A streetlight serves two purposes, in theory: to make travel safer by illuminating obstacles, and to deter crime by literally bringing shady dealings to light. Whether those beacons actually achieve their goals, however, is a matter of controversy; now, a team of British researchers argue streetlights don't really prevent accidents or crime, but do cost a lot of money.
Perhaps it's just a fear of the dark, but for city dwellers, a poorly lit street is a warning sign—do not enter. Yet like many of our fears, that panic may not necessarily have a basis in reality. Research on the connection between crime, violent or otherwise, and the presence and brightness of streetlights is a mixed bag. A study commissioned by the Chicago Department of Transportation, for example, found that, while crime went up during streetlight outages in some neighborhoods, there was no effect in others, and in one neighborhood crime actually went down. Likewise, there isn't a clear connection between street lighting and traffic accidents.
While there were faint hints that crime might be reduced under dimmed lights or whiter LED lamps, overall the type and intensity of street lighting had no effect on crime.
At the same time, building and maintaining street lamps is costly. The City of Boston estimates they operate around 64,000 streetlights at a cost of about $8 million annually, and it takes about £300 million to operate and maintain all the streetlights in the United Kingdom. Much of that money goes to the electricity it takes to keep all those lights on, so apart from the monetary cost, there are also environmental ones.
In other words, if streetlights aren't preventing crime or accidents, they might not be worth the money, Rebecca Steinbach, Phil Edwards, and colleagues at University College London and the London School of Hygiene and Tropical Diseases argue today in the Journal of Epidemiology and Community Health. To find out, the researchers examined data on streetlights from 62 local governments in England and Wales between 2000 and 2013, a period when budget pressures led many of those authorities to cut back on streetlamps and other infrastructure. Then, by comparing traffic and police statistics before and after those changes, the researchers could ask whether turning down the lights might have an effect on collisions and crime.
In short, lighting had no effect, whether authorities had turned them off completely, dimmed them, turned them off at certain hours, or substituted low-power LED lamps. In spite of intuitions and anecdotes, the researchers found no connection between the type or amount of lighting and the number of nighttime traffic accidents. And while there were faint hints that crime might be reduced under dimmed lights or whiter LED lamps, overall the type and intensity of street lighting had no effect on crime, either.
"[W]hen risks are carefully considered, local authorities can safely reduce street lighting saving both costs and energy ... without necessarily impacting negatively upon road traffic collisions and crime," the team writes.
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