Evaluation of Audible Lane Departure Warning Treatments on Seal Coats

To help reduce single vehicle run-off-road and two-lane two-way crossover crashes, Texas Department of Transportation (TxDOT), United States, has implemented various audible lane departure warning systems on seal coat road surfaces. This 20-month research project explored the effectiveness of these treatments using interior noise and vibration 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, varying spacing of rumble bars, and milled rumble strips. Researchers found that treatment effectiveness varies with vehicle type and vehicle speed. Traveling at higher speeds and in a vehicle with a stiffer suspension results in higher noise and vibration levels. The specific treatment design also impacts the performance. Treatments with closer spacing, longer bumps, and higher profiles produced higher noise and vibration levels. Certain alternative treatments were able to produce noise and vibration levels that approached levels of typical milled rumble strips. In areas where milled rumble strips cannot be used, these alternative treatments are viable options.