Rumble strips alert sleepy and inattentive motorists that they are about to veer off the highway or into the opposite lane of traffic. But the grating noise that prevents collisions can also be annoying to nearby residents.
Around Minnesota, more and more counties are facing push-back as they install shoulder rumble strips on roadways in populated areas. This is because county road shoulders are narrow — leading drivers to frequently hit the rumbles.
“There is a strong concern statewide that these noise complaints will raise enough concern that legislation may be passed reducing their use,” said technical liaison Ken Johnson of MnDOT’s Office of Traffic, Safety and Technology.
A European-developed style of rumble strip, called sinusoidal, could provide Minnesota a new means of warning drivers without as much stray highway noise.
Rumble strips are patterns ground into asphalt that cause a vehicle to vibrate when its tires come close to the centerline or road edge. They help prevent lane departure crashes, which account for more than 50-percent of fatalities on the road system.
The sinusoidal rumble (below) has a sine wave pattern ground into the pavement, while the traditional rumble strip (top photo) doesn’t follow a wave pattern.
MnDOT’s Office of Traffic, Safety and Technology plans to test different designs of the Sinusoidal rumble strips to find the one with the highest level of interior vehicle noise and lowest level of exterior vehicle noise.
The navigability of sinusoidal rumbles by motorcycles and bicycles will also be evaluated. The project was recently funded with a research implementation grant from MnDOT’s Transportation Research Innovation Group.
If sinusoidal rumble strips are found to be effective, the chosen design will be used for centerlines and road shoulders in noise-sensitive areas throughout the state highway system. It is anticipated that counties will also adopt the design.
Unlike counties, most of MnDOT’s recent complaints have been for its centerline rumbles, which are required on all rural, high-speed undivided roads in Minnesota, Johnson said.
MnDOT has considered allowing more exceptions due to residential noise concern; however, doing so could result in more fatal and serious crashes. Sinusoidal rumbles are seen as a possible alternative for these noise-sensitive areas.
The Local Road Research Board is also studying different designs of sinusoidal rumble strips in Polk County.