Lighting Research
at the School of Architecture, University of Sheffield

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MERLIN-2: Further empirical evidence of lighting for pedestrians

Dates: 2015 to 2018

Staff: Steve Fotios, Chris Cheal, James Uttley

Funding: EPSRC grant EP/M02900X/1, awarded to S Fotios, June 2015, £454,085.

Publications:

Fotios, S, Uttley, J, Fox, S. Exploring the nature of visual fixations on other pedestrians. Lighting Research & Technology. First published online, August 26, 2016. doi: 10.1177/1477153516666132.

Fotios, S, Uttley, J. Illuminance required to detect a pavement obstacle of critical size. Lighting Research & Technology. First published online, July 20, 2016. doi: 10.1177/1477153516659783.

Fotios, S, Castleton, H, Yang, B. Does expression choice affect the analysis of light spectrum and facial emotion recognition? Lighting Research & Technology. First published online, June 1, 2016. doi: 10.1177/1477153516651923.

Fotios, S, Castleton, H. Specifying enough light to feel reassured on pedestrian footpaths. LEUKOS, 2016; 12(4); 235-243. doi: 10.1080/15502724.2016.1169931.

This project will validate proposals for new design criteria for residential roads established in the MERLIN project, these leading towards lower light levels than current practice, reducing the energy consumed by road lighting (and thus also CO2 emissions) whilst maintaining the visual benefits of road lighting. This will be done through further analysis of the MERLIN data, further experiments using the apparatus and methods established in MERLIN, and field studies in collaboration with local authorities.

October 2016 update

Looking at important features: Further analysis has been completed of the eye-tracking videos collected during the first MERLIN project, in which pedestrians walked a real-world urban environment. The aim of this analysis was to better understand two critical visual tasks performed by pedestrians that were identified in MERLIN – looking at other people and looking for obstacles / potential trip hazards. The main conclusions of this analysis were that pedestrians had a tendency to first fixate other people at a distance of about 15 m, and for a duration of 500 ms. Detection of pavement obstacles tended to occur at around 3.4 m. These conclusions not only further our understanding of real-world visual behaviour, but also provide typical fixation characteristics that can be used to inform the design and interpretation of experiments about lighting, interpersonal judgements and detection of obstacles. For example, knowing what distance an obstacle is detected can help interpret data about illuminance levels required to detect at this distance. A review of literature about critical obstacle heights suggested pedestrians need to see obstacles of approximately 10 mm or greater, to avoid potentially tripping. Based on results from previous MERLIN research (Uttley, Fotios & Cheal, 2015), an illuminance of up to 0.9 lux is required to detect a 10 mm obstacle at 3.4 m. This finding is being fed into ongoing work with the international lighting organisation, the CIE, to update road lighting standards.


Figure 1. Example image from eye-tracking video, showing fixation at a trip hazard.

Light encourages walking: A key purpose of road lighting is to help people continue their everyday activities after-dark, such as travelling between places in the local area. Encouraging the use of active travel, e.g. walking and cycling, is a policy aim for many Governments, and road lighting may help support active travel after-dark. To examine whether light conditions do indeed influence the number of active travellers, data about pedestrian and cyclist frequencies in a district in the United States was analysed. A novel method was used to compare daylight conditions with after-dark conditions which controlled other factors that may influence the numbers of active travellers, such as seasonal variation and time of day. This involved comparing a one-hour period before and after the biannual daylight saving clock changes that occur every Spring and Autumn. This hour was selected so that the light condition was different before or after the clock change, being either dark or daylight. Analysis showed that the numbers of pedestrians and cyclists was significantly higher during daylight conditions compared with dark conditions when compared against changes in control periods when the light condition did not change. This effect was evident even when changes in daily temperature were accounted for. This finding shows the importance of light conditions on pedestrian and cyclist numbers, and supports the use of road lighting as a policy measure to encourage active travel.

Figure 2. Odds ratios comparing numbers of cyclists and pedestrians during daylight with after-dark, relative to control periods in which light condition did not change. Odds ratios greater than one indicate greater frequencies during daylight compared with after-dark. Error bars show 95% confidence intervals, p = 0.05.

Ongoing work: A further important role of road lighting is to make people feel safe when out walking after-dark. An experiment is currently being planned to better understand the impact lighting has on feelings of reassurance, and to identify the best lighting conditions for making people feel safe. In the experiment participants will be asked to rate how safe and secure they feel on different streets, both during the daytime and after-dark. The difference between these day and dark ratings gives an indication of the relative effectiveness of the road lighting in making the street feel safe, or at least as safe as during daylight. In addition to these ratings of safety, physiological and eye-movement measures will also be recorded. This data provides alternative emotional and behavioural information about the participants’ reactions to each of the streets under daylight and after-dark conditions, which will provide further information about the impact of the road lighting on how safe the participants feel. This experiment is due to begin by the end of 2016, and will be carried out by Aleks Monteiro, a new PhD student who has started in the Lighting Research Group.