Milled Rumble Strips
Milled rumble strips are the current favorite type of rumble strip among many States because they are easy to implement on new or existing asphalt and Portland cement concrete pavements and shoulders; they have little or no effect on the integrity of the pavement structure; and they produce greater noise and vibration than rolled or formed rumble strips.
Milled rumble strips are generally installed with a longitudinal width of 180 mm and a transverse width of 400 mm while offset from the travel lane, typically at 300-400 mm. Tires passing over milled rumble strips drop roughly 13 mm into the groove, which causes tire noise and vehicle vibration. Field tests demonstrate that the noise and vibration from milled rumble strips are particularly effective in warning large trucks that leave the road. One study determined the effect of the milled strip to be 12.6 times rougher and 3.4 times louder than that of the rolled rumble strip.
Milled rumble strips are made by a machine with a rotary cutting head (generally with a 300 mm radius), which creates a smooth, uniform, and consistent 13-mm groove into the road shoulder.
Policy, Specifications and Drawings
In order to see how some States are implementing rumble strips on their roadways, we have provided policy, specifications and some engineering drawings in Adobe PDF format for your perusal.
Milled Rumble Strip Policy Specifications and Drawings
What Do Milled Rumble Strips Sound Like?
Autos and trucks make very different sounds on milled rumble strips. You can download and compare the sights and sounds in a video demonstration.
What Do the Experts Say?
Please note: These links will take you to QuickTime movies - they are large files (1.9 and 1.1Mb) and may take a long time to download, depending on your modem speed and Internet traffic. You will also need to have QuickTime installed on your computer to view the movies.
Emmett McDevitt, Federal Highway Administration discusses the effectiveness of milled vs. rolled rumble strips.
Peter Gustafson, New York State Thruway, talks about the use of milled and rolled rumble strips on the Thruway.
