ST. PAUL - Speed limits on most rural, two-lane highways in Minnesota are increasing from 55 mph to 60 mph.

And yes, it’s safe, state officials say, following a five-year study.

The increased speed limit on some 5,240 miles of state highways — that’s 77 percent of state two-laners — is effective as soon as signs go up. In fact, many are already up, and installations will continue through the spring, according to the Minnesota Department of Transportation.

In 2014, the Legislature directed MNDOT to study whether speed limits could be safely increased. That study just finished, concluding that it is safe for most stretches of road.

MNDOT wasn’t actually required to increase the speed limit — the measure passed by lawmakers said the transportation commissioner “may” increase them.

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But once traffic engineers looked at the data, it became clear that on many stretches of these roads, folks were already driving like the speed limit was 60, and doing so safely.

How can this be safe?

It turns out everyone was already speeding anyway.

The study, which examined 68 locations on highways where the same change was made years before, found that increasing the speed limit from 55 to 60 wouldn’t actually change how folks drive a whole lot.

When the signs said 55, the average speed for all vehicles was 59 mph, and 85 percent of vehicles were going 65 mph or slower.

When the limit was upped to 60, the average speed went up to … 60. And 85 percent of the drivers still went 65 or slower.

The average of the five highest speeds — a way to measure the behavior of lead-footed drivers — was the same before and after, at 76 mph.

Before speed limit changeAfter change
85th percentile speed65 mph65 mph
Mean speed59 mph60 mph
Standard deviation6.4 mph6.1 mph
Avg of five highest speeds76 mph76 mph
*Analysis of 46 randomly selected locations 

One change that could benefit safety: The typical difference between speeds of vehicles went down slightly, according to the study, which cost $1.2 million.

“In other words, more drivers traveled at a similar speed after speed limits increased,” said Nathan Drews, engineering specialist in MNDOT’s office of traffic engineering. “This is a desirable outcome, but this change is very slight and may not affect the frequency or severity of crashes.”

Which roads?

Too many roads to list here are affected. If you’re really curious, pore over the tables on Page 24.

According to MNDOT, this is the “largest system-wide change in Minnesota speed limits since the national maximum speed limit of 55 mph was included in President Nixon’s Emergency Highway Conservation Act bill in 1974. The Minnesota Commissioner of Highways later that year established an executive order about speed limits.”