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Richfield • New 80 mph speed limits on Interstate 70 from the Colorado line to Cove Fort increased real speeds by only about 1 mph, the Utah Transportation Commission was told Friday.

When the speed limit was 75 mph there, typical real speeds averaged 82-83 mph for most traffic.

"Now it is 84 mph. So there's not much change," said Robert Dowell, UDOT Region 4 traffic operations engineer.

What has changed, he said, is that more traffic now travels at similar speeds, with less difference between the fastest and slowest cars.

When limits were slower, traffic that insisted on obeying speed limits often went much slower than speeders. Difference in speed is considered a major cause of accidents and fast cars come up quickly on slower traffic.

Transportation Commission member Naghi Zeenati quipped that the higher speed limits allow "most of us to drive legally at what had been illegal."

In recent years, Utah has increased speed limits to 80 mph on interstate freeways in most rural areas. The speed limit on I-70 was raised just last spring, and UDOT's Region 4 reported Friday on results. Similar results have been seen statewide for other 80 mph zones.

Dowell also said UDOT is continuing to study and rework slower recommended speeds to improve safety for some curves on I-70.

He also said Region 4, which covers southern Utah, is studying whether to increase speed limits on one final section of Interstate 15 in its area between the Arizona line and St. George.