The Swedish Transport Administration has since 2008 undertaken to review speed limits on the national road network. The aim of this study is to describe and analyse the long-term traffic safety effect of increased and, reduced speed limits. The results show that in total about 17 lives per year have been saved on the road network with changed speed limits. Results show an extensive reduction in fatalities on rural roads with reduced speed limit from 90 to 80 km/h. The number of fatalities decreased by about 14 per year . No significant changes were seen for the seriously injured. On motorways with an increased speed limit to 120 km/h, the number of seriously injured increased by about 15 per year, but the number of deaths is in principle unchanged. The number of seriously injured increased on all types of motorways, but the worst development was seen for narrow motorways (21.5 m wide). For 2 + 1 roads with decreased speed limit from 110 to 100 km/h, the injury accidents decreased by about 10 per year and the seriously injured decreased by about 16 per year. On 2 + 1 roads with increased speed limit from 90 to 100 km/h, the number of injury accidents increased by about 19 per year. In conclusion, the results show that in total about 17 lives per year have been saved on the road network with changed speed limits. The number of seriously injured remain in principle unchanged. It should also be noted that the results are obtained for the road network which changed the speed limits during 2008 and 2009, and it is not certain that the results can be generalised to another road network. It was predominantly roads with a low traffic safety record and unsatisfactory road sides that were selected for introduction of reduced speed limits, as well as roads with a good traffic safety record being selected for an increase in speed limits. Essentially, roads important to local economy transport and commuting have been assigned higher speed limits than roads less important from a local economy point of view. Initially, speed limit changes were introduced on approximately 3,500 kilometres of roads, out of which approximately 1,000 km were assigned an increase, and 2,500 km were assigned a reduction in speed limits. At the second stage, approximately 17,000 km were subjected to speed limit changes, out of which 1,700 km were selected for an increase and 15,000 a reduction in speed limit. The evaluation is based on accident rates from the accident data base Strada (Swedish Traffic Accident Data Acquisition) combined with information on roads from National Road database, NVDB. The study is a before and after study with control group where the change in accident and injury outcome on roads with new speed limits is compared with the corresponding change in the control group (similar roads with unchanged speed limit). Such an experimental setting controls for general traffic safety changes over time and the results therefore reflect the effect of new speed limits. (Author/publisher)
Abstract