A REVIEW OF THE LITERATURE ON POLICE TRAFFIC LAW ENFORCEMENT

The review covers three main aspects: the effect of enforcement on traffic crashes, the effect of enforcement on driver behaviour, and alternatives to coventional enforcement. Most studies attempting to examine the effect of enforcement on crashes have simply considered changes in total crash numbers after a general increase in enforcement, some studies have considered particular locations or times of day, whilst others have concentrated on particular offences. Most studies have contained serious faults in either planning or evaluation. Those reviewed indicate that it is possible to reduce traffic rashes using enforcement given the right circumstances and correct type of site. A deployment plan based on high-risk locations or times appears superior to a general increase in enforcement. Most well-planned studies of enforcement have been concerned with its effects on driver behaviour. There is good evidence that the presence of an enforcement vehicle will cause a reduction in driving speeds, and that this reduction may be maintained for up to 5 km; a memory effect may also be produced by a period of concentrated enforcement. Alternative methods of enforcement have included dummy patrol cars and automatic speed indicators. Public posting of speeding behaviour and road safety posters have also been used. Most of these methods have achieved some success in modifying driver behaviour, but they have not been tried on an area-wide basis. (Author/TRRL)