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Speed limit on section of U.S. 20 increases to 70 mph Wednesday


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U.S. Highway 20 near Thornton | Idaho Transportation Department

The following is a news release from the Idaho Transportation Department.

RIGBY – The speed limit on U.S. Highway 20 between Idaho Falls and Ashton will increase to 70 mph Wednesday, for both passenger vehicle traffic and commercial trucks.

The speed-limit changes stem from engineering and traffic studies completed Feb. 21 for the 50-mile stretch of U.S. 20. Results indicate that 85 percent of drivers travel the route at 70 mph or below. Setting speed limits according to this “85th-percentile speed” results in the lowest crash rates.

Idaho Transportation Department (ITD) officials discussed the proposed speed-limit increases with county officials and law enforcement prior to formalizing the changes.

The current 65-mph speed limit remains in effect until the new 70-mph signs are posted. Motorists should take extra care while highway crews change signs along the route. Idaho State Police and local law enforcement officers will patrol the road during and after the speed-limit transition.

ITD officials recommended the changes to the Idaho Transportation Board and received approval March 16.

“Raising the speed limit to 70 mph will further traffic safety and mobility,” said District 6 Traffic Engineer Ben Burke. “Posted speed limits can’t replace common sense, however. Drivers should always slow down if necessary to meet hazardous conditions.”

Speed limits are the maximum speed motorists can legally travel under ideal roadway and weather conditions. Limits encourage better traffic flow by reducing the variances in speed from one vehicle to the next.

Crews also will adjust the speed limits on each side of the stretch of U.S. 20 for improved transitions. For instance, the speed limit between Lindsay Boulevard and Riverside Drive in Idaho Falls will be lowered from 55 to 45 mph. See the speed-limit map here for more details.

The Idaho Transportation Department uses traffic studies to determine what speed motorists consider reasonable, convenient and safe for existing driving conditions. Speed limits are intended to supplement driver judgment and are set at a level that studies indicate drivers will adhere to voluntarily.

In 2014, the Idaho Legislature amended the “Basic Rule and Maximum Speed Limits” in Idaho Code to allow the Idaho Transportation Board to raise interstate speed limits to 80 mph and other state highway speed limits to 70 mph, when concluding that the increases are in the public interest based on engineering and traffic studies.

Last year, ITD raised the speed limit to 70 mph on U.S. 20 between Idaho Falls and Butte City, on Idaho 22 between its junction with Idaho 33 and Dubois, and on Idaho 28 between Mud Lake and Leadore. The transportation department also raised the speed limit to 70 mph on a 15-mile section of U.S. 95 in northern Idaho.