Previous legislation allowed UDOT to operate several 80 mph "test areas" on I-15 between Nephi and Cedar City for the past four years. The new bill would stretch that zone from Santaquin in the north to St. George in the south.
It would also allow 80 mph zones to be placed in areas deemed safe for them on I-15 between Brigham City and the Idaho state line, on I-84 between Tremonton and Idaho, and on I-80 from the Nevada line to the Tooele-Stansbury exit.
Rep. Jim Dunnigan, R-Taylorsville, the bill's sponsor, said four years of data show that when the speed limit in test areas was just 75 mph, actual speeds averaged 82 mph. When limits were raised to 80 mph, average speeds rose only slightly to about 83 mph.
"What we accomplished was people were just legal in traveling at that speed," Dunnigan said, adding drivers seem to travel at a "natural speed limit" where they feel comfortable regardless of the posted speed limit. "Also very interesting was that there was not an increase in accident rates and no increase in fatalities."
Dunnigan and UDOT made clear that 80 mph zones would be created only in a few portions of the allowed area where engineers figure it would be safe.
UDOT Deputy Director Carlos Braceras said UDOT plans to rule out any stretches where speed has been a factor in crashes. He said it would also exclude areas where curves or hills would make such high speeds dangerous. UDOT would review speed and accident data for years, he assured, before making any new 80 mph zones permanent.
Braceras also noted that at a time when air quality has become a concern because of inversions, newer cars pollute about as much at higher speeds as at lower speeds so the higher speed limits should not increase pollution much.
"A lot of work has been done here, and data show it is safe to make these changes. I think people appreciate it. I know I do," said Rep. Johnny Anderson, R-Taylorsville.
Utah and Texas currently are the only states that have any speed limits higher than 75 mph. Most Utah freeways in rural areas have 75 mph limits, while the limit is 65 mph in urban areas.