Rumble Strip Types
There are four types of shoulder rumble strips. They differ primarily in how they are installed, their shape and size, and the amount of noise and vibration produced:
Highway agencies often use all types of shoulder rumble strips, depending on the need and the material. The groove pattern can be installed intermittently or continuously. The groove pattern, depth, width, shape, and spacing may also change with the road agency.
Milled Rumble Strips
Research indicates that different dimension milled rumble strips provide different amounts of sound and vibration in the passenger compartment. Tires passing over milled rumble strips drop roughly into the groove, which causes tire noise and vehicle vibration. In general the wider and deeper the rumble strip, the more sound and vibration. Recent research suggests the length of the rumble strip is not as critical as once thought, largely due to the fact that the amount of vibration and noise in large trucks is not enough above the ambient levels to alert a drowsy driver. A six-inch length appears to be adequate and some States are now experimenting with four-inch edge line rumble stripes. Typical widths are 5 to 7 inches with 12 inch spacing and approximately 0.5 inch depth.
Milled rumble strips are made by a machine with a rotary cutting head, which creates a smooth, uniform, and consistent groove into the pavement.
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.
Rolled Rumble Strips
Rolled rumble strips are rounded or V-shaped grooves pressed into hot asphalt pavements and shoulders when the constructed or reconstructed surface course is compacted. The strips are made by a roller with steel pipes welded to drums, which make the depressions as they pass over the hot pavement. The sound and vibration of rolled rumble strips is typically much less noticeable than milled rumble strips, but varies based on width, depth, and spacing.
What Do Rolled Rumble Strips Sound Like?
Autos and trucks make very different sounds on rolled rumble strips. You can download and compare the sounds in a video demonstration.
Formed Rumble Strips
Formed rumble strips mirror the rolled type in shape but are made by pressing forms into concrete shoulders as they are being constructed(32-mm-deep, 40-mm-wide rounded or V-shaped grooves).
Raised Rumble Strips
Raised rumble strips are 50- to 305-mm-wide rounded or rectangular markers or strips that adhere to new or existing pavements. Some road agencies use raised buttons. Because their height can range from 6 mm to 13 mm, use of raised rumble strips is usually restricted to warmer climates that don't require snow removal (see the Areas of Concern section).