MERLIN-2: Further empirical evidence of lighting for pedestrians

When travelling to local destinations, safer streets encourage people to walk rather than drive. That is beneficial in many ways: walking promotes good health and interaction with the community and less driving reduces pollution. After dark, good road lighting contributes to pedestrian safety. Good lighting can make a place feel safer by improving visibility of the route ahead and improving the visibility of other people. Good lighting can make a path safer for pedestrians by improving the ability to detect potential trip hazards in time to take avoiding action. However, there is currently insufficient knowledge of what 'good lighting' is. While the public generally respond favourably to increasing light levels, there must be consideration to the energy consumed by the lighting and that at some point, increasing the light level does not increase the visual benefit of lighting.

Recent work has suggested that we can reduce light levels without reducing the visual benefit of lighting because light levels are un-necessarily high and by optimising the trade-off between the colour of lighting and the spatial distribution of light. Reducing light levels offers a rapid route to reduction in energy consumption and hence in the greenhouse gasses associated with electricity generation, a demand-side approach to meeting current carbon-reduction commitments. Reducing light levels reduces the amount of light reflected to the night sky, and reduces the impact of nocturnal lighting on wildlife and human health.

The proposed project will investigate road lighting in residential areas, which is designed to meet primarily the needs of pedestrians. We will first clarify our understanding of what matters to pedestrians - what it is they need to see for safe walking. This will be done through a new analysis of eye tracking data from pedestrians walking outdoors after dark, videos which show where someone looks, to reveal the critical objects of attention and how far ahead we would like to see them. Experiments will be carried out to explore how lighting affects our ability to evaluate the intention of other people (e.g. whether friendly or threatening) and to detect potential trip hazards, and how lighting affects perceived safety: our recent work suggests these are the critical tasks for safe walking.

The aim of this work is to improve understanding of the visual needs of pedestrians walking along pavements after dark, thus to ensure that (1) these needs are included within guidance for the design of road lighting, and (2) the cost-benefit analysis of road lighting provision is better informed as to the benefits for pedestrians. These needs include their evaluations of the environment such as perceived safety, and their ability to see trip hazards and other people in sufficient time to take avoiding action if necessary. Better lighting has the potential to reduce fear of crime (either directly through improved visibility or indirectly through improved community pride) which in turn encourages walking as a choice for local transport, promoting good health. It may also alleviate psychological distress caused by fear of crime which leads to some people remaining prisoners in their homes, primarily associated with the elderly and females. Lower light levels yield lower light pollution which is of benefit to those who observe the skies at night. This work will be carried out alongside our planned studies of lighting for cyclists, wheelchair users, studies of lighting and crime / accidents, and implications for dark sky observation and environmental impacts.

Results obtained in recent work suggest that light levels can be reduced, partly because current guidance recommends levels that are too high, and partly through a trade-off with the colour and spatial distribution of light. This reduction can be achieved without reducing the benefits of lighting in supporting vision.

The direct beneficiaries of this research are local authorities who are responsible for the provision and maintenance of road lighting in residential areas. They will gain improved design guidance and lower light levels will lead to reductions in energy consumption, energy expenditure and carbon emissions. The current method of specifying street lighting focuses primarily on horizontal illuminance and it is clear that there are other requirements for the lighting: LED lighting makes it possible to focus directly on lighting the road and MERLIN research has shown we need to amend the current standards to ensure that vertical illuminance is maintained. Manufacturers of lamps and lanterns used for road lighting will benefit through the establishment of improved lighting design criteria as targets for value engineering. The new guidance will be developed initially through committees set up within national (ILP) and international (CIE) organisations. These committees comprise representatives of lighting research, design, installation and manufacture, and are tasked with reviewing a wide range of evidence associated with road lighting. Guidance reports from these organisations will influence the next revision of BS5489-1, the critical document for road lighting in the UK.

Implementing this guidance will be of benefit to the general public who walk along roads at night or who wish to observe the environment at night. Better lit roads encourage a reduction in the use of motorised transport for local journeys: this is a means by which physical activity can be introduced into people's daily routines in order to encourage good health, and a reduction in the noise, exhaust emissions and congestion associated with traffic. Lower light levels reduce light pollution. Light pollution of the sky (skyglow), including road lighting reflected from pavement surfaces, reduces the visibility of stars. Road lighting that crosses the boundary of a property (light trespass) can be annoying to the resident and is generally wasted light. Lower light levels reduce these problems, offering an alternative or complementary option to the strategies of switching off road lighting or limiting the region of the visible spectrum available for road lighting. It may be an advantageous strategy because it enables the visual benefits of lighting for road users to be maintained.