In-Vehicle Evaluation of Milled Rumble Strips in Pre– and Post–Chip Seal Maintenance Periods

Driver fatigue and drowsiness can have a profound impact on safety. Centerline and shoulder rumble strips are popular countermeasures designed to produce audible and tactile warning when vehicles deviate from the travel lane onto the rumble strips. These warnings reduce the risk of lane departure crashes. Studies show that the noise produced by rumble strips is a function of many variables. Rumble strip depth is known to have the greatest impact in alerting drivers. However, chip seal pavement maintenance operations tend to reduce the original rumble strip design depth, which may have an impact on the functional effectiveness of the rumble strips. The purpose of this study was to conduct a controlled experiment to understand the relationship between milled rumble strip depth and noise and vibration in the vehicle cab. In-vehicle noise and vibration levels were collected on rumble strips of five depths (⅛, ¼, ⅜, ½, and ⅝ in.) and three types (shoulder, single centerline, and double centerline) on three highways in the state of Nebraska by two vehicles traveling at speeds of 45, 55, and 65 mph. Rumble strip depths at ⅛-in. intervals were used to simulate the influence of a chip seal on rumble strip effectiveness. From the in-vehicle sound and vibration levels of all the tested rumble strip depths, it can be hypothesized that a ⅛-in. reduction in the current milled rumble strip design depth, as a result of chip sealing, would not cause a practical reduction in the effectiveness of rumble strips producing audible and tactile warnings to alert drivers.