In Utah the maximum speed limit on most Interstate highways is 80 mph (129 km/h) rural and urban is 70 mph (113 km/h). The minimum speed limit is 45 mph (72 km/h) on Interstate Highways when conditions allow.
Although 80 mph (129 km/h) is posted on most interstates, some stretches of I-80 and I-84 are posted at 70 mph (113 km/h) east of Salt Lake City. I-80 is briefly posted 65 mph (105 km/h)/truck speed and 55 mph (89 km/h) between US 40 and Wanship. Speed limit from Ogden to Spanish Fork on I-15 is 70 mph (113 km/h). The speed limit in Nephi is 80 mph (129 km/h), even though Nephi is an urban area. The Legacy Parkway, running between North Salt Lake and Farmington, has posted speed limits of 55 mph (89 km/h) along its entire length due to environmental concerns at the time of its construction.
Utah Department of Transportation raised the speed limit to 80 mph (129 km/h) on an additional 289 miles of rural interstate, including I-80 from Nevada to mile marker 99, I-84 from Idaho to I-15, and additional sections of I-15.