There is a substantial body of evidence which shows that DRL are effective in reducing daytime crashes, but studies disagree as to the size of the reduction. It is therefore difficult to predict what impact they might have in Australia. The best technical option for DRL appears to be dedicated DRL with an intensity of 1200 candelas, designed to direct its light towards oncoming vehicles, and with reduced power requirements. Dipped headlights direct most of their light at the road surface and have higher power requirements. Dedicated DRL have favourable benefit-cost ratios, while full-time operation of dipped headlights has a benefit-cost ratio close to one. The costs of providing DRL would be considerably reduced if the DRL operated only in conditions of low ambient lighting. Although visibility experiments suggest these are the only conditions under which DRL are of benefit, there are no studies available which relate crash reductions to ambient light conditions, so that it is not clear how much of the benefits associated with full time operation would be realised. (Author/publisher)
Abstract