Analyzing the Effectiveness and External Noise Levels of Sinusoidal and Traditional Shoulder Rumble Strips

Shoulder rumble strips provide an effective and low-cost safety measure to prevent roadway departure crashes. Despite their reported safety benefits, they generate external noise levels that often cause noise complaints from nearby residents. To address this challenge, this study conducted field measurements to evaluate the performance of newly constructed four sinusoidal and one traditional shoulder rumble strip designs. The objective of this study is to identify and evaluate the performance of promising designs that are capable of providing adequate in-vehicle noise levels while reducing their generated external noise levels. The field measurements were conducted using a passenger car following the American Association of State Highway and Transportation Officials Statistical Isolated Pass-by method and the Society of Automotive Engineers (SAE) standard for Measurement of Interior Sound Levels of Light Vehicles. The results of the field measurements show that all the tested sinusoidal designs generated lower external noise levels than the traditional rumble strip design while providing adequate in-vehicle noise level increases to alert inattentive drivers. The results also show that the two tested sinusoidal rumble strip designs with wavelengths of 30.5 cm (12 in.) and 40.6 cm (16 in.) provided adequate in-vehicle noise level increases while generating external noise level increases that are lower than 85% and 62% of previously tested designs, respectively. These results should be useful to State Departments of Transportation and enable them to utilize these original and effective designs, especially in residential areas, to lower the external noise levels generated by shoulder rumble strips while maintaining their roadway safety benefits.