From May 1, 1988 the speed limit on Dutch motorways was increased from 100 to 120 km/h. For a limited part of the motorway network the limit is still fixed at 100 km/h. The introduction of this modification in speed limit was attended by information, publicity and an increased police control. In this report the effect of these measures on traffic safety in the period up to the end of 1988 is evaluated. Accident data are correlated with recorded speed changes in the before and after period. It is concluded that (1) the composition of measures, despite the increase of the speed limit, has produced a decrease in the actual driving speeds, (2) the decrease in speed has lead to a notable increase in traffic safety, (3) the safety aspects are not only limited to motorways, but also to other highway types, and (4) within the limited after period of eight months a decrease of the effects, and even in a given case a return to the old situation, is shown. Problems concerning the quantification of the effect, prognosis of effects with present policy and level of police surveillance, police control, and police enforcement are discussed.
Abstract