Rumble Strips

Roadway departure crashes account for more than half (53%) of fatal crashes each year in the United States. Rumble strips, which are milled or raised elements on the roadway, are designed primarily to mitigate crashes caused by distracted, drowsy, or otherwise inattentive drivers through vibrations and sounds made when vehicles have left the travel lane. (Federal Highway Administration, 2012).

Rumble strips can be installed on the shoulder, the edge or the centreline of roadways. Shoulder rumble strips, which significantly reduce run-off-road crashes, are installed on a shoulder near the edge of the travel lane. Edge line rumble strips are very similar to shoulder rumble strips, but are placed at the edge of the travel lane, usually in line with the edge line pavement marking. Centre line rumble strips are installed at or near the centre line of an undivided roadway, and may be comprised of either a single or double line of rumbles. They reduce cross centre line crashes such as head-on collisions and some run-off-road left crashes (Federal Highway Administration, 2012).

Torbic et al. (2009) conducted research to develop guidelines for the design and application of shoulder and centreline rumble strips as an effective motor vehicle crash reduction measure, while minimizing adverse effects for motorcyclists, cyclists, and nearby residents.

Torbic et al. (2009) indicated that shoulder rumble strips may be considered for implementation on urban and rural freeways, on- and off-ramps, multilane divided highways, multilane undivided highways, and two-lane roads. The criteria that may be considered for determining whether implementation is appropriate include shoulder width, lateral clearance, traffic volume, bicycles, pavement type, pavement depth, area type, speed limit, and crash experience. The most reliable and comprehensive estimates of the safety effectiveness of shoulder rumble strips are for freeways and rural two-lane roads.

Torbic et al. (2009) cited research results from Griffith (1999) on rolled shoulder rumble strips on urban/rural freeways that resulted in an 18% reduction in single-vehicle run-off-road (SVROR) crashes and a 13% reduction in fatal and injury producing SVROR crashes. The authors found that the installation of shoulder rumble strips on rural freeways resulted in an 11% reduction in SVROR crashes and a 16% decrease in fatal and personal injury SVROR crashes. The author’s research also demonstrated that the installation of rumble strips on two-lane rural roads resulted in a 15% reduction in SVROR crashes and a 29% decrease in fatal and injury producing crashes.

Torbic et al. (2009) also cited research results from Carrasco et al. (2004) of shoulder rumble strips installed on rural multilane divided highways, which showed a 22% decrease in SVROR crashes and a 51% reduction in fatal and injury SVROR crashes. However, the authors noted that the reliability of the effectiveness results of shoulder rumble strips on rural multilane divided highways was not as reliable as the estimates for freeways and rural two-lane roads.

The safety evaluation performed by Torbic et al. (2009) during their research found statistically significant evidence that on rural freeways, rumble strips placed closer to the edgeline were more effective in reducing SVROR fatal and injury crashes compared to rumble strips placed further from the edgeline.

Centreline rumble strips may be considered for implementation on a range of roadway types, including urban and rural multilane undivided highways and rural two-lane roads. Criteria that may be considered for determining whether implementation is appropriate include lane width, traffic volume, pavement depth, area type, speed limit, and crash experience. The most reliable and comprehensive estimates on the safety effectiveness of centreline rumble strips are for those installed on urban and rural two-lane roads. On urban two-lane roads, centreline rumble strips are estimated to be 40% effective at reducing all head-on and opposite-direction sideswipe crashes and 64% effective at reducing head-on and opposite-direction sideswipe fatal and personal injury collisions. On rural two-lane roads, centreline rumble strips are 30% effective at reducing all head-on and opposite-direction sideswipe crashes and 44% effective at reducing the same type of fatal and personal injury collisions (Torbic et al., 2009).

Srinivasan et al. (2010) examined the impact of installing transverse rumble strips at three-leg and four-leg intersections in Iowa and Minnesota on total crashes, injury crashes, and specific crash types, such as right-angle and run stop sign crashes. Transverse rumble strips are used to alert drivers of an upcoming change or hazard in the roadway or to warn drivers of needed lane changes, the need to slow down or stop, or changes in the roadway alignment. Transverse rumble strips are usually located on approaches to intersections, toll plazas, horizontal curves or in work zones. Srinivasan et al. (2010) found that following the installation of transverse rumble strips at both three- and four-leg intersections locations in Iowa and Minnesota, fatal and incapacitating injury crashes were reduced by 39% while fatal and personal injury crashes decreased by 21%.

Scope of the Problem

• Federal Highway Administration (2012) Proven Safety Countermeasures Longitudinal Rumble Strips and Stripes on 2-Lane Roads. U.S. Department of Transportation, Federal Highway Administration. Washington, D.C. Retrieved from http://safety.fhwa.dot.gov/provencountermeasures/fhwa_sa_12_008.htm

Evidence

• Torbic, D.J., Hutton, J.M., Bokenkoger, C.D., Bauer, K.M., Harwood, D.W., Gilmore, D.K.., Dunn, J.M., Ronchetto, J.J. Donnell, E.T., Sommer III, H.J., Garvey, P., Persuad, B. & Lyon, C. (2009) Guidance for the Design and Application of Shoulder and Centreline Rumble Strips. National Cooperative Highway Research Program Report 641, Transportation Research Board, Washington, D.C. Retrieved from http://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_641.pdf
• Srinivasan, R., Baek, J., & Council, F. (2010). Safety Evaluation of Transverse Rumble Strips on Approaches to Stop-Controlled Intersections in Rural Areas. Presented at 89th Annual Meeting of the Transportation Research Board, Washington, D.C. Retrieved from http://www.fhwa.dot.gov/publications/research/safety/hsis/12047/12047.pdf