Image: Leon Brooks via Wikimedia Commons

Across the UK, the lights are going out.  As local authorities seek to cut costs, street lights are being turned off or dimmed at night – with much local media concern about what this means for safety.  But is less lighting really a risk? Or are darker nights actually more likely to improve our health? The answer, as so often, entirely depends on whose health, where, and what kind of health we mean.

Public concern is understandable.  Until recently, most efforts were directed at installing more lighting, given the assumption that this improved safety.  This assumption was entirely in keeping with available evidence that improved lighting leads to both fewer traffic accidents and less crime.

We might expect, then, that recent switch offs have had catastrophic effects on road safety and crime. However, research suggests otherwise.  We know from the famous Hawthorne experiments, (in which workers’ productivity was observed to go up when lighting levels were raised –  but also when lighting levels were lowered) that we cannot assume a one way relationship between light and outcomes.  And sure enough, a recent study which pulled together 14 years of data from 62 local authorities in England and Wales, found no evidence at all that dimming or turning off street lights was associated with either more road injuries or more crime.  Indeed, the study found some evidence that dimming lights had reduced crime.

If there’s no evidence that reducing street lighting increases our risks, are local newspapers overplaying residents’ concerns?  Perhaps – but understanding why turning off the lights evokes such strong feelings involves more than counting road accidents and crime figures.


Image: Earth Lights via NASA

As Jane Brox so eloquently describes in her book Brilliance: the evolution of artificial light, the last couple of centuries have witnessed an explosion of light across the affluent parts of the world, changing the meanings of night, and the ways in which we live and work.  Urban dwellers now take the 24 hour city for granted.  Electric light also has political effects, across what geographer Robert Shaw has called the ‘fragmenting frontier’ of darkness: opening up the night creates possibilities, exclusions and oppressions.

london-810770_960_720 (1)

Image: London Night, Pixabay

Whether we personally benefit or not from the visibility of the modern city scape, we do expect it be there.  Brightly lit streets are an unremarkable feature of the modern world – only noticed when they are gone.  Keeping the lights burning has become a metaphor for good modern governance.  So much so that the lights going out can be psychologically devastating: when the US City of Detroit went bankrupt, for instance, residents were reportedly more concerned about broken street lights than failures of police response or fires in abandoned buildings.

So light at night matters: our urban and suburban streets feel safer when they are well lit.  When lights are turned off, concerns go rather deeper than those of crime or road safety. Fear of the dark is not unreasonable: in experiments, psychologists find that dim lighting encourages ‘morally questionable behaviour’.  Dark streets evoke abandonment, and a feeling that we can no longer rely on progress.  As one local resident said in our recent study of public views of reduced street lighting:

They go off at midnight – it’s hilarious, it’s like going back to the Dark Ages!

As well as worries about ‘going backwards’, residents talked about fear of walking in the dark, of being particularly visible to others when using a torch at night, and feeling that local councils had not listened to their concerns.


Image: Pinnacles at Night, Joe Parks

Others, however, particularly in more rural areas, were pleased that councils were turning off lights, and talked of the pleasures of seeing the night sky, and of feeling that, unlike city dwellers, they could ‘cope’ with the night.   Light pollution from abundant street lighting is not just a concern for astronomers: many people report wellbeing benefits of seeing the night sky and the meditative appreciation of our place in the universe.

There are also more concrete examples of the benefits of dark nights for health.  Studies of shift workers have long identified damaging effects from increased exposure to artificial light, which is thought to interfere with circadian rhythms and affect metabolism.   Evidence is accumulating on how even routine exposure to light at night might increase our risks of depression, stress and even cancer.   One intriguing study, for instance, found that obesity risks for women in the UK were higher for those whose bedrooms were lighter at night.

So there may be no evidence that turning off or dimming your local street lights will increase crime or traffic accidents.  But it might impact on how you feel about your neighbourhood at night, or the trust you have in the local council.  On the upside, it could also have benefits for your health: from the positive wellbeing effects of being better able to see the stars, to better sleep and even lower risks for obesity.

Electric lighting has, then, no inevitable impacts on human health: its effects depend on the meaning of light in particular places.  This is something professional lighting engineers in many local councils understand well.  In our study, they talked about having “the right light, in the right place”, a judgement that was made by balancing community concerns and the risks and benefits of particular lighting.  The largest threat to human health from street lighting perhaps comes from the erosion of their professional discretion, and the increasing pressure they are under to make decisions on cost grounds alone.