Street Lighting Switch off – are the Roads Just as Safe?

There has recently been a lot of publicity given to some research that appears to show that switching off street lighting makes no significant difference to things like the number of road traffic accidents or the rate of crime.

The study lead by researchers at the London School of Hygiene and Tropical Medicine in collaboration with the Department of Security and Crime Science at UCL was commissioned due to fears that reduction in the provision of street lighting may be causing increases in crime, injuries and deaths.  The study took data from 62 self-selected local authorities in England and Wales who had made changes to their lighting. The study used the standard record of traffic collisions STATS19.  It should be noted that the data in this resource are usually recorded when police attend the crash, this means that its reports are biased towards more serious incidents particularly those where someone is killed or seriously injured.  The crime information that they used was the recorded crime from the Police.uk website.

I do not here wish to comment in too much detail on the results of this study with respect to crime as this is an area in which it is difficult to get reliable data due to variability in recording practice with time and location.

The researchers used a fairly logical approach to dealing with the data that they got for road traffic collisions working with the day-time to night-time accident ratio for the roads where the lighting had been changed.  This sort of approach usually works as it automatically compensates for overall changes in road use and traffic flow, providing that the changes have been uniformly spread across the 24 hour cycle of road use.  However, the assumption that the ratio of night-time to day-time traffic would remain fixed after an intervention in street lighting was not checked in the study.  Moreover, it is known that poor street lighting can be a deterrent to street use at night particularly for pedestrians.

The key finding of the report that switching off street lights together with a number of other interventions in street lighting make very little difference, and this finding must come as something of a relief to authorities who have switched off their lights.  However, switching off lights was always a contentious way for an authority to save money and this study, because of what it looked at, cannot in itself say that turning lights off has not had an impact.  There are two basic problems; firstly, as switch off has been contentious authorities have been reluctant to do it, hence the study was only able to find 5 authorities that had done it. It is also known that in some cases of switch off additional accident countermeasures were taken, such as repainting road markings.  The second and perhaps more major problem is that if, as seems likely, the removal of street lights reduced pedestrian street use at night in the affected areas then and the level of risk to each pedestrian had remained the same then there should have been a fall in the number of collisions involving pedestrians.  So what may well be going on is that some pedestrians have been killed and injured as a result of the lighting switch off but as the number of people on the street has been reduced then the overall number of people who have been injured or killed remains the same.  If this is the case it will explain the statements like those from the AA that there have been several inquests into road deaths that had blamed the deaths on the absence of lighting.

Thus we have an interesting situation where the casualty rates on a given road do not appear to change when lights are switched off but the risks to a road user on that road may have increased.