Roadway departure crashes accounted for 18,275 fatal crashes in 2017 across the United States (Jones et al. 2017). Rumble strips (RS) provide audible and haptic interior alert when a vehicle is departing the roadway reducing run-off-the road crashes. Although inexpensive to install, and easy to maintain, RS are not installed on many roadways due to noise concerns. This Dissertation evaluated using a shallower sinusoidal RS as a quieter alternative to rounded milled RS. Rumble strip strikes by the passenger car and van generated less exterior noise with the sinusoidal than with the rounded design.
To be an effective safety countermeasure, the RS must generate an interior alert, through an increase in the interior noise and haptic feedback. The sinusoidal and rounded RS do generate a sufficient interior sound alert across passenger vehicles. The radio and climate control were tested, showing that these typical ambient conditions did increase the ambient interior noise reducing the interior alert to only a detectable level. The haptic feedback during all strikes generated a sufficient amount of vibration for all vehicle types. The heavy vehicle bridged its dual-tires over the narrower rounded RS, while the wider sinusoidal RS generated sufficient interior alert. Quieter sinusoidal RS installed in more locations extends the benefits of this safety countermeasure reducing roadway departure crashes.
The feasibility of using shallower epoxy-filled transverse rumble strips (TRS) as a quieter alternative for traditional TRS was also evaluated. Compared to the traditional TRS, the shallower epoxy filled TRS had a detectable reduction in roadside noise during probe vehicle strikes. Paving over the TRS clearly reduces roadside noise, but does not provide any driver alert.