Use of Both Centerline and Shoulder Rumble Strips on High-Speed Two-Lane Rural Roadways: Impact on Lateral Lane Position and Passing Maneuvers of Vehicles

A before-and-after field evaluation assessed the impacts that centerline and shoulder rumble strips on rural two-lane roadways have on various characteristics of driver behavior. The following characteristics were assessed as part of this evaluation: passing maneuvers, lateral lane placement, and centerline and edgeline encroachments. The data were collected with video cameras temporarily installed at 18 passing zones and 12 curves on rural two-lane roadways throughout Michigan. The cameras were installed at the same locations before and after the installation of rumble strips. A manual review of the videos was performed to assess the various behavioral characteristics. Nearly 78,000 vehicles were observed during review of the passing zone videos, and more than 50,000 vehicles were observed during review of the curve videos. Centerline rumble strips were found to improve driver central lane positioning tendencies and decrease the occurrence of centerline encroachments. The inclusion of shoulder rumble strips in addition to centerline rumble strips provided incremental improvements in central lane positioning and reduced edgeline encroachments. Most notable, centerline and shoulder rumble strips greatly reduced the occurrence of drivers laterally shifting to the inside while maneuvering through curves (i.e., corner cutting). In addition, centerline rumble strips did not reduce the rate of passing maneuvers. Collectively, these results suggest that both centerline and shoulder rumble strips have a positive impact on surrogate measures for roadway safety and do not negatively affect driver behavior.