In response to last week’s letter to the editor, “Beware of Rumble Strips,” we would like to clarify a couple things about rumble strips and sinusoidal strips, or “mumble strips,” and why MnDOT is installing them along Minnesota highways.
Nearly two decades ago, MnDOT began installing rumble strips along highway shoulders. The purpose is to alert tired or distracted drivers they are drifting across lines, potentially causing a severe or fatal crash. They are also beneficial during winter months when snow, at times, prevents drivers from seeing the edge of the lane.
Statewide, studies have proven the strips to be highly effective. Since the implementation of rumble strips, and other safety measures, Minnesota has seen a decrease in fatalities from 625 in 2000, to less than 358 in 2017. Serious injury statistics have seen a decrease as well.
After feedback from homeowners along some of these highways – namely Highway 61 – MnDOT researched quieter rumble strips and found a new type of rumble strip called sinusoidal rumble strips, or what people refer to as mumble strips. Inside a vehicle, they provide the same sound and vibration to alert drivers they are drifting outside their lane. Outside the vehicle though, they are substantially quieter than a standard rumble strip.
Prior to last year, only “standard” rumble strips were installed along Highway 61. Last year, and moving forward, mumble strips will be installed north of Two Harbors to help keep the North Shore the oasis we all know it to be. Existing standard rumble strips will be replaced with sinusoidal rumble strips in the future when roads are scheduled for repaving.
There are six locations north of Two Harbors scheduled this summer where sinusoidal rumble strips will be installed on the shoulder. Along Highway 61, sinusoidal rumble strips will be installed outside of the white edgelines or foglines, with no plans for centerline rumble strips. Ideally, drivers should not be driving outside their lanes, and these rumble strips won’t be driven over unless in the case of a distracted driver who needs the vibrations to remind them to drive safely.
MnDOT’s goal is to provide safe transportation infrastructure for the public. Rumble strips, and now the quieter sinusoidal rumble strips, are just one of the ways we are doing that. A side benefit that has been shared with MnDOT is that drivers appreciate the rumble strips during snow-covered road conditions to let them know they are outside of the lane.
There are several locations along the North Shore that currently have sinusoidal shoulder rumble strips. These are located south of Lafayette Bluff Tunnel to Crow Creek Bridge, south of North Shore Mining Plant, and north of Palisade Head to south of Little Marais. MnDOT encourages you to get out of your vehicle and experience what these sinusoidal rumble strips sound like for yourself.
To listen for yourself, please visit our website at www.dot.state.mn.us/ d1/ to hear the difference between rumble strips, mumble strips and no strips.
Duane R. Hill, P.E.
District Engineer, MnDOT District 1
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