Utah now has two stretches of 80 mph freeway, the highest speed limit in the Intermountain West -- and probably the West's largest speed trap in between. While Utahns relish being unique in some ways -- redrock wonders and the Best Snow on Earth come to mind -- the fastest traffic in the West isn't something to boast about.

The Legislature last year approved a bill allowing the Utah Department of Transportation to raise the speed limit on sections of rural freeway above 75 mph and requiring the department to study the results and issue a report. The assumption is that if accidents don't increase on these 18- and 19-mile stretches of I-15 -- one between Mills Junction and Scipio and the other from Fillmore to just south of Kanosh -- the speed limit would be raised all along the interstate from Nephi to Cedar City.

That would be dangerous for drivers and bad for the environment.

Raising the speed limit by 5 mph would not radically change the speed that most responsible drivers drive. Studies show that most people drive near the posted speed if highway conditions allow. But those 80 mph speed signs could encourage the irresponsible drivers who already are a danger to others to exceed the speed limit by much more than 5 mph.

Another reason to encourage a moderate speed is the air pollution caused by going faster. Increasing speed by 5 mph cuts fuel economy by about 6 percent. Using more fuel puts more emissions into the air.

The yearlong experiment creates a section of about 20 miles between the two 80 mph sections, a literal speed trap for those who up their cruise controls and then forget to drop their speeds back to 75 before resetting them to 80, and then back to 75. Although this roller coaster might help some diligent drivers stay alert just to keep up with the changes, it is a bit unfair to those who get ticketed in the no-man's-land between higher-speed sections.

Utah is already at the high end of the spectrum in speed limits. In the West, only Texas has an 80 mph limit for cars, and only during daylight hours. Other Western states' rural interstate speed limits are uniformly 75 mph, the same as Utah's.

We understand wanting to travel the 155-mile stretch of sameness between Cedar City and Nephi as quickly as possible. But arriving a few minutes earlier isn't worth a tradeoff in dirtier air or even one more fatality.