Nebraska LTAP


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Tufuor, E., Rilett, L., LeFrois, C. "In-Vehicle Evaluation of Milled Rumble Strips at Pre- and Post-Chip Sealed Maintenance Periods" (2017) Nebraska Department of Roads Research Report


Driver fatigue and drowsiness can have a profound impact on safety. Centerline and shoulder rumble strips (RS) are popular countermeasures designed to produce audible and tactile warning when vehicles deviate from the travel lane onto the RS. This reduces the risk of lane departure crashes. Studies show that the noise produced by RS is a function of many variables. RS depth is known to have the greatest impact on alerting drivers. However, chip-seal pavement maintenance operations have the tendency to reduce the original RS design depth, which may have an impact on the functional effectiveness of the RS. The purpose of this paper is to conduct a controlled experiment to understand the relationship between milled RS depth and noise and vibration in the vehicle cab. In-vehicle noise and vibration levels were collected on five different RS depths (i.e., 1/8", 1/4", 3/8", 1/2" and 5/8"), on three RS types (i.e., shoulder, single centerline, and double centerline), on three highways in the state of Nebraska, and using two vehicles travelling at speeds of 45 mph, 55 mph, and 65 mph. RS depths at 1/8" intervals were used to simulate the influence of a chip-seal on the RS effectiveness. On the basis of the in-vehicle sound and vibration levels of all the tested RS depths, it was shown in this research that a 1/8" reduction in the current milled RS design depth, as a result of chip-sealing, does not result in a practical reduction in the RS effectiveness at producing audible and tactile warnings to alert drivers. Re-milling of rumble strips after chip sealing is therefore not recommended if the chip seal reduced the rumble strip depth by 1/8".