The Road Traffic Act 1991 incorporates legislation to allow information. recorded or measured by unmanned automatic devices to be admitted as evidence in proceedings in respect of speeding and traffic light offences without requiring corroboration. Since it is anticipated that the introduction of these red light and speed cameras will increase compliance with the law and hence reduce the numbers of accidents that occur due to red light running and speeding, the new legislation has been justified mainly on road safety grounds. In advance of the enactment of the legislation research was commissioned to examine the link between compliance at red light signals and road accidents in order to establish an approximate estimate (or range of estimates) of the proportion of accidents at signal controlled junctions in which red light running is a contributory factor. The City of Glasgow District was selected as the location for the research, in part because a number of red light cameras were being operated on a pilot basis there. Accident records for the period April 1989 to July 1991 were examined. The clear language description of each accident, written by the police officer who attends the scene of the accident were read, and judgements were made regarding the contribution of red light running to each accident. This analysis of records revealed that in the case of personal injury accidents red light running was the primary cause of the accident in 17% of cases, that it was a secondary cause in a further 1% of accidents and that it was a possible contributory cause in a further 8% of cases. An identical analysis replicated for damage only accidents found that red light running was the primary cause in 1% of cases, a secondary cause in 1% of cases and a possible contributory cause in 3% of cases. On the basis of this analysis, an estimate was made of the amount of money that would be saved if the introduction of red light cameras eliminated all red light running offences. The maximum potential saving in 1990 in Glasgow District was estimated as £1.82m; this reduced to £1.13m if the (one) fatal accident which occurred in 1990 was removed from the calculation. Of the total, £224k represented the maximum potential saying on damage only accidents, and the remainder the potential saving on personal injury accidents. It is highly unlikely that the introduction of cameras would eliminate red light running completely, and on the basis of research evidence from outwith the UK (Australia) it was hypothesised that savings would be approximately 20% of the maximum potential benefit if red light cameras were rotated amongst all sites in Glasgow District that were associated with a red light accident problem. Assuming a ratio of 1 camera shared among 10 sites (a ratio used widely elsewhere) and a concentration of the red light running problem on 175 of the 349 signal controlled junctions in Glasgow District, this reduced amount would be sufficient to recover the capital costs of treating the District with 18 cameras and 157 dummy units over 5 years. The research also found that accidents at signal controlled junctions which involve a red light violation are more likely to happen on wet or damp surfaces, on A roads and at crossroads, than those which do not involve a red light violation. These findings have implications for the effective siting of red light cameras. (A)
Abstract