Effective low noise rumble strip design and performance

The purpose of the NCHRP 15-68 Effective Low Noise Rumble Strips project was to develop and recommend a rumble strip design capable of minimizing the exterior noise that can impact residences along a roadway while producing sufficient noise and vibration inside the vehicle to alert the operator of lane departure. A review of the previous research indicated that this could best be accomplished with a rumble strip of a sinusoidal profile. Twenty sinusoidal test sites were installed in Washington State, varying the wavelength from 12 to 24 inches, the peak-to-peak amplitude from 5/16 to 1/2 inch, and the recess from 0 to 1/8 inch. Each of the test sites were evaluated using the recommended test procedure developed during Phase I of the NCHRP project, which included a primary interior noise measurement, a primary interior vibration measurement, and an exterior pass-by measurement. Based on the accepted interior noise and vibration standard of 10 dB or more difference on and off the strips and the design goal used in this research of 5 dB or less at the pass-by location, the recommended rumble strip design is a sinusoidal profile with a 15-inch wavelength, a 7/16- to 1/2-inch peak-to-peak amplitude, and a 0-inch recess.