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Increased speed limit doesn't increase speeds significantly, data shows

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MURRAY — When the Utah Department of Transportation raised the speed limit along I-15, I-215 and I-80 in December, many feared motorists would drive faster.

After more than four months with the new limit, UDOT released its preliminary data and found while many motorists are still breaking the speed limit, the average speeds haven’t changed that much.

The new speed limit is along I-15 from Spanish Fork to Ogden, on all of I-215, and on I-80 from about 5600 West to 1300 East in Sugar House. When UDOT raised the speed limit in December, part of the reasoning was that motorists were already driving 70 mph.

"People are driving the speeds that they're most comfortable driving at,” UDOT spokesman John Gleason said.

On most of the Wasatch Front, interstate means 70 mph or faster. The speed limit rose 5 mph, but the speed data UDOT released Tuesday shows the average flow of traffic did not speed up.

"By raising the speed limit from 65 (mph) to 70 (mph), we really didn't affect the speed most people were driving,” Gleason said.

That’s what UDOT expected to see.

The study found as drivers got closer to Syracuse in Davis County, the average speed was up 2 miles per hour — from 77 mph to 79 mph. Down in Lehi, it’s up 1 ½ miles per hour, approaching 80 mph.

Along I-215's west belt and on I-15 to the north and south of Salt Lake City, the average speed is more than 75 mph. But the speed did not rise significantly with the higher speed limit, Gleason said.

(Speeds have) even gone down in some areas; but for the most part, it's really remained the same.

–John Gleason, UDOT spokesman

"It's even gone down in some areas,” he said, “but for the most part, it's really remained the same."

UDOT has seen an increase in interstate fatalities, but more of those are related to not buckling up than excessive speed.

“We haven't had an increase in speed-related crashes this year,” Gleason said.

The Utah Highway Patrol initially opposed the increase but now maintains a stance of enforcing the posted limit.

UDOT wants to track the crash and speed data over several years.

“We want to set the speed limit at the appropriate level," Gleason said. “We generally like to look at trends over several years, not just a few months, just so we can have all of that information."

If UDOT safety analysts notice any substantial changes in the data in the future, they'll review the speeds again.


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Jed Boal


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