MnDOT says top speed will be raised from 55 to 60 miles per hour on 5,240 miles of state highway, or 77 percent of the 7,000 miles of rural two-lane highways studied.

GOLDEN VALLEY, Minn. — Speed limits will be raised on more than 5,000 miles of Minnesota highway following a five-year study by the Minnesota Department of Transportation (MnDOT).

MnDOT says top speed will be raised from 55 to 60 miles per hour on 5,240 miles of state highway, or 77 percent of the 7,000 miles of rural two-lane highways studied. Those new speeds will go into effect when signs are posted, which MnDOT expects will be completed by spring of 2019.

The State Legislature mandated in 2014 that MnDOT conduct the $1.2M study, which is called the most comprehensive study the agency has made in terms of miles and level of detail. Researchers collected travel speed samples on each section of roadway and evaluated roadway geometrics and hazards to determine if a speed limit could be changed without affecting driver safety.

MnDOT has conducted before-and-after studies on a number of roadways that have already increased from 55 to 60 mph. Researchers found there was no change in the overall 85th percentile speed from before the speed limit change to after. The mean speed (the average speed of all drivers) increased by just one mile per hour and the standard deviation, which is the measure of how spread out the speed of all drivers was, actually reduced slightly.

“This means that after speed limits increased, travel speeds at the locations sampled were slightly more consistent between each vehicle,” said Nathan Drews, engineering specialist in the Office of Traffic Engineering. “In other words, more drivers traveled at a similar speed after speed limits increased. This is a desirable outcome, but this change is very slight and may not affect the frequency or severity of crashes.”

Drews says a properly selected speed limit can potentially increase the safety of a roadway by creating more uniform travel speeds for all vehicles.

MnDOT plans to study the effect of the changes over the next several years to ensure these roadways continue to operate safely.