Safety Effect of Continuous Shoulder Rumble Strips on Rural Interstates in Maine

Abstract

In Maine, the first rumble strips were installed in 1994, and the Maine Department of Transportation and the Maine Turnpike Authority have now installed continuous shoulder rumble strips (CSRS) on the majority of the rural sections of the Interstate and turnpike system. There were approximately 620 freeway miles with CSRS at the end of 2004. The purpose of this study is to report on the effectiveness of these installations in preventing run-off-road (ROR) crashes. An evaluation of their effectiveness showed that CSRS reduced sleep-related ROR crashes by approximately 58%. A statistical analysis showed that there is 99.9% certainty that the typical reduction in sleep-related ROR crashes was at least 41%. Fatal crashes were reduced to a higher degree than other crashes. Dry road ROR crashes were reduced by about 43% making the cost–benefit ratio of installing CSRS on a typical Maine section at least 195. CSRS were less effective in eliminating crashes during inclement weather conditions. The overall effectiveness of CSRS installations was estimated to be a 27% reduction with respect to all ROR crashes.