Increasing visibility of speed cameras might increase deaths and injuries on roadsBMJ 2002; 324 doi: https://doi.org/10.1136/bmj.324.7346.1153/a (Published 11 May 2002) Cite this as: BMJ 2002;324:1153
EDITOR—In December 2001 the government announced changes to the colour and positioning of speed cameras.1 But what will the effect be on deaths and injuries caused by road traffic collisions related to speed? And where is the evidence for this change in policy?
Interventions to control speed seek to reduce both the likelihood and the severity of a collision. The setting of appropriate speed limits is a major strand of this preventive action, and speed cameras are one of the main methods of enforcing these. The effect of speed cameras on road traffic collisions is well documented. A study in London showed that deaths fell threefold, and a trial in eight police force areas saw a reduction in deaths and injury after the introduction of cameras. 2 3
Speed cameras will now be painted yellow and must be visible from a distance of 60 metres (66 yards) on roads with a speed limit of up to 40 mph (64 km/h) and 100 metres (109 yards) on roads with a speed limit above that (figure). Police forces will also be forbidden from erecting warning signs on roads where there are no cameras.1
These measures seem designed to placate the angry minority of motorists who believe that drivers should be warned about impending cameras, giving them the chance to slow down. But this view is not based on evidence of health benefits. Hidden cameras are associated with net falls in speeds, crashes, and casualties when compared with visible ones.4
Increasing the visibility of cameras and banning dummy warning signs removes the uncertainty of where cameras are located. But this uncertainty is one of the only means of discouraging widespread speeding. Has the government given up on its goal of tackling the culture of speeding? Speeds may drop in the 183 metres (200 yards) either side of a camera. But there will be no disincentive for drivers to keep within limits in areas free of cameras. Persistent speeders are the most likely to report driving slower in the presence of cameras but no differently or faster in other areas.5
The introduction of high visibility speed cameras is a mistake. We need evidence that they are more effective than hidden cameras. If they do not reduce collisions, deaths, and injuries more effectively they should not be introduced. Road safety policy should be based on evidence of health benefits and not on pressure from a vocal minority.