July 29, 2015

expert reaction to study investigating switching off street lights, levels of crime and numbers of car crashes

The effects that different strategies for lighting streets at night (such as partial, dimmer or no lighting) might have on crime and car crashes is the subject of a paper published in the Journal of Epidemiology and Community Health, in which the authors report that there was little evidence for harmful effects due to changes in lighting.

Prof. Kevin McConway, Professor of Applied Statistics, The Open University, said:

“The researchers did a decent job with the data they had available, but one really can’t conclude too much. There’s a big difference between absence of evidence for something, and evidence of absence. It’s fair to say that the study found little evidence of harmful effects of reduced street lighting, but despite the headline of the press release, we can’t be entirely confident that harmful effects don’t exist.

“One issue is that the researchers could get data from only about a third of local authorities. The study itself points out that they might not be typical of all local authorities, and that even, perhaps, some did not participate because they had increases in car crashes or crime. It’s interesting, for example, that they got no data from most authorities in north-east-England or Cumbria, the parts of England where winter nights are longest.

“Also, the overall picture that lighting changes don’t affect crime does, as the report explains, emerge from averaging over some police forces where there was strong evidence for an association between lighting changes and an increase in crime, and others where there was strong evidence the other way.

“Overall we’re reassured by this study that the lighting changes so far weren’t disastrously bad in their effects on road safety and crime. But because it’s an observational study, we can’t be sure why that is. The implications for future policy really aren’t clear. The report suggests that street lighting can safely be reduced “when risks are carefully considered”, but the data don’t allow much to be said about exactly how to consider the risks, or about how much scope there is for further safe reductions beyond those already made. It’s not a blank cheque for further turn-offs and dimmings.”

‘The effect of reduced street lighting on road casualties and crime in England and Wales: controlled interrupted time series analysis’ by Rebecca Steinbach et al. published in the Journal of Epidemiology and Community Health on Wednesday 29 July 2015. 

Declared interests

Prof. Kevin McConway declares no interests.