable resources, coal made the largest EF in energy, and the sum of NO x and SO 2 occupied the largest EF in waste. Hence, technologies of steel and iron recycling and reuse need to be innovated. The energy structure should be adjusted to reduce the consumption of coal, and increase the use of renewable (green) energy. Last but not least, NO x and SO 2 should be reduced by innovated technologies of cleaner production and end-of-pipe treatment. In this study, we select the most relevant specific EF from the existing sources. Although we are using the best available data, the results comprise uncertainties and official statistics and EF data sources do not report error boundaries in data,

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so it is impossible to undertake a formal and rigorous uncertainty analysis. Policy suggestions have been proposed to improve the sustainability of the industrial park. First, formulating or improving resource depletion taxes and pollution charges can be effective in reducing EF. They provide incentives for firms to save resources and eliminate emissions by adjusting their decision making; second, the industrial park should continue to enhance eco-industrial development including optimizing the land-use pattern and modifying the industrial structure to achieve sustainable development. In addition, compensation of carrying capacity is another important aspect. The most effective strategies for compensating carrying capacity are taking options of renewable electricity generation and plantations. Specifically, options such as the reforestation of already degraded land, the refurbishment of actual irrigation and water supply reservoirs with hydroelectric facilities, and the installation of solar water heaters and solar cells on rooftops are preferred in regard to land disturbance, since these measures have no direct effect on land condition. Concluding remarks Human activities have an impact on the Earth because they consume the products and services of nature (Wackernagel et al., 1999). Industrial parks, consuming large quantities of materials and releasing a great number of pollutants, have a huge impact on natural environment. Study on resources consumption or pollutants emissions embodied in industrial activities will significantly help us to understand how industrial parks interact with their natural environment. This paper presents the structure of quantifying systematically the ecological footprint based on component frameworks that could be also used in other areas study. Compared to the conventional

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EF analysis, this method added the accounts of the non-renewable resources, water resource to reflect the real status of an industrial park. The modified method is then applied to the industrial system of HETDA. Research results show that the ecological footprint of HETDA was 8.87E+05 gha, which was 18.4 times of its ecological capacity, and the ecological deficit achieved 8.39E+05 gha. After the implementation of eco-industrial development, ecological footprint of non-renewable resources, renewable resources, energy and pollutants, was saved by 9.45%, 0.19%, 4.19% and 64.61%, respectively. Overall, eco-industrial development reduced the total ecological footprint of the industrial park by 15.9% (from 1.06E+06 gha to 8.87E+05 gha), which meant a great decrease of impact on environment. The ecological deficit of this study park was reduced by 16.71% (1.68E+05 gha) accordingly. However, there are some limitations in this ecological footprint analysis. Although the principle of EF analysis is fairly simple and intuitional, the data collection process is a time-consuming work and sometimes it is very difficult to complete detailed understanding and adequate collection of the data. Furthermore, although equivalence factors, land productivity and ecological footprint per unit for different items are available in published literature, they are location and process specific and may not fit properly a different investigated case. We collect the most relevant per unit EF and other parameters from the existing sources. There might be numerous opportunities for extending this work from providing greater insights in improving equivalence and yield factors to let them be more fit for relatively small scale, which based on entirely

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localized data and accurate accounting procedures. This EF framework offers an intuitive natural capital evaluation for an industrial park with which industrial production demands can be compared with local nature's available supply for the industry use. EF is an accounting tool that can keep track of resources consumption in an ecologically meaningful way. It gives us, therefore, a realistic painting of the industrial park in ecological terms. This is what we need to know to achieve sustainable development, securing quality of industrial production within the means of nature. It requires promoting eco-industrial development, and improving industrial production efficiency while reducing ecological footprint. This study could provide scientific basis and direction for optimizing environmental management in industrial parks.

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Do ADHD-impulsivity and BMI have shared polygenic and neural correlates? There is an extensive body of literature linking ADHD to overweight and obesity. Research indicates that impulsivity features of ADHD account for a degree of this overlap. The neural and polygenic correlates of this association have not been thoroughly examined. In participants of the IMAGEN study, we found that impulsivity symptoms and body mass index (BMI) were associated (r = 0.10, n = 874, p = 0.014 FWE corrected), as were their respective polygenic risk scores (PRS) (r = 0.17, n = 874, p = 6.5 × 10−6 FWE corrected). We then examined whether the phenotypes of impulsivity and BMI, and the PRS scores of ADHD and BMI, shared common associations with whole-brain grey matter and the Monetary Incentive Delay fMRI task, which associates with reward-related impulsivity. A sparse partial least squared analysis (sPLS) revealed a shared neural substrate that associated with both the phenotypes and PRS scores. In a last step, we conducted a bias corrected bootstrapped mediation analysis with the neural substrate score from the sPLS as the mediator. The ADHD PRS associated with impulsivity symptoms (b = 0.006, 90% CIs = 0.001, 0.019) and BMI (b = 0.009, 90% CIs = 0.001, 0.025) via the neuroimaging substrate. The BMI PRS associated with BMI (b = 0.014, 95% CIs = 0.003, 0.033) and impulsivity symptoms (b = 0.009, 90% CIs = 0.001, 0.025) via the neuroimaging substrate. A common neural substrate may (in part) underpin shared genetic liability for ADHD and BMI and the

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manifestation of their (observable) phenotypic association. Introduction Attention deficit hyperactivity disorder (ADHD) is a neurodevelopmental disorder with a typical onset during childhood, but also shows mixed patterns of continuity and remittance, along with an adulthood onset [1]. Previous studies indicate an association between adult ADHD and being overweight and, in extremis, obesity [2,3]-conditions which are relatively common and have marked longterm health effects [4,5]. Research has identified factors contributing to the comorbidity between ADHD and obesity, including fetal programming, psychosocial stress, and factors directly related to energy balance, reduced physical exercise and sleep patterns alterations [6]. The bulk of current research has focused on how neuropsychological impairments (e.g., impulsivity) associated with ADHD may increase dysregulated and excessive eating [2,3]. Importantly, neural and genetic liabilities may be important components underlying the phenotypic association between ADHD and overweight/obesity [6]. With regard to neural correlates, a recent ADHD ENIGMA mega-analysis [7] reported smaller subcortical volumes for These authors contributed equally: Edward D Barker, Alex Ing ADHD (n = 20,183) compared to controls (n = 35,191) in the accumbens, amygdala, caudate nucleus, hippocampus and putamen. Importantly, some of these brain areas are involved in inhibitory control and reward-related pathways [7]. Neuroimaging studies in individuals who are overweight or obese have identified similar regions implicated in inhibitory control and reward-related pathways [8], including the amygdala, hippocampus and prefrontal cortex as well sensory areas (precentral gyrus) that could relate to food cues [9]. Genome wide association studies (GWAS) have identified susceptibility loci for ADHD [10] and obesity [11]. A polygenic risk score

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(PRS)a cumulative genetic risk profile from across the genomederived from the ADHD GWAS [10] showed associations with obesity-related indices of body mass index (BMI [12]), waist-to-hip ratio, childhood obesity, HDL cholesterol and Type 2 diabetes. Another study [13] using the ADHD PRS reported positive associations with BMI, depression and substance use, with an inverse relationship with numeric reasoning, suggesting genetic overlap with neurocognitive performance (see also [14]). Indeed, with regard to neurology, loci from the ADHD GWAS [10] have been associated with both ADHD risk and lower intracranial volume, as well as the amygdala, caudate nucleus and putamen [15]. PRS approaches have been applied to brain imaging studies. Although this has yet to be done with ADHD and obesity simultaneously, a PRS based on the recent ADHD GWAS [10] associated with smaller caudate volume [16]. The use of PRS in schizophrenia has been associated with abnormalities in both brain structure [17] and function [18]. With regard to structure, Neilson et al. [17] reported an association with bilateral frontal gyrification, which is a hypothesized neural endophenotype of schizophrenia [19]. These findings suggest that a better understanding of the relationship between ADHD and overweight/obesity may be gained by using an approach that incorporates both genetic and neural variation. We used the rich dataset of the ongoing IMAGEN study, comprising impulsivity symptoms, BMI, genome-wide loci and whole brain structural and functional neuroimaging measures at age 19. Firstly, we aimed to examine associations between PRS scores and phenotypes for ADHD and BMI, to assess genetic and phenotypic relationships between these

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traits. Secondly, we aimed to assess the associations between the PRS scores for ADHD and BMI, whole-brain structural variation, as well as a functional neuroimaging measure that assesses rewardrelated impulsivity. We were also interested in examining the degree to which the PRS scores of ADHD and BMI associated with the phenotypic measurements of impulsivity symptoms and BMI via the identified neural imaging substrate (a mediational model). We had no a priori hypotheses about associations between the PRS scores and brain regions; we ran the analyses in an exploratory manner. Participants We conducted all analyses on individuals drawn from the IMAGEN study (www.imagen-europe.com), a large-scale imaging genetic study aimed at identifying genetic, neuroimaging, and behavioural bases of individual variability in psychiatric disorders. Genetic data was derived from blood samples collected at the age of 14, while clinical, physical and neuroimaging data analysed in the present study were collected at the age of 19. Psytools software (Delosis Ltd, London, UK) was used to conduct the behavioural characterization via its internet-based platform. The assessment battery of questionnaires and cognitive tasks was self-administered both in participants' homes and at the neuroimaging facilities. The study was approved by local ethics research committees at each site. Written informed consent was obtained from all participants as well as from their legal guardians. Measures. Impulsivity symptoms at age 19 were assessed using self-reported scores taken from the well-validated Barratt Impulsivity Scale (BIS) [20]. The BIS is a questionnaire that is widely used to assess trait-impulsivity in a variety of studies including ADHD [21], neuroimaging

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[22], personality [23], over-eating [24] and in relation to genetic influence and criminal behaviours [25]. At the time the study was conducted, the IMAGEN consortium had BIS data for 1319 individuals at 19 years-old. Body mass index (BMI) BMI at age 19 was derived from height and weight measurements. Height was measured using a standard protocol to the last complete centimeter, weight was measured to the nearest 100 g. BMI was calculated as weight (kg)/height(m 2 ). BMI values were recorded for 1347 subjects at the time the study was conducted. We excluded 114 participants who either were underweight (BMI < 18.5) extremely overweight (BMI > 50). Genetic data After quality control, 1982 cases were included in our sample totalling 506,932 SNPs available for PRS. Population stratification was controlled for in all analyses via the use of the first eight principal components of the genetic data, which were used as covariates. Full details on acquisition and initial processing are given in the supplementary materials of this paper. MRI data In this investigation, we used voxel-based morphometry measures of grey matter derived from T 1 weighted MRI acquisitions and activation maps derived from the Monetary Incentive Delay (MID) task, to examine neural responses to reward anticipation and reward outcome. Full details on the MRI acquisitions [26] pre-processing [27] and confounds used in the analysis are given in the supplementary materials of this paper. A Task Based fMRI Acquisition of the Monetary Incentive Delay (MID) task was used to examine neural responses to reward anticipation and reward outcome

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[28]. The task consisted of 66 10-s trials. In each trial, participants were presented with one of three cue shapes (cue, 250 ms) denoting whether a target (white square) would subsequently appear on the left or right side of the screen and whether 0, 2 or 10 points could be won in that trial. After a variable delay (4000-4500 ms) of fixation on a white crosshair, participants were instructed to respond with left/ right button-press as soon as the target appeared. Feedback on whether and how many points were won during the trial was presented for 1450 ms after the response. Using a tracking algorithm, task difficulty (i.e., target duration varied between 100 and 300 ms) was individually adjusted such that each participant successfully responded on~66% of trials. Based on prior research suggesting reliable associations between ADHD symptoms and fMRI bloodoxygen-level dependent (BOLD) responses measured during reward anticipation, the current study used the contrast 'anticipation of high-win vs anticipation of no-win'. Statistical analyses The analyses proceeded in three steps (code used in statistical analyses is available upon request). In Step 1, PRS scores were created for ADHD and BMI and we examined associations between the scores and phenotypic measures. We also calculated associations between the ADHD and BMI PRS scores themselves, in order to investigate a potential genetic comorbidity between ADHD and BMI. To derive the ADHD PRS, summary statistics were downloaded from the Psychiatric Genomics Consortium (http://www.med.unc.edu/pgc/results-and-downloads; 20,183 cases and 35,191 controls, all European descent). To calculate the BMI PRS, GWAS summary statistics from 339,224

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European descents were downloaded from the GIANT Consortium (http://portals.broadinstitute.org/ collaboration/giant/index.php). Deriving a PRS necessitates the use of a significance threshold for inclusion of SNPs in the calculation of the score (e.g., all SNPs associated at p < 0.05). In investigations where the researcher is only interested in the relation between the score and the phenotype, it is possible to vary that threshold, and select that which results in the highest variance explained between the PRS and the phenotype [29,30]. However, in the present investigation, we were also interested in both the PRS scores themselves, and in their relation to functional and structural neuroimaging measures. In this case, varying the threshold for SNP inclusion in the PRS scores for ADHD and BMI, respectively, can lead to overfitting on the phenotype of interest [30]. Given the nature of our research question, which involves multiple phenotypes and multiple brain markers, this overfitting could lead to circularity problems in further analyses [31]. Using multiple PRS scores also poses a problem with multiple comparisons: if several PRS scores are calculated on the same phenotype, a correction must be carried out over these tests to ensure significance [30]. We therefore chose to use a nominal threshold of p = 0.05 for the inclusion of SNPs in the calculation of the score. This approach avoids both overfitting and multiple testing. All genetic data processing and analyses were performed using the R package PRSice [15] and PLINK [17]. In order to minimise the statistical assumptions necessary for valid inference, all significance levels reported here

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were ascertained using permutation testing. As we are explicitly looking for comorbidities between different data types, and the sPLS analysis only identifies positive associations, all significance tests were one-sided. In Step 2, we investigated whether ADHD and BMI share a common underlying neural substrate. We used a sparse formulation of partial least squares (sPLS) for this purpose [18,19]. This method is designed to establish associations between multiple sets of variables by finding the weighted sum of variables in each set, which correlate maximally with the weighted sum of variables that are connected via a path diagram (see Supplementary Figure S1). We used five-fold cross-validation to quantify the strength and significance of the associations of individual PRS scores and phenotypes, with the VBM and MID measures they were connected to via the path diagram [32]. Although PLS methods are very powerful, results can be difficult to interpret, as all variables contribute to associations between data-views. This is particularly problematic with neuroimaging data, which is high dimensional. It would be useful to know which neuroimaging features were associated with PRS scores and phenotypes of impulsivity and BMI. For this reason, we used a method that induces sparsity by setting some PLS weights to zero through the application of an L 1 penalty, applied under resampling [33,34]. Through this approach, one can identify weighted sets of brain regions that are associated with the PRS scores and phenotypes. This set of brain regions may therefore be considered as an endophenotype for ADHD and BMI. We used a resampling procedure to

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ensure that the PLS approach only retained features that were robustly associated with phenotypes and genetic measures [33]. Significance was ascribed using a permutation testing procedure. A detailed description of the exact analysis approach used is detailed in the Supplementary Materials. In all analyses, we controlled for genetic population stratification (i.e., the 8 principle components), gender, imaging site, age and total intracranial volume. Many association tests were carried out in this investigation. We corrected for multiple comparisons using the Holm-Bonferroni method [35]. In Step 3, we examined the degree to which the set of brain regions identified by sPLS may act as an intermediary endophenotype between the PRS scores and the impulsivity and BMI phenotypes. In other words, we examined if the brain regions could help explain (or mediate) the observable association between ADHD and BMI genetic vulnerabilities and the impulsivity and BMI phenotypes. The mediation (or indirect) pathways were defined by the product term of the pathways of interest (e.g., PRS to brain BY brain to phenotype). There were four overall possible effects: 1) ADHD PRS → brain regions → impulsivity symptoms; 2) ADHD PRS → brain regions → BMI; 3) BMI PRS →brain regions → BMI; and 4) BMI PRS →brain regions → impulsivity. Because standard errors underlying mediation pathways (i.e., the product terms) are known to be skewed, we bootstrapped all indirect effects 10,000 times with bias corrected (90% and 95%) confidence intervals. The mediation pathways reported here are based on the bootstrapped variability around the product of non-standardized path coefficient estimates (i.e.,

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b). Mediation pathways were programmed in Laavan [36] in the statistical package R [37]. Results Step 1: PRS scores for ADHD and BMI At the time the study was conducted, n = 874 subjects had complete genetic and phenotypic data. The BMI PRS score was significantly associated with BMI (r = 0.23, n = 874, p = 2.2 × 10 −11 FWE corrected) and the PRS score for ADHD was significantly associated with impulsivity symptoms (r = 0.10, n = 874, p = 0.014 FWE corrected). We also note that impulsivity symptoms were associated with BMI (r = 0.10, n = 874, p = 0.014 FWE corrected), and that the PRS scores for ADHD and BMI were significantly cross-correlated (r = 0.17, n = 874, p = 6.5 × 10 −6 , FWE corrected). Of interest, using Steiger's test for dependent correlations [38], we found that the correlation between the PRS scores of ADHD and BMI was higher (p = 0.036 FWE corrected) than the correlation between the phenotypic measures of impulsivity and BMI. Step 2: the shared neural correlates of the PRS scores of ADHD and BMI Of the 874 subjects who had both complete genetic and phenotypic data, 604 had both T 1 and fMRI data that passed QC. Using sPLS, we found that both the ADHD and BMI phenotypes, and their respective polygenic risk scores, are significantly associated with a common neural substrate, constructed from T 1 and fMRI data, which we term the 'neural endophenotype'. The PRS for BMI was associated with

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the neural endophenotype at r = 0.12, n = 604, p = 9.5 × 10 −3 , FWE corrected, whilst the ADHD PRS was significant at r = 0.087, n = 604, p = 0.036 FWE corrected. ADHD and BMI phenotypes were also associated with this set of brain regions, with ADHD associated at r = 0.091, n = 604, p = 0.035 FWE corrected, and BMI associated at r = 0.15, n = 604, p = 9.0 × 10 −4 FWE corrected respectively. These correlations are summarized in a matrix and path diagram in Fig. 1. The neural endophenotype is made up of grey matter regions and regions of activation derived from the MID task. Grey matter regions contributing to this neural endophenotype were located bilaterally in the cerebellum, amygdala, hippocampus, para-hippocampus and orbital frontal cortex, which all present bilaterally. There was also a largely left lateralised grey matter cluster in the inferotemporal cortex. sPLS weights in each of these brain regions were negative, implying an inverse association between PRS scores/phenotypes and grey matter. Neural endophenotype clusters that came up in the MID task were largely left lateralised and included the fusiform gyrus and para-hippocampus, postcentral and parietal inferior, calcarine and occipital superior and frontal superior medial cortex. These results are displayed in Fig. 2. sPLS weights in each of these brain regions were positive, implying a positive association between the MID contrast map and the PRS/ phenotype scores. The full set of VBM and MID clusters identified and localised in the sPLS analysis are

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tabulated in Supplementary Tables S1 and S2. Discussion This study set out to examine if there are shared genetic and neural correlates of the ADHD (impulsivity) and BMI [39] phenotypes. Our results support previous ADHD-related research in showing an association between these two phenotypes [3]. Further analyses showed that the PRS scores for ADHD and BMI were correlated with each other and with grey matter across the brain and contrast maps derived from fMRI scans conducted during the MID task. Importantly, these neuroimaging measures also associated with the phenotypes of impulsivity and BMI. These results extend present knowledge of the biological underpinnings of the association between ADHD and BMI in three main ways. Firstly, using previously established genome-wide evidence, and a multi-modal whole-brain approach, this study showed that the PRS scores and phenotypes of ADHD and BMI simultaneously associated with decreases in grey matter in similar brain areas as reported by the case-control ADHD ENIGMA mega-analysis [7] as well as certain case-control designs of obesity [9]. These areas include the cerebellum, amygdala, hippocampus, orbitofrontal and inferotemporal cortex. The functions of these brain areas underscore the importance of impairments in cognitive and behavioural control and impulsivity in both ADHD and BMI. For example, the fronto-cerebellar networks have been implicated in impairments of cognitive control (e.g., over-riding impulses) in both ADHD and obesity [40,41]; the ability to consider future consequences/adjust behaviours [41]; and the inhibition of eating behaviour [42]. Likewise, the amygdala and hippocampus have been associated with impulsivity symptoms in ADHD [43] as well as weight gain

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and overeating behaviours such as continuing to eat even when sated [44][45][46][47]. Finally, the orbital frontal cortex has been linked to impairments in cognitive and attentional control in ADHD [48], but also potentially to selection and consumption of calorie-rich foods [49] and sensitized reactivity to (foodrelated) reward [50]. The second set of findings relate to the reward anticipation fMRI task. There was an increased BOLD response for the posterior visual and association areas, postcentral, cerebellum and frontal medial cortex. This was consistent with previous findings from both the MID task and other fMRI paradigms used to assess reward processes. With regard to the MID task, our findings converged with previous research that reported abnormalities in frontal-parietal and cerebellar-parietal networks [51,52]. Supporting other reward processing studies, we identified increased BOLD response in the cerebellum and postcentral gyri [47,53], in addition to reward areas in the medial frontal regions [54,55]. Importantly, both the MID-related results and previously mentioned The panel on the right shows correlation values between the different biological and phenotypic measures investigated in this study, the lower triangular matrix shows correlation values between the various biological measures, whilst the upper triangular matrix shows the FWE-corrected significance levels of these associations grey matter results showed abnormalities in visual processing areas (i.e., inferotemporal and association cortices for grey matter and posterior visual and association cortices for the MID task). These abnormalities may be implicated in visual attention biases to reward-related cues (e.g., food or reward) in both obesity and ADHD [37][38][39]. Third, we examined a multivariate mediation model.

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Here, the associations between the ADHD and BMI PRS scores and the impulsivity and BMI phenotypes were partially carried by the brain areas identified by sPLS. We therefore suggest that these brain areas (structural + functional) may act as a neural endophenotype [56] between the genetic liabilities of ADHD and obesity and the manifestation of their (observable) phenotypic association. By definition neurobiological endophenotypes mark genetic vulnerability but are also independent of disease state [57]. Our suggestion of a neural endophenotype is consistent with the idea that a limited number of neural systems may engender risk for a range comorbid psychiatric syndromes [56]. As such, this hypothesized neural endophenotype might extend as vulnerability for known comorbidities of ADHD and BMI, such as substance use and addiction [58] and depression [59,60], to name a few. How might the results of the present study bear on future research? Are there (potential) clinical implications? It is important to note that our findings of genetic influence on ADHD and BMI are non-deterministic and can be context dependent [61]. Indeed, Barcellos et al. [57], taking advantage of a natural experiment, showed that an additional year of compulsory schooling in the UK benefitted individuals with higher genetic risk for obesity, reducing the gap in unhealthy body size in the top and bottom terciles of genetic risk of obesity from 20 to 6 percentage points. This is an interesting result when it is considered that certain interventions targeting ADHD can result in weight reduction and, potentially, viceversa. Although findings are mixed, studies on Methylphenidate

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show that a reduction in ADHD symptoms can associate with decreased BMI, especially for overweight/ obese adolescents [3,62]. Methylphenidate has also been proposed as a treatment for obesity [63,64]. Future research should examine if individuals at high genetic risk for both ADHD and BMI will especially benefit from interventions tailored for one-or both-of these conditions. Our findings should be considered in light of a number of limitations. Firstly, our models were statistically drivenalthough theoretically informed. The models are therefore dependent on the properties of the measures included. While our sPLS model identified simultaneous association between the PRS scores, the two neuroimaging modalities and the phenotypic measurements of ADHD and BMI, this does not mean that this model-or the study variables contained within it-is the best (or only) solution. Secondly, it is also important to note that PRS and neural correlates only explain a small proportion of the liability for many psychiatric difficulties and other traits. Thirdly, the current findings differ from reward anticipation in case-control ADHD designs [65,66] and for clinical remission [67]. Relatedly, it will be of interest to replicate the present results in clinical samples, for ADHD and BMI separately, across different age groups, and across different ethnic groups. Fourth, in the mediation analyses, the ADHD-related pathway had larger bias corrected CIs (90%) compared to the BMI-related pathway (95%). There are at least two reasons for these different CIs. The GWAS discovery sample for ADHD (n = 46,350) is smaller than BMI (n = 339,224), which can affect the relative predictive power of these

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PRS scores [68]. In addition, we examined the ADHD PRS in relation to impulsivity symptoms, which is less precise than examining the BMI PRS in relation to BMI. Conclusion Our results indicate that ADHD and BMI PRS scores are significantly correlated, suggesting shared genetic risk between the traits. In a data-driven model, both the PRS scores were associated with the phenotypic measures of ADHD and BMI, as well as shared neural correlates of impairments in inhibitory control and reward processing. ( Compliance with ethical standards Conflict of interest TB has served as an adviser or consultant for Actelion, Bristol-Myers Squibb, Desitin Arzneimittel, Eli Lilly, Hexal Pharma, Medice, Novartis, Pfizer, Shire, UCB, and Vifor Pharma; he has received conference attendance support, conference support, or speaking fees from Eli Lilly, Janssen McNeil, Medice, Novartis, Shire, and UCB; he has been involved in clinical trials conducted by Eli Lilly, Novartis, Shire, and Vifor Pharma; and he has received royalties from CIP Medien, Hogrefe, Kohlhammer, and Oxford University Press. EDB has received grant support, including Ph.D. support, from General Electric Healthcare; he has served as a consultant for IXICO, and he has received an honorarium for teaching in a scanner programming course run by General Electric Healthcare. ALWB has received funding from the Science Foundation Ireland Stokes Programme (07/SK/B1214a). PG has received a research grant from Lyndra and an honorarium paid to her employer from GlaxoSmithKline. LP has received conference attendance support or speaking fees from Medice, Novartis, and Shire. HW has received a speaking honorarium from Servier. Dr. Buitelaar

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has served as a consultant, advisory board member, or speaker for Eli Lilly, Janssen-Cilag BV, Novartis, Lundbeck, Roche, Servier, and Shire. Dr. Glennon has served as a consultant for Boehringer Ingelheim. The remaining authors declare that they have no conflict of interest. Publisher's note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations. Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the articleʼs Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the articleʼs Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons. org/licenses/by/4.0/.

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Web-assisted assessment of professional behaviour in problem-based learning: more feedback, yet no qualitative improvement? Although other web-based approaches to assessment of professional behaviour have been studied, no publications studying the potential advantages of a web-based instrument versus a classic, paper-based method have been published to date. This study has two research goals: it focuses on the quantity and quality of comments provided by students and their peers (two researchers independently scoring comments as correct and incorrect in relation to five commonly used feedback rules (and resulting in an aggregated score of the five scores) on the one, and on the feasibility, acceptability and perceived usefulness of the two approaches on the other hand (using a survey). The amount of feedback was significantly higher in the web-based group than in the paper based group for all three categories (dealing with work, others and oneself). Regarding the quality of feedback, the aggregated score for each of the three categories was not significantly different between the two groups, neither for the interim, nor for the final assessment. Some, not statistically significant, but nevertheless noteworthy trends were nevertheless noted. Feedback in the web-based group was more often unrelated to observed behaviour for several categories for both the interim and final assessment. Furthermore, most comments relating to the category ‘Dealing with oneself’ consisted of descriptions of a student’s attendance, thereby neglecting other aspects of personal functioning. The survey identified significant differences between the groups for all questionnaire items regarding feasibility, acceptability and perceived usefulness in favour of the paper-based form. The

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use of a web-based instrument for professional behaviour assessment yielded a significantly higher number of comments compared to the traditional paper-based assessment. Unfortunately, the quality of the feedback obtained by the web-based instrument as measured by several generally accepted feedback criteria did not parallel this increase. Introduction Professionalism is becoming increasingly central in undergraduate and postgraduate training, and the herewith associated research results in a vast increase in the number of papers on the topic ( van Mook, de Grave et al. 2009). Tools for assessing professionalism and professional behaviour have been developed to identify, counsel, and remediate the performance of students and trainees demonstrating unacceptable professional behaviour (Papadakis et al. 2005(Papadakis et al. , 2008. Since validated tools are scarce (Cruess et al. 2006), combining currently available instruments has become the current norm (Schuwirth and van der Vleuten 2004; van Mook, Gorter et al. 2009). Self-and peer assessment and direct observation by faculty during regular educational sessions (Singer et al. 1996;Asch et al. 1998;Fowell and Bligh 1998;van der Vleuten and Schuwirth 2005;Cohen 2006) are some of these tools. Self-assessment is defined as personal evaluation of one's professional attributes and abilities against perceived norms (Eva et al. 2004;Eva and Regehr 2005;McKinstry 2007). So far, there is a scarcity of published studies on self-assessment of professionalism (Rees and Shepherd 2005). Given the poor validity of self-assessment in general (Eva and Regehr 2005), it seems ill advised to use self-assessment in isolation without triangulation from other sources. Peer assessment involves assessors with the same level of expertise and

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training and similar hierarchical institutional status. Medical students usually know which of their classmates they would trust to treat their family members, which illustrates the intrinsic potential of peer assessment (Dannefer et al. 2005). However, a recent analysis of instruments for peer assessment of physicians revealed that none met the required standards for instrument development (Evans et al. 2004). Studies addressing peer assessment of professional behaviour of medical students are beginning to appear (Freedman et al. 2000;Arnold et al. 2005;Dannefer et al. 2005;Shue et al. 2005;Lurie, Nofziger et al. 2006a, b). Observation and assessment by faculty using rating scales is another commonly used method of professional behaviour assessment (van Luijk et al. 2000; van Mook, Gorter et al. 2009; van Mook and van Luijk 2010). Prior studies have revealed that such teacher-led sessions are highly dependent on the teacher's attitudes, motivation and instructional skills (van Mook et al. 2007). When teachers' commitment declines, assessment of professional behaviour may become more trivialised. This may misplace emphasis on attendance rather than participation and on completion of tick boxes rather than informative feedback and students' contribution and motivation (van Mook et al. 2007). In an attempt to further improve professional behaviour assessment, the triangulated teacher-led discussion of selfand peer-assessment of professional behaviour using a paper form is the contemporary practice at Maastricht medical school (van Mook and van Luijk 2010). However, digital technologies have come to influence our ways of working and communicating, and created technology driven ways of teaching, learning and assessing (De Leng 2009). Adaptation to some

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of these changes can be useful (De Leng 2009), for example to reduce the time and expense involved in collecting self and peer ratings and facilitate anonymous information gathering and information analysis. In the National Board of Medical Examiners (NBME)' Assessment of Professional Behaviours (APB) program such web-based technology is contemporarily used (Mazor et al. 2007(Mazor et al. , 2008National Board of Medical Examiners 2010). The study presented in this paper investigated the potential advantages of a web-based instrument versus a 'classic', paper-based method to assess professional behaviour in tutorial groups in a problem-based curriculum. In a comparison of these two approaches we focused on: 1. The quantity and quality of comments provided by students and the feedback provided by their tutor and peers, and on 2. The feasibility, acceptability and perceived usefulness of the two approaches. Methods and research tools The study involved all medical students enrolled in the second, ten-week course in year 2 at the Faculty of Health, Medicine and Life Sciences, Maastricht University, the Netherlands. During the bachelor programme of the six-year problem-based medical curriculum, professional behaviour is assessed on various occasions in tutorial groups during all regular courses (van Mook and van Luijk 2010). Each tutorial group consists of ten students on average and a tutor/facilitator, and each meeting lasts 2 h. For the purpose of this study, the students were divided into two groups: those in tutorial groups with even numbers and those in groups with odd numbers. The first group used a web-based instrument to assess professional behaviour and

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the other group used the usual method with a paper assessment form. We will first describe the two assessment methods in some detail. The 'classic' paper-based professional behaviour assessment form The working group Consilium Abeundi of the Association of Universities in the Netherlands, proposed a practical definition of professional behaviour (Project Team Consilium Abeundi van Luijk 2005;van Luijk et al. 2010; van Mook and van Luijk 2010). They framed professionalism as observable behaviours, reflecting the norms and values of the medical professional. Three categories of professional behaviour were distinguished: 'Dealing with work and tasks', 'Dealing with others', and 'Dealing with self-functioning' (van Luijk et al. 2000;Project Team Consilium Abeundi van Luijk 2005). These categories, together with the related clarifying descriptions, are the basis of the professional behaviour assessment form that is in use at Maastricht medical school since 2002 ( Fig. 1) van Luijk 2009, 2010). Early in the curriculum students are familiarised with its use. Professional behaviour is assessed at the start, halfway through and at the end of each regular course. For the halfway assessment each student prepares a self-reflective assessment and enters it in the form using the clarifying descriptions as a reminder and starting point. In the subsequent plenary session of the tutorial group, chaired by the tutor, the professional behaviour of each student is assessed by the group. All group members (students and tutor) are required to contribute to the discussion. All the comments and feedback are documented on each student's form by the tutor. At the end of the course

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this process is repeated, followed by a final summative assessment, resulting in a pass or fail (van Mook and van Luijk 2010). The web-based instrument The web-based instrument is based on an application that consists of a 360°feedback system specifically designed for higher education. Its development involved more than thirty pilot studies and evaluations by over 6,000 students. Prior to the current study, the tool was piloted at Maastricht in a group of first year students, which did not participate in the current study. Providing adequate practical information to students and tutors prior to using the application and rephrasing of items to achieve a more detailed focus on aspects of professional behaviour were considered prerequisite for the successful implementation of web-based assessment (unpublished data). The web-based instrument used for assessment of professional behaviour pertained to the same three categories (and clarifying descriptions) also used on the paper form (Project Team Consilium Abeundi van Luijk 2005). Ample information about background, confidentiality, timing and some practical matters was made available to students and staff electronically and in writing prior to, and during Assessment form for professional behaviour in tutorial groups in years 1-3, academic year ……………………………….. Only required for END OF BLOCK ASSESSMENT: Signature of the student (indicating that the student has read the completed form): Signature of the tutor: Dealing with work* Preliminary/interim assessment Final assessment Areas requiring the student's attention: PRELIMINARY/INTERIM ASSESSMENT: unsatisfactory satisfactory reliable assessment not possible due to frequent nonattendance of the student FINAL ASSESSMENT: unsatisfactory satisfactory reliable assessment not possible due to frequent

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nonattendance of the student Requires attention: The areas referred to in the comments are in need of attention and improvement. Satisfactory: The student is functioning adequately within the present circumstances. * Details and explanations of the categories are provided on the back of the form. Unsatisfactory: below the expected average level of functioning in the tutorial group, clear areas of weakness where more work and improvement are required have been identified. Satisfactory: expected or higher level of functioning in the tutorial group, although areas where more work and improvement are required may be present. Cannot be assessed: reliable assessment is not possible because the student has frequently failed to attend group sessions. Tutor: If final assessment is UNSATISFACTORY OR ASSESSMENT NOT POSSIBLE, please send 1st copy to Secretary of the Committee of Professional Behaviour, Department of Educational Development and Research, UNS 60, Room N4.13 Student: one copy should be inserted in the PORTFOLIO one copy should be kept by the student for his/her own records Fig. 1 The paper form used for professional behaviour evaluation and assessment at the Faculty of Health, Medicine and Life Sciences, Maastricht University, The Netherlands the opening session of the course, as well as verbally to the tutors during the tutor instruction session. Halfway and at the end of the course each student in the web-based assessment group received an internet link in an e-mail. Clicking the link gave access to the web-based assessment instrument. The students were asked to complete the questions themselves and then invite five peers and the

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tutor of their group to evaluate their professional behaviour and provide feedback. Selection of the peer students was standardised to the five students listed immediately below the student's name on the centrally randomly generated list of the tutorial group members, resulting in a semi-anonymised feedback procedure. Ample space for narrative feedback relating to the three categories of professional behaviour was provided for each questionnaire item (Fig. 1). All items were also answered using a Likert scale (1 = almost never to 5 = almost always). The students received the results of the feedback process in the form of a printable report presenting the results of their self-assessment relative to the assessment by their peers as well as an overview of all the narrative comments. The web-based group used the printed reports and the paper-based group used the completed paper-based forms to discuss each student's professional behaviour during the end-of-course assessment in the final tutorial group of the course. End-of-course questionnaire At the end of the last tutorial group of the course, all students of the two groups were asked to complete a questionnaire addressing fourteen aspects of feasibility, acceptability and perceived usefulness of the two instruments. The tutors were invited to report their findings by e-mail. All data were recorded and analysed anonymously. Analysis All narrative comments were independently coded and analysed by two blinded researchers (WvM and SG). Units of comments consisting of one grammatical clause but covering different topics were considered to be different units of comments. They used five generally accepted feedback rules

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to label the units of comments as incorrect or correct feedback (Table 1) (Pendleton and Schofield 1984;Branch and Paranjape 2002). Since feedback should preferably meet as many criteria as possible, an aggregated score across all five feedback categories was constructed (total scores of 0-3 were considered unsatisfactory and requiring improvement; total scores of 4 and 5 were considered satisfactory). The researchers (WvM and SG) discussed any discrepancies in their coding until agreement was reached. The number and nature of the comments from the interim and final evaluations were compared between the web-based (intervention) group, and the paper-based (control) where r paper is the standard deviation in the paper-based group. ES % 0.30 was considered a small effect of negligible practical importance; ES % 0.50 was considered a medium effect of moderate practical importance, and ES % 0.80 large effect of considerable practical importance (Cohen 1987;Hojat and Xu 2004). Results Of the 307 (198 females, 109 males) medical students enrolled in the second course of the second year, 150 were assigned to tutorial groups with even numbers (web-based group) and 157 to the tutorial groups with odd numbers (paper-based group). Since assessment of professional behaviour is mandatory, the participation rate was 100%. We will first present the results of the quantitative and qualitative analyses of the narrative feedback provided at the interim and final assessment of professional behaviour in the two groups. After that we present the results for the feasibility, acceptability and perceived usefulness of the two assessment instruments. Analysis of the amount of feedback The

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total numbers of comments per category of professional behaviour for the interim and the final assessments are presented for the web-based and the paper-based group (Table 2). In the web-based group a mean of 4.5 invitations to peers to provide feedback were sent by each student (standard deviation 3). The number of comments was significantly higher in this group than in the paper-based group for all three categories (dealing with work, others and oneself). However, at the final assessment the total number of comments relating to the category 'Dealing with oneself' had halved compared to the interim assessment and this decrease was mainly attributable to a marked decrease in the comments provided by the web-based group. Analysis of the quality of the feedback The results for the quality of feedback at the interim and the final assessments are presented for the categories of professional behaviour (dealing with work, others and oneself) as correct and incorrect in relation to the aggregated score on the five feedback rules ( Table 3). The inter-rater agreement during primary coding was 15834 out of 16165 codes (97.9%) for 3233 comments (Kappa = 0.87). When statistical significance was corrected for sample size no difference in the aggregated scores on all five feedback categories was found. Several differences of potential practical significance pertaining to the five generally accepted feedback rules were however, found, all favouring paper-based assessment. The feedback in the webbased group pertaining to the categories 'Dealing with others' and 'Dealing with oneself' was for example more often unrelated to observed behaviour.

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However, in the view of the statistical 'multiple comparisons' problem, the statistical significance regarding the between-groups differences revealed by these individual analysis is questionable. Finally, the majority of comments relating to the category 'Dealing with oneself' consisted of descriptions of a student's attendance to the neglect of other aspects of personal functioning. Feasibility, acceptability and perceived usefulness The response to the questionnaire was 96% (143/157) in the paper-based group and 81% (121/150) in the 'web-based' group. Table 4 shows the mean scores per questionnaire item for the two groups. The differences between the groups were significant for all items and in favour of the paper-based form. The paper-based group yielded fourteen student comments on the use of the paper form. Nine comments emphasised the usefulness of the form, four offered suggestions for minor adaptations and one stated that the form was time consuming. The tutors did not comment on this form. The students in the web-based groups provided 179 comments (Table 5) and the tutors provided fifteen comments. The tutors emphasised the absence of interpersonal contact and the necessity of face-to-face contact during assessment of professional behaviour. They also thought that the web-based instrument was time consuming and they reported some technical problems (e.g. printing). Discussion Although other web-based approaches to assessment of professional behaviours have been studied (Mazor et al. 2007(Mazor et al. , 2008Stark et al. 2008) as well as are contemporarily used(-National Board of Medical Examiners 2010), very few studies specifically address the amount and quality of feedback resulting from using such approach.

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The assessment method that is currently used at Maastricht medical school requires each student to reflect on their professional behaviour and requires all members of a tutorial group (tutor and students) to provide feedback on the professional behaviour of each student, which is then recorded by the tutor on the assessment form. This process was deliberately mimicked in the web-based instrument, which elicited feedback from students and tutor on the same three categories and items relating to professional behaviour that are included in the paper form. The study reveals that the number of comments was significantly higher in the webbased group compared with the paper-based group. The quality of the feedback, however, did not parallel the quantitative increase. When considering the aggregated scores on the five feedback criteria no differences in quality of feedback was found between the groups (Table 3). Nevertheless, the feedback provided by the web-based group showed poorer quality in relation to several feedback criteria (e.g. was unrelated to the observed behaviour; data not shown). However, as previously mentioned, the statistical significance revealed by these individual analysis is questionable. Moreover, the survey results on acceptability, feasibility and usefulness of the instruments were strongly in favour of the paper form. It should be noted that this result might be partly due to technical difficulties that were experienced with the web-based instrument despite adequate technical preparation and extensive tutor and student instruction. However, even when these limitations are taken into account, the web-based instrument did not show an improvement in educational impact compared with the

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existing method of assessing professional behaviour. Another striking finding, which is unrelated to the nature of the assessment instrument, was the emphasis on attendance in the feedback relating to the category 'Dealing with oneself' and the relative absence of feedback on other aspects of self-functioning. An earlier analysis of 4 years of experience at Maastricht with paper-based assessment of professional behaviour had yielded similar findings (van Mook and van Luijk 2010). This suggests that the context (small group sessions) in the earlier years of medical school may be less suited to stimulate self-reflection (van Mook and van Luijk 2010). Perhaps attendance and time management as measures of responsible behaviour should be evaluated separately from feedback on other aspects of professional behaviour, a suggestion that was also put forward during the plenary discussion at a recent symposium on van Mook and van Luijk 2010). Comparison of the results of this study to results reported in the literature is difficult since few studies on web-based instruments to assess professional behaviour have been published. However, there are some published reports on the development and use of webbased assessment in general (Wheeler et al. 2003;Tabuenca et al. 2007). In one study, implementation of a web-based instrument resulted in a substantial reduction in administration and bureaucracy for course organisers and proved to be a valuable research tool, while students and teachers were overwhelmingly in favour of the new course structure (Wheeler et al. 2003). Another study described a successful multi-institutional validation of a web-based core competency assessment system in surgery (Tabuenca

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et al. 2007). However, the transferability of these more general studies to web-based self-and peerassessment of professional behaviour seems limited. Studies addressing the NMBE's APB program however, report comparable promising results, with improved faculty comfort and self-assessed skill in giving feedback about professionalism as an example (Stark et al. 2008). It seems therefore advisable to conduct further studies to examine the effectiveness and optimal use of web-based assessment of professional behaviour. Although the literature pertaining to web-based assessment is sparse, the peer assessment literature provides evidence of the importance of anonymity, or at least confidentiality, for the acceptance of peer assessment Shue et al. 2005). That is why we used a semi-anonymous feedback procedure in the web-based assessment in this study. Although reliability can be enhanced by increasing the number of raters (Ramsey et al. 1993;Dannefer et al. 2005), the desired number of raters may not be feasible or acceptable, for example due to time constraints. Consequently, in the current study we limited the number of peer raters to five randomly selected students (Ramsey et al. 1993;Dannefer et al. 2005). It seems reasonable for medical schools to base the selection of peer raters on practical and logistical considerations (Arnold et al. 1981;Arnold and Stern 2006;Lurie, Nofziger et al. 2006a, b), since bias due to rater selection has been shown not to affect peer assessment results (Lurie, Nofziger et al. 2006a, b). Although some anticipated problems could thus be adequately addressed, mention must be made of some remaining limitations of the current study. Problems with report, such

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as print problems and the presentation of results 10 10 Process of professional behaviour evaluation becomes less personal, more distant 7 Study limitations In the preparation phase we were confronted with limited availability of tools for webbased multisource feedback. Because re-designing an existing tool proved costly, a for the purpose of this study superfluous feature, (the Likert scales), was left unchanged, and this may have unavoidably influenced the results, for instance those relating to time investment. The content of the web-assisted and paper versions of the instrument was otherwise identical. Furthermore, it cannot be excluded that the results were negatively affected by the participants' unfamiliarity with web-based assessment instruments, even though the implementation process was carefully prepared based on feedback from a pilot study. Ample time was spent on technical preparation and the participants received information and instruction on multiple occasions. Furthermore, the possibility of omitting redundant comments and concretizing comments before noting them by the tutor, or the more limited space may have contributed to the lower number and/or the higher quality of the comments in the paper based group. Finally, automated data extraction only enabled feedback analysis at the level of the whole year group, although analysis of data at individual (students, tutors) or tutorial group level would have been preferable. Conclusions The results revealed that a confidential web-based assessment instrument for professional behaviour yielded a significantly higher number of comments compared to the traditional paper-based assessment. The quality of the feedback obtained by the webbased instrument was comparable as measured by several generally

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accepted feedback criteria. However, judging by the questionnaire results students strongly favoured the use of the traditional paper-based method. The interpersonal nature of professional behaviour prompted comments that professional behaviour was eminently suitable for 'en-groupe', face-to-face discussion and assessment. Although teachers and students are nowadays preferably 'wired for learning' it seems that, so far, professional behaviour assessment does not necessarily require the use of advanced assessment technologies, although such new 'innovative' electronic and/or web-based assessment methods thus do result in more feedback of comparable quality. Their exact position among the currently used, labour-intensive traditional assessment armamentarium needs to be subject of further study.

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Walking with light and the discontinuous experience of urban change This paper is concerned with the affective power of light, darkness, and illumination and their role in exposing and obscuring processes of rapid urban change. Little academic attention has focused on how lighting informs multiple, overlapping, and intersecting urban temporalities and mediates our experience of an ever ‐ changing city. This paper foregrounds a walk through the illuminated city at night as an epistemic opportunity to develop an embodied account of material and temporal change in ways that disrupt the aesthetic organisation of the sensible world at night. By detailing the discontinuous experience of walking through differently lit spaces, the paper develops novel ways of conceptualising the experience of urban change that unsettle common understandings of subjectivity, temporality, and the city. The paper draws on a single night's walk from Canning Town to Canary Wharf in east London – an area that has recently undergone rapid change, including the erection of enclaves of high ‐ rise development. By accentuating the shared experiences of walking with light, we reveal the affective capacities of light and dark to conceal and expose wider material, embodied, and temporal urban changes but also how we might challenge the organisation of the nocturnal field of the sensible. At night, a plethora of competing light sources reveal how successive waves of urban change and infrastructural upgrades have been introduced (Cubitt, 2013;Jakle, 2001;Otter, 2008). Recently, geographers have warned of the potentially homogenising and sensorially sterilising effects of contemporary lighting practices (Edensor & Millington, 2018)

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and shown how such effects can be ameliorated throughout the design process (Ebbensgaard, 2019b). Scholars have also discussed moral and aesthetic landscapes of darkness and illumination (Dunnett, 2015;Edensor, 2012;Edensor & Millington, 2009) and explored how residents make sense of changes in lighting, as with the widespread introduction of LEDs (Ebbensgaard, 2019a;Pink & Sumartojo, 2017). This paper expands such concerns by investigating how urban lightscapes mediate our experiences of urban change and manifest different forms of power. Yet by foregrounding the discontinuities experienced while walking through differently lit spaces, we unsettle notions that urban illumination is bound within discrete spaces and times. In seeking to articulate more diverse accounts of the experience of urban change, we foreground the night walk as a method for disrupting dominant forms of aesthetic nocturnal organisation through disclosing embodied, affective experiences of lightscapes. Our walk takes us from Canning Town in the borough of Newham to Canary Wharf in the neighbouring borough of Tower Hamlets, through an area of great ethnic diversity generated by successive waves of migration over two centuries. This former heartland of empire on the north bank of the River Thames was once lined with docks named after their connections with colonial destinations. Replete with swathes of dense, working-class housing, markets, power stations, and factories, the area has been transformed by post-war public housing developments that gradually filled in extensive areas of bomb damage and, subsequently, by vast regeneration projects initiated in the 1980s. In tandem with this process of discontinuous urban renewal, the area has been illuminated in

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piecemeal fashion by a host of agentslocal authorities, Transport for London, independent housing associations, and private landownerswith little attention to coordination. According to lighting designer Mark Major (2015, p. 153), London's incongruous illumination and the lack of borough and city-wide coordination have "broken" the city's architectural hierarchy and "diminished" its experiential qualities. Without a concerted lighting strategy for the city, in 2020 current Mayor Sadiq Khan commissioned the think tank Centre for London to scrutinise London's lighting and to inform future Mayoral and borough policies. Similarly, flagship projects like the Illuminated River (n.d.), which illuminates 14 bridges along the city's River Thames, exemplifies attempts to achieve greater coordination in London's illumination. Yet currently the city is undergoing an unprecedented period of privately funded, high-rise development that is further diversifying the night time environment in new ways: Of the 541 towers above 20 stories that were planned in 2018, 45% are located in east London and 20% in Tower Hamlets alone, joining London's first consolidated cluster of "iconic" high-rise buildings on Canary Wharf. On our walk, we pass through areas where recent massive, mixed-use, high-rise developments are bringing dramatic transformation. Geographers argue that the surge in financialised forms of private territorialisation (Appert & Montes, 2015;Kaika, 2010) are turning parts of London into archipelagos of secluded, luxury enclaves (Atkinson, 2016;Graham, 2015). Across social and public media, these developments have received further critical attention, not for their obtrusive presence on the nocturnal skyline but paradoxically for their invisibility. Shrouded in darkness, residential towers appear with what Graham terms "dead

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windows" (2015, p. 633), prompting critics to question the wider impacts of these "'zombie' estates of absentees" (Jenkins, 2017, n.p.). Here, light and darkness emerge as powerful agencies in mediating urban change, exposing socio-economic inequality. By drawing critical attention to how urban lighting bestows regularity, aesthetic conformity, and selectivity in these development schemes, we follow Rancière's (2009) approach to regimes of the sensible in questioning lighting's role in distributing the visible and invisible in ways that come to appear as "natural." By walking across developments lit according to different schemes and also experiencing illumination outside these schemes, we foreground both how power is manifest through lighting and the discontinuities of the changing city. Critically, we suggest that neither nocturnal design nor the ways in which we inhabit it are wholly determined by dominant aesthetics of urban regeneration. In developing a critical framework for conceptualising how light and darkness mediate the experience of urban change, we situate the study within key geographical debates about urban illumination and power, the night-time, and walking. Subsequently, we describe and reflect on different sequential stages of our nocturnal journey through a succession of vignettes, drawing on auto-ethnographic and dialogical accounts of walking together. By foregrounding our embodied experiences of moving through the changing landscape, we argue that walking with light challenges the dominant organisation of the nocturnal field of the sensible. advertisers, state authorities, place-makers, civic bodies, and bureaucrats have sought to produce nocturnal urban environments that attract, control, and organise inhabitants. First, lighting practices create "new centres of power and

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new margins of exclusion" (Koslofsky, 2011, p. 280), wherein certain areas and buildings are conspicuously illuminated whereas others are shrouded in gloom. Political authority, corporate presence, and class status can clearly be traced in the organisation of lighting across the urban nightscape, signifying the unequal distribution of financial, social, and political power. Especially overt expressions of power stage nocturnal spectacles, as with the notorious Nazi rallies at Nuremberg for which Albert Speer designed "cathedrals of light" that evoked immense classical columns fashioned by 130 giant searchlights. In London, however, light was introduced gradually, in piecemeal fashion, producing a geography in which artificial illumination became "a symbol and a determinant of urban differentiation" (Otter, 2008, p. 335). New regimes of spatial ordering implemented a calculated invisibility, illuminating that which was esteemed but consigning to darkness features and districts conceived as less deserving of visual attention. State institutions, heritage buildings, monuments, and wealthy areas continue to be highlighted against the contrastingly dark backcloth of less venerated realms, inscribing particular identities and values on urban space. In marking wealth and power, such topographies have inscribed massive distinctions between different realms of class and race, as in 19th-century American cities (Baldwin, 2004). In contemporary times, while a selective aesthetic ordering persists in the glaring illumination of high-rise corporate buildings and iconic structures, the nocturnal design of upmarket residential buildings is increasingly embracing darkness and softer, integrated, and indirect illumination (Ebbensgaard, 2019b). Such crepuscular designs contrast with the city's "rougher" quarters, with the harsh floodlighting and poorer quality lighting of lowlier

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housing estates (Sloane, 2016). While, as Nye suggests, light and darkness historically expose the competition "between public and private lighting, and between collective and individualistic visions of the urban night landscape" (2015, p. 31), recent changes in lighting design complicate these established binaries. Large parts of London's "public" lightingstreet lighting, traffic lights, the illumination of public housingare managed by private consultants through private finance initiatives (PFIs). As the marginalisation of local expertise diminishes the capacities of local authorities to shape the night, the recent Mayoral initiative cited above with Centre for London seems welcome if somewhat cosmetic. On our walk through a range of developments across east London, we explore how the shifting terrains of aesthetic organisation are reshaping the attentional orientation of our senses. Second, and relatedly, lighting is commonly deployed to competitively assert status by aestheticising individual homes and neighbourhoods, manifesting cultural capital through the expression of "good taste." Both domestic and commercial illumination have become swept up in taste-making strategies, practices entangled with intensified consumption and lifestyle promotion, and are reconfiguring class identities. Light is increasingly adopted in design-led regeneration, where serialised "designscapes"an agglomeration of "brand design, architecture, urban planning, events and exhibitions"articulate shared tastes, motivations and connections to produce "aesthetic consent" (Julier, 2005, p. 874). Such illuminated expressions of distinction commonly vilify older technologies and vernacular styles as outmoded or lacking taste (Edensor & Millington, 2009). These recent trends to impose serialised lighting echo the ethos of outsourcing expertise through PFI contracting and technocratic solutions to uniform application. Yet while the promise

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of a "technological fix" has been central in driving the replacement of sodium vapour lighting with LEDs (Bille, 2019;Ebbensgaard, 2019a), as we emphasise, London's lightscape is currently typified by multiplicity and discontinuity in which no wholly dominant approach to light design prevails, and our nocturnal walk seeks to experience these divergent regimes and styles. Third, illumination has long been deployed to control movement and presence in nocturnal space. In Victorian London, Otter (2008) discusses how illumination belonged to an array of technological applications that drastically enhanced urban safety, mobility, and health as part of a moral, political, and sensory bourgeois refashioning of the city. This biopolitical reordering normalised surveillance practices and technologies, making the disciplining and policing of social order operate more directly through the site of bodily perception. Such technological applications have been extended, with searchlights used to regulate bodies in dark spaces, domestic and industrial security lighting widespread, and bright lighting deployed to render images recorded by CCTV legally admissible. Nonetheless, as Williams declares, darkness provides a cloak for alternative and oppositional practices that contest these ordering impulses: "[B]ecause of its transgressive meanings and societally harmful uses, darkness threatens to deterritorialize the rationalizing order of society … when it obscures, obstructs, or otherwise hinders the deployment of the strategies, techniques, and technologies" of regulation (2008, p. 518). The nighttime city thus remains subject to a shifting spatial politics wherein certain spaces are contingently commodified, regulated, contested, claimed, and abandoned by different parties. Fourth, Otter's (2008) observation that the reconfiguration of Victorian London's nightscape was

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concerned with ordering the senses prefigures how lighting has become integral to producing, perceiving and sensing bodies. This importantly foregrounds how a politics of light must therefore, as Rancière suggests, revolve "around what is seen and what can be said about it, around who has the ability to see and the talent to speak, around the properties of spaces and the possibilities of time" (2009, p. 13). Lighting is a key element in how the sensible is distributed through "the configuration of a specific space, the framing of a particular sphere of experience, of objects posited as common" (Rancière, 2009, p. 24). Lighting orchestrates what is seen and unseen, which things and places glow, and which styles of illumination are prevalent. Existing before we enter space and without our participation in their design or installation, illumination influences how we become habituated to nocturnal space, unreflexively performing sensory and practical habits. Tolia-Kelly insists that "the sphere of the senses is not a reified sphere that operates beyond the economic or political" for "aesthetic practices are coopted into the expressive infrastructure" (2019, p. 137). Importantly, she contends that such practices instantiate structures of feeling that are "sanctioned, reproduced and maintained" (2019, p. 127). Relatedly, Hudson argues that our sensual realm has become entangled with "the material life of capital" (2020, p. 2) in ways that obscure its mode of operation. The senses are also imbricated in how illumination expresses the spatial inequality, stylistic claims of distinction, surveillant technologies, and standardisation discussed above. Yet this is not to infer

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that dominant regimes of sensibility invariably prevail, for possibilities for revealing the power behind sensory arrangements and offering alternative modes of organisation and new bodily capacities through what Rancière calls "dissensus" may emerge (Kullman, 2019). Political and creative acts of dissensus by subaltern, oppositional, and radical groupsfor instance, light artists, guerrilla light groups, and social lighting designers (Edensor, 2017)create possibilities for producing "new taxonomies, paradigms, and palettes of sensibilities" (Tolia-Kelly, 2019, p. 124). In addition, dissensus may emerge in encounters with outmoded or unorthodox designs, or by involuntary memories triggered by unanticipated sensations. This underlines how the impacts of lighting do not merely accord with those intended by designers but are configured by people into their everyday lives, their tastes, memories, and predilections to shape apprehension and interpretation. This is especially salient for light, which is always more than symbolic and representational, for illuminations "radiate presence, projecting their qualities outwards and colouring the environs, seeping into neighbouring spaces, colouring and shedding light on surfaces, bodies and things, mixing with other lights and being reflected in clouds, water and glass" (Thibaud, 2011, p. 211). Light's powerful propensity to tincture surroundings provokes affective and emotional resonances in the sensing body, activating passions, instigating sensual pleasures and discomforts, and attuning us to the tone of place (Bille, 2017). In exploring a sensory politics of light, we seek to understand how our bodies register the changes in the urban nightscape through which we walk, exploring how forms of light might redistribute our sensory and affective capacities, as we now detail.

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| WALKING… As we move through the nocturnal city, our perceptive registers constantly adjust to shifting, contrasting, and overlapping lighting regimes and the insurgent contingencies of temporary and transient illuminations. The analytical attention we pay to these transitory moments is inspired by Rancière's (2009) aforementioned notion of dissensus: the gap that appears in the existing power relations that orient us towards moments "when politics appears and disappears again" (Kullman, 2019, p. 285). The night walk, we argue, holds the promise of attuning our senses to disturbances in the consensual distribution of the sensible, for walking is an embodied engagement through which attention is drawn to distinctive affordances -"the textures, forms and materials that combine and make up the urban landscapes in which we participate" (Hunter, 2017, p. 30). As Benediktsson and Lund contend, "the lives of human beings are tangled up with the temporalities of constantly unfolding landscapes, in a never-ending journey" (2010, p. 6). Walking also exemplifies how much of our experience is "configured ongoingly" (Sumartojo & Pink, 2018, p. 129). As Wylie contends, affective and sensory experiences change in response to the "shifting mood, tenor, colour or intensity of place and situation" (2005, p. 236) as the walker continuously makes connections with and away from the landscape (Lund, 2012). This aligns with Ingold's assertion that humans "make their way through a world-in-formation rather than across its pre-formed surface" (2007, p. 32). While place and subjectivity are constantly unfolding in relation, our capacities to negotiate these changing percepts are continuously made and remade. Accordingly, we

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explore how walking methods may "capitalise on the environment as a prompt to discussion" (Macpherson, 2016, p. 426), following Brigstocke and Noorani's foregrounding of attunement, to explore how "[t]o attune is to tune in or to tune out; it is to calibrate our bodies as instruments" (2016, p. 2). Yet an "invitation to attune" designates a situation that will often be punctuated by "moments when … we resist, ignore or undermine [the invitation]" (Sumartojo & Pink, 2018, p. 121). For this depends on our capacities, desires, and willingness to "go along" or not, suggesting that attentional forms of orientation are not only highly subjective and unpredictable but also subtly chart amorphous and indistinct boundaries of sensory inclusion and exclusion. Accordingly, we recognise the dangers of reproducing universalist accounts of experience that reduce bodies to a singular plane. The diverse and situated understandings of our experience of light and walking are shaped by the historical and socio-cultural conditions that reminds us how "through their racialized, gendered and sexualized markedness, [bodies] magnetize various capacities for being affected" (Tolia-Kelly, 2006, p. 215). Recognising how experiences at night are scripted through gendered (Valentine, 1989), cultured (Bille, 2019), classed (Edensor & Millington, 2009), sexualised (Williams, 2008), and racialised (Henery, 2019) differences, we acknowledge the limitations of our night walk as a method. For instance, as we will describe, we walked beneath an underpass, alongside a busy road, and in areas of minimal lighting, but were not unduly concerned with safety and encountered no threatening or physically discomforting episodes. Others may have

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experienced the walk very differently, emotionally and physically, and in terms of that to which they attended or became attuned. We do not wish to elevate our subjective experiences to a universal truth; rather, we seek to ground the often-abstract discussion of how urban change shapes experience through our embodied, personalised, and dialogical accounts (Lewis, 2017). Often, our cultural differences (one Danish, the other British) emerged through discussions of our immediate aesthetic judgements towards the transitions between bounded lighting schemes, providing an opportunity to situate our discussions about site-specific lighting in relation to wider socio-cultural concerns and our own prior extensive studies that have attuned us to attend to lighting. By paying attention to the edges of these schemes, we tried to discern how regimes of sensibility were established through dominant lighting schemes within bounded sites and where they blended or clashed with other forms of lighting we sought out gaps or "disruptions to dominant orders" (Kullman, 2019, p. 287). Finally, the continuous movement of our night walk provided a method for "grounding" the abstract experience of urban change and the bedazzling experience of rapid verticalisation. As Brown suggests, horizontal movement through the city's skyscrapers symbolically "reengraves the city's grid with [our] physical bodies" (2017, p. 137) offering the potential for sensing otherwise and "[re]writing a relation to modern architecture by way of [our] urban navigation" (2017, p. 156). Our walk modestly seeks to rewrite our relation to the vertical emblems of urban change through partial, personalised accounts of how light and darkness mediated our experiences

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of movement and mobility across east London. | … AND TALKING Acknowledging that there are many ways to walkambling, cruising, or purposefully striding -Hickey et al. envisage how "walking affords a shared sense of the experience of being together in place, played-out as this is through the shared … traversal of the terrain of the field, and traversal of the terrain of experience" (2018, p. 40). Walking together was therefore critical in registering our shifting sensory, affective, and intellectual responses to the lit environments we encountered and reflecting on the dominant regimes of the sensible. While most "academic" walking is either undertaken by the solitary walker (Wylie, 2005) or with researcher participants (Degen et al., 2008), we consider that by walking together we could focus more acutely on the urban nocturnal landscape. We came together to register our impressions when lights solicited our curiosity, pleasure, or repulsion in episodes of thinking-together along the route and to take photographs of the scene under discussion (Sumartojo et al., 2019). Conversation was thus an integral part of our journey, emerging in response to the light we encountered, and initiating "thick descriptions" of the qualities of different illuminated spaces that extended beyond the walk, as we shared ideas and impressions in pubs and from our offices and homes via email. The dialogical method of talking in and ex situ encouraged reflection on the significance of our experiences in exploring how light and darkness mediates experiences of urban change. | The Canning Town underpass On exiting Canning Town tube station, we

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are confronted by high-rise developments comprising mixed-tenure housing, shops, and a hotel. We stand before the once dominant concrete structure, the A13 flyover, now diminished by the lofty towers of Rathbone Market to its north (delivering 652 homes of mixed tenure) and the Hallsville Quarter to its south (delivering 1,100 mixed tenure homes). The sodium vapour lights that (still) extend along the elevated road are outshone by more recent lighting surrounding the massive vertical structures that reflects in their polished stone, brushed steel, and glass surfaces. Walking through Canning Town requires navigation through diverse built forms; it feels like a place littered with residues from years of planning "from above." From the large post-war redevelopments of bomb sites and deteriorating terraced housing to modernist architectural schemes and traffic planning projects, successive waves of urban redevelopment have shaped the area in seemingly conflictual ways. After the London Thames Gateway Development Corporation and the arrival of the Docklands Light Railway spurred redevelopment in the 1980s and 1990s, preparation for the London 2012 Olympics provided the impetus for large-scale master-planned regeneration. A team of architects and landscape architects were commissioned "to create a more pleasant environment for pedestrians and other road users" (London Thames Gateway Development Corporation, 2009, p. 4) and facilitate easier movement for pedestrians "faced by cul-de-sacs, dead ends and a confusing street layout" (London Borough of Newham, 2007, p. 4). The space underneath the A13 flyover was identified as a key site to connect the various stages of the development. The Council opened up the underpass

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as a key route for pedestrians and commissioned artistic events to "animate" the space. Event makers "The Brick Box" proposed an eight-week-long festival underneath the flyover and a one-night lighting festival, "Light Night Canning Town," to "entertain and illuminate, inspire and celebrate" (The Brick Box, 2013). Both projects ran from 2013 to 2015, and were enthusiastically welcomed by local residents, who commended the possibilities for socialising that had otherwise been scarce in a neighbourhood characterised by pub closures. Subsequently, the council commissioned lighting designers to develop a permanent design for the underpass to deliver a public realm that would attract residents by day and night. When we entered the underpass, we were startled by the contrast with the lightscape of the surrounding area, immediately concurring that this illuminated space felt warm and inclusive, with stimulating visual elements. Designed in 2018 by social lighting group, "Light Follows Behaviour," linked to the socially conscious design collective "Social Light Movement" (Edensor, 2017), extensive local consultation informed the transformation of the forbidding environment into a multi-functional space that encourages people to linger, play, sit, and meet. Christened "Terry Spinks Place" after renowned local boxer, the hard textures of the brutalist pillars and ceiling have been softened by embedding LEDs into the concrete floor. They continuously change colour, radiating a soft glow on the concrete ceiling above, toning the ambience of the underpass and fostering a renewed appreciation of its brutalist geometric elements. As we walk amid these playful lights, we linger among different people dispersed throughout the underpass's darker and

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more illuminated passages, socialising in small groups. Through an extensive period of experimentation, light art and design have enabled a local public realm to slowly emerge that transcends the commercial, security, or engineering imperatives that so often dominate design principles in public and pseudo-public spaces. Moreover, the public engagement process exemplifies how negotiation over the meanings of space has the potential to challenge normative understandings of design (Ebbensgaard, 2015) an approach that dramatically contrasts with the illuminated realms that we subsequently walked through (Figure 1). | Invisible cranes Leaving the underpass, we look south down Silvertown Way, our attention suddenly subsumed by a ribbon of red lights hanging high above the ground. After brief bewilderment, we realise that they are situated to alert incoming aircraft to nearby London City Airport to the presence of construction cranes; they also caution pedestrians below of the gradual but relentless redevelopment of the area. In many cities, cranes have become a spectacular ingredient of the nightscape, illuminated in various colours to bequeath a heightened appreciation of their sculptural beauty while affectively broadcasting an image of dynamism and regeneration. Here, though, they are cloaked in darkness, the invisible cranes making the darkened space in between lights and ground feel somewhat uncanny; a seeming empty realm but one colonised by an overarching power. Indeed, the glowing lights high in the night sky do signify an alien intrusion: a property developer that has purchased another swathe of land to build the Brunel Street Works -975 homes of mixed tenure across buildings ranging from

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nine to 26 stories as well as commercial and leisure spaces. Evidently these cranes bring a promiseor a forewarning of the inexorable territorialisation of land for private development. | The red bridge and the River Lea Next, we walk across the 80-metre footbridge crossing the River Lea at Bow Creek, installed in 2014 to connect Canning Town to London City Island, another high-rise development delivering 1,700 apartments across 10 towers, varying between seven and 23 stories. The bridge connects future residents to Canning Town station and town centre, and is supported by a 20-foot-high steel beam and vertical struts, painted in bright red. We remark on how it is endowed with a special magic at night as its brilliant illumination dramatically contrasts with the muted, monochrome hues of the surrounding nocturnal landscape. The luminous structure provides an indirect glow that lights up our bodies and those of others, producing a linear stage in which pedestrians are an integral part of its nocturnal appearance, inducing an awareness of ourselves as part of the landscape. Though it signifies the instrumental, design-led, place-making transformation of the neighbourhood into a patchwork of semi-public spaces, the bridge is also a public amenity that enchants the nightscape. It exemplifies how the commercial imperatives that drive the redesign of many public spaces do not prevent residents from incorporating them into everyday socialising or playing (Degen et al., 2008). As we walk across the alluring bridge and appreciate the skilled engineering and lighting design invested in staging the passage between two different boroughs, we

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are conscious of contributing to its performative role in staging the surrounding environment. The bridge also offers an encounter with the non-human elements of this landscape, agencies that are unamenable to regeneration and gentrification and resist its orderly shaping (see Miéville, 2012), highlighting its artifice (Kullman, 2019). Looking down we see the flowing, rippling River Lea, nearing its entry into the Thames estuary from the Chiltern Hills, silver in reflecting the surrounding lights. The sloping banks of thick estuarine mud glisten either side of the murky waters, an implacable intrusion into this highly regulated realm of luminous towers and a tube station. We delight in the luscious, untamed viscosity that rebukes the smooth steel of the bridge and the sleek towers of London City Island, an inhuman, clammy substance that is as perilous and inconvenient as it always was. | Entering City Island The bridge telescopes us onto London City Island along a temporary wooden walkway and stairs around the building in progress. As we descend from the bridge, a dazzling visualisation of the future development is situated under a luminaire. The glossy CGI chimes with Degen et al.'s discussion of how such images are typically toned with a "visual luminescence" (2017, p. 8) that bathes not-yet-actualised urban scenes in a lively, convivial atmosphere. Such images, they contend, work "to depict and present specific embodied regimes and affective sensory experiences to appeal to clients and consumers" (2017, p. 8). This lambent image of London City Island sharply visualises the crystalline interiors of apartments, populated with busy

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or relaxing inhabitants, and a square packed with diners, pedestrians, and cyclists, socialising and hanging out. A vision of cosmopolitan, stylish urban living is orchestrated to suffuse the imaginary atmosphere, soliciting the attention of would-be-purchasers, and underpinning Kaika's suggestion that the symbolic authority of London's iconic architecture teaches "society what to desire and how to desire it" (2010, p. 458). We both admit that we are ineluctably lured by this fantastical vision. This anticipatory suggestion is augmented by a window in a temporary hoarding that reveals an unpopulated construction site, a still life composition of tools, machines, and construction materials, seemingly left midway through busy work, but soon to be sparked into motion the following morning. The site is glaringly floodlit to ward off intruders and enable CCTV footage to identify potential interlopers. This almost theatrical illumination stages the construction process like a public display of surgery in an operating theatre. We are temporarily mesmerised by the sight of illuminated interior spaces where metal beams provide support for grey plaster walls perforated with holes from which extrude spaghetti like bundles of cables. Like the Berlin construction sites that briefly served as tourist attractions (Till, 2005), this vivid spectacle honours and demystifies the labour required to build such a development while cultivating anticipation about the promise of an emerging place. | London City Island London City Island, in reality a 12-acre peninsula, was formerly a poor, working-class community known as Orchard Place. In the late 1930s, following frequent flooding, the remaining inhabitants were rehoused, and the peninsula

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housed ironworks and a vegetable oil refinery until the turn of the millennium. Promotional material indicates that the island is being reinvented as a "new exclusive island neighbourhood": "rising up at the point where the Thames meets the River Lea, London City Islandset against big river skies and stunning viewsis a cooler sibling to the mighty skyscrapers of Canary Wharf" (London City Island, 2017, p. 39). With a "nod to the area's artisan past," this development mimics the industrial warehouse aesthetic and loft apartment style described by Sharon Zukin (2010) in her critique of New York's gentrification. Indeed, the vertiginous design sought to create a "micro-Manhattan," yet with its own aesthetic identity "designed to be clearly, unmistakably that of London City Island" (London City Island, 2017, p. 62). Each of the 10 towering buildings have a distinctive colourblue, red, white, orange, blackto pay homage to the pigments deployed throughout the "history of artisan and maritime production" (2017, p. 61). Capitalising on the island's relative seclusion, the developer has been granted an ideal topography for recreating a self-sufficient environment replete with al fresco spaces, waterside parks, bars and restaurants, artist studios, boutique shops, a school, and a private residents' club, culturally augmented by the presence of the London Film School and the English National Ballet's headquarters. Echoing Florida's (2005) mantra that the so-called "creative class" are the drivers of urban development, London City Island is marketed as the ideal home for "creatives"; online you can meet four such creative "islanders": a photographer, a film maker, a ceramics

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artist, and an animator. Like most residential towers, the island's skyline is not illuminated by extensive exterior lighting but gains luminescence through interior, domestic lighting, looming subtly against the black backcloth of the sky. The soft light spilling from these interiors and glowing lower ground floors complements the prevailing aesthetic of indirect lighting, carefully integrated into furniture and buildings (Ebbensgaard, 2019b). The lighting scheme's soft glow produces an intimate, ambient atmosphere that extends the domestic intimacy of a cosily lit home to create a sense of communal domesticity in shared living space: people arrive "home" to a realm in which to enjoy "boutiques, delis and restaurants spilling out into the night air" (London City Island, 2017, p. 93). Here, the nocturnal field of the visible solicits a sense of shared economic and cultural privilege. Walking through this not-yet-populated space, we cannot help but feel beguiled by the ambient glow and reflect in discussion that this "invitation to attune" (Sumartojo & Pink, 2018, p. 121) fosters a powerfully consensual distribution of the sensible. The affective allure elicits the kind of "seductive logic" that, as Allen (2006) suggests, exercises its power not through exclusion but by conveying an illusory impression of inclusiveness; we feel invited inside the sensory boundaries of this regime where dissensus has been smoothed away by aesthetic consent (cf. Julier, 2005). But before long, this aesthetic regime starts to crumble. | Walking along the Aspen Way Leaving London City Island behind, we find our way to the Aspen Way. Like the A13 flyover, this elevated

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concrete structure epitomises a singular modernist functionality: walking is a strictly subsidiary activity, and this stretch of road is defined by automotive servitude rather than "noctambulation." Bathed in sodium lights, the structure forms a golden river that cuts through towering developments typically illuminated in blue and white. Replete with "light clutter," the disparate lighting includes orange streetlights, illuminated tower "crowns," lurid advertising hoardings, neon shop signs, domestic illumination, and residential garlands, while the head and tail lights of vehicles and the internal glow of the DLR surge and fade. Light clutter is commonly decried by dark sky campaigners as a form of light pollution and by light designers, who contend that it reduces legibility and diminishes a clear sense of place (Major, 2015). Yet for us, in spilling from interior realms, signage, and moving vehicles, this illuminated excess bestows public space with vitality and signs of life (Ebbensgaard, 2019a). Indeed, this cluttered scene avoids the distinctive master planning aesthetic that informs the design of London City Island and persists in other sterile, homogeneous nocturnal environments (Edensor & Millington, 2018). Moreover, it reveals that some areas of this part of east London have not succumbed to the intense pressures of property development. The diversity of the lighting technologies and aesthetics we behold discloses the contingency of urban planning and development processes, contributing to the production of time-deepened, complex lightscapes ( Figure 2). More specifically, the predominance of the increasingly obsolete high-pressure sodium lights adds texture to the air and grain to the street, enchanting the regimented roadscape

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with an orange wash. While these serialised, standardised, and uniformly installed streetlights evoke a pure functionality, we suddenly sense that we are walking through multiple histories and an ever-emerging nightscape that is once more being reconfigured. Being bathed in the sodium luminosity is charged with a familiarity borne of its former ubiquity, as it suffuses embodied perception, generating a haze before the eyes and draining the colour from faces. Immersed in the orange glow, we discuss how we both feel subsumed by a curious nostalgia, situated amid the familiar sensations of the past and the emerging lightscape of the present. The complex layering of overlapping and intersecting temporalities becomes especially evident when walking through illuminated nightscapes, reminding us that we too are part of the histories of diversely illuminated cities. | Poplar Dock Disoriented by the heavy flow of traffic on the Aspen Way, we take a path away from a large roundabout and find ourselves in a wholly different illuminated realm: a vast, much darker space surrounding an inner dockthe fashionable Poplar Dock Marina. As we approach the marina, couched by willow trees to the north, a cluster of high-rise buildings descending southwards on the east side, and low-rise residential buildings on the opposite side, the hum from traffic fades. Striking vernacular and fashionably designed forms of lighting jostle for attention. A billowing landscape of inhabited narrowboats, tugboats, sailing boats, and rowboats connected by a floating network of pedestrian platforms furnished with informal light chains, interior lighting, and moving lights. Their homespun appearance contrasts with

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the minimalist street lighting and illuminated windows of the adjacent residences that are reflected in the still waters, a medley of white, yellow, and red smears supplemented by two vertical, cobalt blue lines of light that vividly outline the sides of a building. Reflections of the rippling water play in the glass facades of the residential building balconies, while the soft yellow glow streaming through the drawn curtains of the windows of a narrow boat, also reflected in the water, offer a sense of intimacy within this somewhat secluded oasis. As we slow down and chat in whispers, we are reminded of the "invitation to attune" to this quieter and calmer realm. Yet far away, high in the Horizons Tower, a wholly more animated scene emerges: the flashing, changing colours of a party, pulsing illuminated signs of human activity made strange by the lack of any discernible musical sounds. Initially we feel as if we are missing out on what might be a joyous, riotous occasion. In the calm, hushed atmosphere of the dock, the flashing lights accentuate the vertical stratification of populations (Graham, 2015), spawning an imaginary of the secluded, luxury lifestyles of glamorous Londoners (Atkinson, 2016). For us, popular cultural representations continuously swarm through our apprehension of the world, and as Macpherson asserts, we never simply perceive an unmediated reality for "seeing involves movement, intention, memory, and imagination" (2009, p. 1049). The animated lights in the tower provoke us into making sense of this nocturnal scene; following Mitch Rose, it transformed "the vagaries and

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