Evaluation of Sinusoidal Rumble Strips on Noise Mitigation and Roadway Departure Crash Reduction

Lane departure crashes are among the most common crashes in Florida and in the USA, and preventing those crashes is the priority of many departments of transportations (DOTs) across the nation. Auditory Vibratory Treatments (AVTs), or rumble strips, are frequently used to prevent or reduce lane departure incidents. Traditional cylindrical ground-in and profiled thermoplastic rumble strips produce exterior noises that become a burden to nearby residents. In consideration of noise issues, a few DOTs, including the Florida Department of Transportation (FDOT), have been considering a new type of AVT called sinusoidal rumble strips. Based on an FDOT research project, this paper evaluated the noise reduction and safety effectiveness of sinusoidal rumble strips in Florida and in other states with respect to their abilities to reduce exterior noise, properly alert drivers, and enhance safety. Researchers conducted 1) a comprehensive literature review, 2) agency interviews, 3) sinusoidal rumble strip noise studies, and 4) a safety evaluation of sinusoidal rumble strips via before-after crash analysis to assess both noise reduction and safety effectiveness of sinusoidal rumble strips.

For the noise reduction evaluation, the results from the comprehensive literature review and five state agency interviews confirmed and recognized that sinusoidal rumble strips were the most effective rumble strips to reduce exterior noises. Based on the FDOT Material Office noise study, and the focus group noise study by the Center for Urban Transportation Research (CUTR) at the University of South Florida (USF), the FDOT Type 2 sinusoidal rumble strip design was the best among three FDOT designs to reduce exterior noise and alert drivers via combined interior noises and vibrations. For the safety analysis, the roadway departure crashes before and after the implementations of sinusoidal rumble strips at 12 study sites and 12 control sites in Florida were collected, compared, and analyzed. An Empirical Bayes (EB) approach was used to develop Crash Modification Factors (CMFs) and a multinomial logit model was applied to assess the influence of sinusoidal rumble strip presence on lane departure crash severity. The safety evaluation results showed that, considering all crashes, sinusoidal rumble strips were found to reduce total lane departure crashes by 57% (CMF=0.43) overall, 30% (CMF=0.70) for rural two-lane roadways, and 61% (CMF=0.39) for rural multi-lane roadways. Furthermore, they can significantly reduce lane departure crash severity.  

Researchers concluded that sinusoidal rumble strips are an effective safety countermeasure to lower exterior noise, address noise issues, properly alert drivers, and significantly reduce lane departure crashes and their severities. Transportation agencies can implement sinusoidal rumble strips to address the exterior noise issues and significantly reduce roadway departure fatalities, serious injuries, and crashes.