Researchers have found that vehicles are much more likely to be broken into on a road with bright overnight lighting than on one where street lamps are switched off after midnight.
The study team believe opportunist thieves are less inclined to target cars that are left in the dark because it makes it harder for them to see inside, evaluate security and remove parts without anyone noticing.
The researchers analysed crime statistics from Thames Valley Police, along with data on changes to street lighting in Oxfordshire, Reading, West Berkshire and Wokingham between April 2004 and September 2013. They assessed the differences between lamps being kept on all night and the gradual changes to their timing and brightness over the nine-year period.
This included lights being switched off between midnight and 5am, using white all-night lighting and dimming lighting in the early hours.
The results showed that thefts from vehicles plummeted by 44% when street lighting was turned off between midnight and 5am.
While overall criminal activity was still found to be more common after dark, the number of offences did decline over the years analysed.
The research, published in the Journal of Quantitative Criminology, also found that switching off lighting in certain streets led to a rise in vehicle thefts in neighbouring roads that remained lit throughout the night.
But when crimes committed at any time of the day were included in the analysis, the changes to lighting showed a drop in overall crime, burglary and violence on both the focal streets and the nearby ones.
While previous research has shown that switching off street lights doesn’t increase crime, this new study suggests that it might even reduce some types of offence.
Dr Phil Edwards, from the London School of Hygiene & Tropical Medicine (LSHTM), said: “It is to do with opportunist theft. Without lighting it’s harder to see the laptop left overnight by accident on the passenger seat, for example.”
Generally, the researchers felt that switching off lights is beneficial but acknowledged that the issue is complex.
Dr Edwards added: “It is clear from other studies that people like street lighting, it makes them feel safer. But studies like ours are showing that actually the effects of street lighting aren’t that clear.”