16.02.2022

The science of street lights: what makes people feel safe at night

Winter is coming: the nights are drawing in and in the Northern Hemisphere the hours of darkness already outnumber the hours of daylight. Research has shown that darkness produces a big fall in the number of people out walking – and a major reason for this is that people feel less safe walking in the dark.


There may be an evolutionary explanation for why people feel less safe at night – we can’t see as well, and this may have exposed our ancestors to greater threat from predators. Nowadays, it’s not so much the prospect of being eaten by a savage beast that concerns would-be pedestrians, but the fear of being mugged or victimised.


Some studies suggest that new outdoor lighting can reduce crime rates in an area, but there is conflicting evidence on this. A large review of research found a link between new lighting and reduced crime rates, but improvements were seen in daylight as well as darkness, suggesting that solar led street light is not the only factor. This review has also been criticised by other researchers, and a large statistical analysis found no link between crime rates and switching off or dimming street lighting at night.


Street lights may or may not have an effect on crime, but one thing’s for sure – brighter levels of light do make people feel safer when walking at night. This can lead to a significant increase in the number of minutes people spend walking each week. It can also reduce the number of people who avoid leaving their homes at night, reduce social isolation, improve physical and mental well-being and increase community pride.


Street lighting can improve the quality of neighbourhood life by making people feel safer – but, even so, it would be unwise to flood our streets with light at night. Street lighting costs money: the UK’s annual bill is estimated at around £220m. Artificial light at night may also have a negative impact on wildlife and the natural world, for example by stunting the growth of frogs and toads and preventing them from laying their eggs.


The skyglow from street lights also means we rarely get to see the true wonder of the night sky, frustrating astronomers and limiting our appreciation of the natural environment. For these reasons, lighting should be used selectively and efficiently – and this requires good guidance to help those responsible for installing and maintaining our street lighting.


The guidelines for street lighting in the UK and many other countries are currently based on questionable evidence. That’s why our lighting research group at the University of Sheffield undertook a programme of research to find out how lighting relates to feelings of reassurance after dark, and improve the evidence on which lighting guidelines are based.


Illuminating evidence

In one recent experiment, we asked people to walk along a number of streets in the city of Sheffield at night and rate how safe they felt. We also asked these people to walk and rate the streets in the day, to create a baseline measure of safety and to account for biases that may occur if safety ratings were taken only after dark.


The difference in safety ratings between the day and night walks told us something about the lighting on that street – the smaller the difference between day and dark ratings, the safer people felt due to the lighting. We compared our participants’ different ratings against measures of the lighting on each street, including the average illuminance (amount of light falling on the street surface) and uniformity (how evenly spread out the lighting was).


Today, average illuminance is the main measure used when installing and evaluating led street light. But we found that, while increasing average illuminance was linked with improved feelings of safety, uniformity was more important for making people feel safe. So it might be more important to have evenly distributed lighting, rather than bright lighting, to make people feel safer.


Local authorities are undergoing major changes to their lighting, as they replace the traditional orange sodium lamps with new LED lighting. These new LEDs are more energy efficient, which saves taxpayers’ money. They also give councils greater control over the lighting they provide, for example by dimming and switching off when there are no pedestrians about.


Used properly, street lights can improve people’s lives and help neighbourhoods come alive at night. But there’s still a lot to discover about how people respond to street lighting and the impacts it has on society and the environment – experiments such as these can help to light the way.


Financial and carbon reduction incentives have prompted many local authorities to reduce AIO Solar LED Street Light at night. Debate on the public health implications has centred on road accidents, fear of crime and putative health gains from reduced exposure to artificial light. However, little is known about public views of the relationship between reduced street lighting and health. We undertook a rapid appraisal in eight areas of England and Wales using ethnographic data, a household survey and documentary sources. Public concern focused on road safety, fear of crime, mobility and seeing the night sky but, for the majority in areas with interventions, reductions went unnoticed. However, more private concerns tapped into deep-seated anxieties about darkness, modernity ‘going backwards’, and local governance. Pathways linking lighting reductions and health are mediated by place, expectations of how localities should be lit, and trust in local authorities to act in the best interests of local communities.


Electric street lighting has been a feature of urban and suburban settlement since the end of the nineteenth century. Indeed, the electrification of lighting has in many ways defined the modern city, in extending the visibility of its public spaces, inhabitants and itinerants beyond the hours of natural daylight (Martland, 2002, Otter, 2002) and changing the meanings of the night for city dwellers (Schlör, 1998). However, in many areas of England and Wales, as in other countries, the taken-for-granted assumption that streets and public spaces will be lit at night has been disrupted in recent years. Many local authorities responsible for LED Street Lighting Solar have reduced street lighting at night, a policy primarily driven by requirements to reduce costs and carbon emissions under the Climate Change Act 2008 (Department for Environment Food and Rural Affairs (DeFRA), 2011), but also with considerations of contributing to reductions in environmental light pollution (The Royal Commission of Environmental Light Pollution, 2009). A rapid growth of technological innovations over the last 20 years has enabled greater control over the colour, intensity and switching on schedules of public lighting stock (Shaw, 2014a), and local lighting authorities across England and Wales have adopted a wide range of interventions. These include: removing, or switching off lanterns in street light columns (‘switch off’); reducing the number of hours that they are switched on (‘part-night lighting’); replacing sodium lanterns by ‘white’ LED light; and ‘dimming’ lanterns through centrally managed systems. Some of these interventions reduce the amount, or duration of, artificial light at night. Switch off and part-night lighting result in dark streets which were once lit, at least for some of the night time hours.


Changes which reduce lighting, particularly ‘switch off’ and part-night lighting in urban areas, have attracted considerable public and media concern, centring on crime, fear of crime, perceptions of safety, and road safety. These are all important determinants of health and wellbeing: directly in the case of road safety; and indirectly, in that fear of crime, for instance, has multiple pathways that impact on mental health (Lorenc et al., 2012). To date, empirical research on fear of crime and perceptions of safety have focused largely on improvements to lighting, with the assumption that more lighting will improve security, and reduce fear of crime (Lorenc et al., 2013). However, empirical findings on the impact of improved lighting on perceptions of crime, personal security and road injury have been mixed, with no clear conclusions on how increased lighting does improve these health outcomes (Atkins et al., 1991, Painter and Farrington, 1997; Pain et al., 2006). A systematic review of the effects of increased street lighting on crime (Welsh and Farrington, 2008), including 13 controlled before and after studies, concluded that improved street lighting in public spaces did not reduce crimes at night any more than was observed during the day. The authors suggest that the protective mechanism of street lighting may therefore act more through increasing pride in the locality or social control, rather than directly increasing surveillance to deter crime. As Koskela and Pain (2000), suggest, ‘fear of crime’ is a complex outcome of the political and social meanings of space, including gendered meanings, and is unlikely to be deterministically tied to isolated environmental conditions such as public lighting. On road traffic injuries, Beyer and Ker’s (2009) systematic review also noted the poor methodological quality of research to date, and suggested more high quality evaluations were needed to adequately determine the effectiveness of street lighting for reducing the incidence of road traffic injury.


If research on how improved lighting impacts on health outcomes is inconclusive, that on reduced lighting is almost non-existent. There are no good grounds for assuming that the removal of a public good will have the reverse effects to those of providing or improving it. In addition, there are some rather different health outcomes that become the focus of reductions in artificial lighting. These relate to how reductions might mitigate the negative health impacts some have claimed from a growth in, and changing frequencies of, artificial light in the environment (Hölker et al., 2010, Falchi et al., 2011). Although the evidence base to date is weak (Vohra, 2013), a growing concern with light pollution as a potential hazard to health draws on studies of animals (Shuboni and Yan, 2010) and shift workers to identify disruptions in circadian rhythms and endocrine processes, which can affect sleep (Navara and Nelson, 2007) and, theoretically, health outcomes such anxiety, depression, obesity and even cancer incidence (Pauley, 2004, Fonken et al., 2009, McFadden et al., 2014). Broader public health concerns also include the more existential wellbeing effects of being able to see the night sky, and longer term environmental impacts of reduced carbon emissions (Claudio, 2009). The amount, and quality, of light at night has thus become a public health as well as political issue.


There have been some qualitative studies of public views of street lighting, identifying mixed and reflective views on the relationship between light and fear of crime, for instance (Pain et al., 2006). To date, though, there has been little research that directly addresses public views on the possible relationships between street lighting reductions and health more generally. To address this gap, this study therefore aimed to explore public views of the potential health and wellbeing impacts of reduced street lighting. We aimed to explore public understanding of the possible pathways through which street lighting might impact on health and wellbeing, and how reductions in street lighting were understood as impacting on health and wellbeing outcomes.

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