'Mumble strips' – quieter than rumble strips – rolling out on MN roads

Minnesota's transportation leaders are rolling out a project to replace rumble strips with "mumble strips."

You've got to hand it to the Department of Transportation (MnDOT), it's a catchy name,. But MnDOT says it's also a way of solving a problem that has been plaguing residents living near busy roads.

Earlier this year, we reported how MnDOT was looking into new ways of reducing the noise made when vehicles drove over rumble strips designed to stop them veering across the centerline, after a "significant number of complaints" from homeowners who could hear them more than 3,000 feet away.

And MnDOT believes it found the answer in "sinusoidal" rumble strips, which are said to reduce the external noise made when a vehicle comes into contact with them, yet still produces a "good amount" of noise and vibration that's needed to alert the driver.

Currently, 800 miles of Minnesota roads have the traditional rectangular rumble strips. The sinusoidal strips on the other hand are shaped in a "sine wave" pattern that helps reduce external sound.

Here's a comparison of the two:

https://www.youtube.com/watch?v=W3-uPGb1nmM

Installation underway

In a news release on Thursday, the transportation department said it will commence a $5.9 million project to install the mumble strips along the centerline on Highway 42 in southeast Minnesota, between Eyota and Plainview.

The move was made in response to "external noise concerns" and will see the road closed and detoured for a month while they're installed.

MnDOT is keen to push ahead with installing the strips in several spots across the state, having settled on a preferred design.

KSTP reported last week that MnDOT crews installed the new strips on Highway 22 near Kasota, having conducted numerous tests over the summer using different-sized vehicles traveling at different speeds.

For now, only the centerlines on Highways 22 and 42 will have the mumble strips, though KSTP notes there is talk of expanding this to shoulders in the future.

The presence of rumble strips on centerlines are estimated to reduce crossover crashes by 44 percent, according to MnDOT.