Rumble strips are proven safety countermeasures for roadway departure crashes. They produce vibration and noise to alert drivers that they are drifting from the travel lane. Neighboring residents—contiguous to roadways with rumble strips—often complain about the noise generated by these appurtenances. This has prompted a need to simultaneously study noise mitigation and rumble strip design and application. Preliminary studies by California and Minnesota state transportation agencies indicate significant potential for sinusoidal rumble strips to provide adequate alerting noise and vibration for the driver while significantly reducing exterior noise. While NCHRP Report 641: Guidance for the Design and Application of Shoulder and Centerline Rumble Strips, showed commendable crash reductions for traditional milled rumble strips, with dimensions of approximately 7x12 inches and ½ inch depth, other designs have been used extensively by a number of state agencies to address pavement width or bicycle accommodation issues without documentation of their comparative safety effects or noise impacts. Other states are exploring the effectiveness and appropriateness of various low-noise designs (e.g., varying widths, depths, and shapes).
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, acoustical equipment and procedures, and rumble strip designs. Due to the scope of the issue, expertise from both transportation safety and noise professionals are required to study the issue. Providing state, local, and federal agencies with recommended rumble strip designs that offer adequate alerting driver feedback and reduced external noise would potentially increase their use and expand opportunities for agencies to reach safety performance goals.
The objectives of this research were to: (1) identify or design and evaluate alternative rumble strips that provide effective alerting noise and vibration within vehicles and minimize perceived external noise, while considering several variables (e.g., vehicle types, pavement types, and speed); (2) recommend low-noise rumble strip designs that accommodate all users; and (3) develop recommendations for standard testing and measurement protocols.
STATUS: The remaining tasks will be completed under NCHRP 15-68(01).