Evaluation of Audible Lane Departure Warning Treatments for Seal Coat Road Surfaces

Wednesday, August 28, 2019 - 18:30

In an effort to reduce the number of single vehicle run-off-road and two-lane two-way crossover crashes, TxDOT has implemented various audible lane departure warning systems on seal coat road surfaces. This 20-month research project explored the effectiveness of these various treatments using several performance metrics and provided recommendations on implementation of these types of treatments. The researchers conducted performance evaluations at 24 unique field sites that had 51 treatments, and at a test deck that had 12 different variations of audible markings. The field sites consisted of varying designs and spacing of audible markings, rumble bars, and milled rumble strips. A crash study was conducted that considered 77 treatment sites and appropriate comparison sites. The field performance study found that the performance was somewhat variable, but the alternative treatments could produce noise and vibration levels similar to milled rumble strips. The crash study showed that the installed treatments reduced total crashes by about 19 percent across all the sites considered (30 percent reduction in fatal and injury crashes). These sites had a minimum of at least one treatment on either the edge line or the center line. Audible markings and rumble bars are viable alternative lane departure warning treatments from a noise and vibration performance standpoint, from a crash reduction standpoint, and a benefit-cost ratio (at least 11:1) standpoint. Recommendations to improve standards and specifications, and how to implement these treatments were provided. The entire study is available online at https://static.tti.tamu.edu/tti.tamu.edu/documents/0-6888-R1.pdf