Rumble strips have been widely used along the sides of highways to help prevent drivers from drifting off the road. A new Institute study finds that installing the same strips along the centerlines of undivided, rural two-lane roads can reduce head-on and opposing-direction sideswipes by about 20 percent.
A disproportionate number of fatal crashes occur on rural roads, and most such crashes occur on two-lane roads. A major problem on these roads involves vehicles crossing the centerlines and striking opposing traffic. Crashes like these account for about 20 percent of all fatal crashes on rural two-lane roads. Approximately 4,500 deaths occur annually in such collisions.
For the new study, researchers examined crash data for more than 200 miles of two-lane roads in seven states where experimental rumble strips were installed along the centerlines. The strips, like those used for years along roadway shoulders, consist of either raised or grooved patterns installed perpendicular to the direction of travel. The strips produce audible and tactile warnings when drivers stray from travel lanes.
Crashes at sites treated with centerline rumble strips were reduced by an estimated 14 percent overall, the researchers found. Injury crashes were reduced by about 15 percent. Head-on and opposing-direction sideswipe crashes, the main targets of this preventive measure, decreased by an estimated 21 percent, and injury crashes of the same type decreased by about 25 percent.
"Until now there have been only limited studies of the use of rumble strips on centerlines," says Richard Retting, Institute senior transportation engineer and an author of the new study. "State officials have attempted to evaluate their effects. A number of small before-and-after comparisons have shown reductions in crash rates, but this new study is the first large-scale scientific investigation of the effects of centerline rumble strips. The results should encourage highway departments to use this approach more widely on rural two-lane roads."
Researchers analyzed crash data for periods before and after the installation of centerline rumble strips in California, Colorado, Delaware, Maryland, Minnesota, Oregon, and Washington. In addition to collecting data along 210 miles of treated sites in these states, the researchers included several hundred miles of comparison sites that hadn't been treated to control for overall crash trends.
Rumble strips represent a relatively low-cost but highly effective way of reducing crashes caused by vehicles crossing centerlines, Retting concludes.