Effectiveness and acceptability of milled rumble strips on rural two-lane roads in Sweden

Purpose The study sought to estimate the effects of centreline milled rumble strips on rural two-lane roads in Sweden in a wide perspective. Traffic safety effects (i.e., fewer crashes and injuries), driver experience, and driver opinions of centreline milled rumble strip usage on rural roads are investigated. Methods To evaluate the traffic safety effects, an Empirical Bayes study comparing the outcome before and-after the introduction of rumble strips was conducted. This study is based on data from 2003–2012 from the Swedish national traffic accident database, STRADA. To capture driver experience and opinions about milled centreline rumble strips, focus groups and road-side interviews were performed. Results The results indicate a significant decrease in all types of severe injury crashes, a 20% (±13%) reduction in the number of fatalities and seriously injured people (all crash types) and a 27% (±18%) reduction in the number of fatalities and severely injured people in single-vehicle crashes. Participants in focus groups and road-side interviews generally favoured centreline rumble strips on rural roads, and up to 90% of the interviewed motorcyclists and commuters stated that the rumble strips would help improve traffic safety. Conclusions Rumble strips in the centre of two-lane rural roads are a countermeasure to help drivers who are unintentionally about to leave the lane, for example, due to sleepiness or inattention. Based on the results of this study, installing centreline milled rumble strips on two-lane rural roads 8–10 meters wide is a measure to consider to increase safety.