Exploring the Safety Impacts of Rumble Strips on Prevention of Lane Departure Crashes

Enhancing safety of roadway segments is a critical step towards maintaining durable transportation infrastructures. Due to significant costs associated with construction of roadway segments, redesigning or rebuilding a roadway segment is not always a viable solution for safety improvement. Low-cost safety countermeasures are effective tools to enhance safety while diminishing reconstruction costs. Among all traffic collisions, the lane departure crashes continue to be the leading type of serious traffic accidents in Maine, comprising 70% of state-wide traffic fatalities [Maine HSIP Annual Report, 2018]. Installations of shoulder and centerline rumble strips have been a primary countermeasure to prevent lane departure crashes in Maine. For instance, from 2015 to 2017, centerline rumble strips have been installed on over 415 miles of roadways in Maine. In addition, from 2018, Maine DOT started installing sinusoidal rumble strips; although studies reported noise reductions compared to traditional rumble strips, little is known about safety impact of sinusoidal rumble strips compared to the traditional ones. With an increased demand in rumble strip installations, there is a clear DOT, industry and agency need to understand the impact of rumble strips in mitigating lane departure crashes in Maine for different road types. This project will employ Empirical Bayes (EB) observational before-after study (and/or other statistical tools when appropriate) to explore the effectiveness of rumble strips in Maine and develop state-specific crash modification factors (CMFs). The evaluation will investigate the impact of both centerline and shoulder rumble strips on reducing the frequency and severity (Fatal, Injury and PDO) of lane departure crashes (e.g.: run-off the road and head-on collisions) on select roadway types (e.g.: rural two lane roads) under different conditions. The proposed study will also use benefit-cost analysis to explore the economic benefits of using rumble strips.