Evaluation of Safety Benefits and Potential Crash Migration Due to Shoulder Rumble Strip Installation on Connecticut Freeways

With the encouragement of FHWA, many states are installing shoulder rumble strips to reduce the number of run-off-the-road crashes. In 1996, Connecticut began full-scale installation of shoulder rumble strips on limited-access highways (freeways). This paper describes research aimed at answering three questions about the effectiveness of this project: (a) Do rumble strips reduce single-vehicle, fixed-object crashes? The analysis indicates that installing shoulder rumble strips reduces these crashes by 33%. (b) Do certain roadway factors influence the rate of these crashes with regard to the rumble strip installation locations? In the sections where rumble strips were installed, run-off-the-road crashes were reduced by as much as 48.5% in interchange areas and as little as 12.8% on sections of roadways where the speed limit was less than 65 mph. (c) Is the potential adverse effect of crash migration (from locations with rumble strips to those without) occurring? The roadway factors analyzed and sections of longer routes in Connecticut both indicate increases in run-off-the-road crashes where rumble strips are not placed, even when exposure is controlled. These findings indicate that for rumble strips to be most effective along freeways, consideration should be made for continuous installation both to reduce crashes where they are installed and to avoid increases in crash occurrence where they are not.