80 mph speed limit in effect on 488 miles of interstates

July 1, 2014

Motorists can now legally drive up to 80 mph on some sections of rural  interstate highway in Wyoming, resulting from action taken by the state Legislature during its 2014 session.

WYDOT crews have completed changing speed limit signs along three sections of Interstate 25, totaling 268 miles in length, as well as on three sections of I-80 (116 miles) and two sections of I-90 (104 miles). 

In approving the speed limit increase, legislators directed WYDOT to conduct a study of the three rural interstate routes to determine where a speed limit of 80 would be appropriate. Factors considered in the study were roadway characteristics, including curves, grades, width and proximity of interchanges, as well as traffic patterns,

including current average speeds, traffic volumes and proportion of commercial trucks and passenger vehicles. Also considered were safety statistics, including crash rates and relative severity of crashes in terms of numbers of fatalities and serious injuries.

The study was completed recently and presented to the Wyoming Transportation Commission during its June 19 meeting in Cheyenne.

Road sections where the 80 mph speed limit will be implemented are:80 mph speed limit map


  • North of Cheyenne to south of Douglas; 117 miles (mileposts 18-135);
  • North of Douglas to south of Casper; 44 miles (mileposts 141-185); and
  • North of Casper to south of Buffalo; 107 miles (mileposts 190-297).


  • East end of Bridger Valley to west of Green River; 34 miles (mileposts 48-82);
  • East of Rock Springs to west of Wamsutter; 55 miles (mileposts 110-165); and
  • East of Cheyenne to west of Pine Bluffs; 27 miles (mileposts 373-400).


  • East of Buffalo to west of Gillette; 64 miles (mileposts 59-123); and
  • East of Gillette to between Moorcroft and Sundance; 40 miles (mileposts 130-170).

"The safety and welfare of the motoring public is a priority to the Wyoming Highway Patrol; therefore, the 80 mph speed limit will be strictly enforced. Drivers should not count on leniency if they operate at higher speeds," Highway Patrol Administrator Col. John Butler said.

"The members of the transportation commission are pleased to see the speed limit raised and think it's a good, common sense change for our state,"  chairman Bruce McCormack of Cody said. "But it's also for all drivers to adopt an extra measure of caution in traveling at these higher speeds so that this change does not come at the cost of more traffic crashes, injuries and fatalities."

WYDOT is continuing to assess two other sections of interstate where a speed limit increase could be possible. One section, measuring 46 miles, is I-80 from west of Rawlins to just west of Walcott Junction. The other section, measuring 17 miles, is I-90 from east of Sundance to the South Dakota state line. WYDOT does not have a time frame for completing the additional study.

Going forward, WYDOT will continue to monitor those Interstate sections going to the 80 mph speed limit this summer. The results of the speed limit increase will be revisited to determine if further changes in section lengths will be warranted.

Wyoming now joins Utah and Texas as states which have speed limits above 75 mph on select rural highways. Idaho is also preparing to implement an 80 mph speed limit on some of its Interstate highways.