Costing lives or saving lives: a detailed evaluation of the impact of speed cameras.

The real problem with speeding is that it is socially acceptable. Most drivers speed but are rarely involved in crashes. Police tolerance to marginal speed limit infringements is assumed, the likelihood of detection is perceived as low and fixed penalties are not considered particularly severe. High performance vehicles with speed capabilities well in excess of maximum national speed limits are not illegal but rather are considered a symbol of personal success. The result is that speeding is not perceived as dangerous, criminal or immoral but rather is considered the norm. Attempts to enforce speed limits tend to be unpopular, being viewed more as an infringement of personal liberty than as a curb on anti-social and potentially lethal behaviour. The evidence for the safety benefits of reduced speed is, however, strong. Certainly the basic laws of physics suggest that lower speeds will reduce both accident frequency and severity: lower speeds reduce both stopping distances and the energy dissipated in a crash. Available evidence does indeed confirm that both accident frequency and severity fall with reduced speeds (see, for example, McCarthy (2001), Stuster et al. (1998) and Taylor et al. (2000)). What is less clear is how best to ensure that drivers maintain safe speeds. While a wide range of approaches has been tried, speed enforcement cameras have undoubtedly attracted most public attention, frequently making headline news as, for example, happened recently following the publication of an evaluation of the UK national safety camera programme (Gains et al. 2004) Certainly for those responsible for road safety, speed enforcement cameras are seen as a way of increasing the perceived risk of prosecution for speeding and hence raising drivers awareness of the dangers, and the unacceptability, of excessive speed. However, although the rapid proliferation of cameras in recent years has undoubtedly increased the perceived risk of prosecution it has not fundamentally changed attitudes to the consequences of excessive speed. Critics have suggested that the primary objective of cameras is to raise money rather than to improve road safety and there have been claims that they may actually cost lives. While most of the criticisms of speed cameras are spurious (PACTS 2003, Mylius 2004), arising from a social climate that continues to consider the speed and the personal liberty afforded by cars desirable, the use of speed cameras continues to be controversial.