The idea behind rumble strips, that is both shoulder rumble strips and median rumble strips, is to “awaken/alert” the driver who is involuntarily intersecting the median or side lane marker, and to thereby prevent single-vehicle accidents and multi-vehicle collisions. This report presents the results from the studies conducted by VTI (Swedish National Road and Transport Research Institute) as part of the Swedish Transport Administration’s Safe Accessibility development programme from 2007 – 2012. With respect to shoulder rumble strips on motorways, the results show that the total number of deaths and severe injuries on motorways with a 110 km/h speed limit has decreased by 17 per cent, and by roughly 30 per cent for single-vehicle accidents. Numerous studies have been conducted on the various effects of median milled rumble strips on two-lane roads. Results from accident analyses show that the number of deaths and severe injuries has decreased by roughly 6 per cent. The corresponding decrease for single-vehicle accidents is 14 per cent. These results are significant. Analyses of accident processes based on police reports indicate that median rumble strips reduce the risk of multi-vehicle collisions and accidents in which a driver drives leftward off the road. Simulator studies show that rumble strips are effective in awakening tired drivers, and that drivers who are awakened by rumble strips take the proper countermeasures. Speed measurements show no clear changes in terms of average speed after median rumble strips have been installed. With regard to lateral positioning, the results show that cars travel roughly 5 centimeters away from the centre line and that the variance of lateral position decreases slightly. This might lead to an increased rutting and wear. In the driver interviews that were conducted, 90 per cent of the drivers considered that median rumble strips contribute to higher traffic safety. Truck drivers are also positively disposed, although they advocate deeper strips. In the case of divided roads (painted 2+1 with median rumble strips and speed limit 90 km/h), the number of deaths and severe injuries decreased by roughly 30 per cent. This change is not significant. These results are of the same order of magnitude as previous Swedish and German results. The results for roads with oncoming traffic separation and median barriers (sparse 2+1 roads) show that the number of deaths and severe injuries in total is 50 per cent. The change is significant, although the accident material is still too small, with the result that continued follow-up is recommended to obtain more reliable results. (Author/publisher)
Abstract