Relationship between active travel and lighting

Darkness discourages people from walking or cycling, but there are good reasons to think that road lighting may help to address the fall in active travellers when it turns dark. We know that being able to see potential hazards in the path or road is a critical task for pedestrians and cyclists, and lighting can help make such hazards easier to spot. We also know that lighting can make vulnerable road users such as pedestrians and cyclists feel safer by making them more visible to drivers, reducing the risk of being hit by a vehicle. The fear of crime and perceived threat from others can also prevent people from travelling at night, but we know that lighting can increase feelings of reassurance and make people feel safer.

To maximise the benefits of lighting for active travel we need to know how lighting characteristics relate to walking and cycling behaviour. This can help us provide effective and efficient lighting, ensuring we do not waste energy or provide excess light pollution. We have begun work to identify the relationship between lighting and active travel, by comparing cycling rates after-dark to a measure of lighting – the relative brightness of a road, based on aerial images captured at night.

We quantified the effect of darkness on the number of people cycling at 48 locations in Birmingham, where automated cycle counters were situated. The effect of darkness was measured using an odds ratio, comparing changes in numbers between daylight and darkness in a specific hour against changes over the same time period but in a different hour, where the ambient light remains constant. The larger the odds ratio, the greater the reduction in cyclists after-dark. The brightness of the road or path at each of the 48 cycle counter locations was estimated using average pixel intensities from night-time aerial photography images. These pixel intensities were converted to approximate estimated illuminances, based on previous validation work carried out by researchers at Birmingham University.

Figure 1 shows the relationship between the reduction in cyclists after-dark at each location (as measured by the odds ratio) and the estimated illuminance at that location. This suggests a nonlinear relationship between light levels and the reduction in cyclists after-dark. Small initial increases in illuminance significantly reduce the negative impact after-dark conditions have on cyclist numbers, but this effect plateaus.

These initial results confirm that lighting can have a positive effect on active travel after-dark. Further work is needed to validate these results and use more accurate lighting measurements using on-site measurements rather than estimates from aerial photography.