LANSING, MI — Residents of Macomb County have not heard the latest “mumbling” on their county roads because the quieter sinusoidal rumble strips — a.k.a. mumble strips — are taking the place of traditional rumble strips technology.

Rumble strips on the edge and centerlines of roads and highways have been around for years. They are used to keep drivers alert and prevent head-on and run-off crashes. Mumble strips function like rumble strips except they produce less noise.

The Macomb County Department of Roads (MCDR) is one of the first road agencies in Michigan to use the new technology, on almost 100 miles of two-lane roads in its northern, more rural areas.

“With sinusoidal, your tires still bump down and up, but less abruptly,” said Mia Silver, MCDR Project Engineer. “It’s quieter outside the vehicle and it’s also quieter inside the vehicle, but it is still loud enough inside the vehicle to provide effective feedback to the driver.”

This new technology is featured in the Fall 2019 edition of Crossroads, the quarterly journal of the County Road Association (CRA) of Michigan.

In addition to driver safety and alertness, mumble strips also improve the visibility of a road’s centerline significantly, especially in wet conditions. This is due to the strips’ waved surface pattern. MCDR hopes this quiet innovation — funded with a grant from the Michigan Department of Transportation — will reduce the number of crashes and fatalities in the county. In 2014, Macomb County experienced 24,471 crashes and 41 fatalities. By 2018, that number had risen to 25,784 crashes and 52 fatalities.

“Macomb was looking for applications, technologies that can help with run-off-road or head-on crashes on two-lane roadways,” said John Abraham, Ph.D., PE, PTOE, Director of Traffic and Operations for MCDR. “We conducted thorough research on sinusoidal, looked at the design elements and talked to our partners at MDOT who were also looking at this application. We came to a consensus that this could work for us.”

The 83 members of the County Road Association of Michigan represent the unified voice for a safe and efficient county transportation infrastructure system in Michigan, including appropriate stewardship of the public’s right-of-way in rural and urban Michigan. Collectively, Michigan’s county road agencies manage 75 percent of all roads in the state, including 90,000 miles of roads and 5,700 bridges. County road agencies also maintain the state’s highway system in 64 counties.