Compulsory use of Daytime Running Lights (DRL) was introduced in Denmark on October 1, 1990, for all motor vehicles. The effect on road safety was first investigated by using accident data for the first five quarters, after the law became effective. Results of this analysis were published in February 1993 (see IRRD 859229). The analyses have now been repeated based on accident data for 11 quarters after the introduction. Main results are largely unchanged when the after-period is extended to 11 quarters. Therefore, it may be concluded that the effect is permanent and not a short term phenomenon that could only be registered when DRL were new to road users. For accidents involving pedestrians no DRL impact was found in the first pedestrians no DRL impact was found in the first evaluation, but with use of a longer after-period there seems to be a significant increase after the introduction of DRL. It has, at the moment, not been feasible to determine if the increase can be attributed to DRL. No significant effects have been found for other accident situations, but there seems to be a positive impact on accidents involving bicycles, and a minor negative impact on accidents involving motorcycles. However, use of DRL was made mandatory for motorcycles already in 1977, and therefore a negative impact on accidents involving motorcycles was expected. For calculation of effects a log-linear model has been used. In other nationwide DRL evaluations, the effect has been estimated in quite a different way. As results are very dependent on the evaluation method, this paper ends up with a short discussion of statistical methods. (A).
Abstract