Preliminary studies by Caltrans and Minnesota DOT indicate significant potential of sinusoidal rumble strips to provide adequate alerting noise while significantly reducing exterior noise. Other designs have been placed extensively by a number of state agencies to address noise, pavement width, or bicycle accommodation issues without documented studies of their comparative safety effects or noise concerns. Other states are interested and have begun exploring the effectiveness and appropriateness of sinusoidal designs. Unfortunately, noise is a very complex issue, and very few state DOTs have appropriate expertise to adequately understand and analyze the complexities of the trade-offs. Likewise, evaluation of safety performance requires a clear understanding of the traffic safety issues and appropriate statistical expertise to understand the complexity of analysis. While there have been a few independent studies of the noise associated with various rumble strip designs, they are difficult to compare because they use different vehicle types, different acoustical equipment and procedures, and have studied different rumble strip designs. Due to the scope of the issue, expertise from both traffic safety and noise professionals is required to answer the outstanding issues. State, local, and federal agencies need definitive answers at a national level on design alternatives to alert drivers that they are drifting from the lane while producing minimal additional road noise from incidental hits. If possible, a model should be developed that could be used for future rumble strip designs and different vehicle types. This would reduce the cost and effort of additional studies by individual agencies.
The objectives of this research are to: (1) conduct field testing of alternative rumble strip designs that can maximize the alerting noise and vibration within vehicles while minimizing external noise increases, accounting for the primary vehicle types within the current fleet and major pavement types, and (2) develop a modeling procedure to allow future rumble strip designs to be analyzed with minimal need for field testing.
Providing state, local, and federal agencies with recommended rumble strip designs that provide adequate alerting stimuli and little to no external noise would greatly expand the opportunities for agencies to reach safety performance goals by continued reductions in roadway departure crashes that account for over half of all traffic fatalities in the United States. Additional benefits may be seen in the future as safety and environmental professionals work hand-in-hand to solve problems together with win-win results.