The Idaho Transportation Department took the green light from lawmakers in 2014 to increase interstate speeds in rural areas from 75 to 80 miles per hour. Each year, ITD staff detail crash and speed data for the state’s transportation board.
The number of serious and fatal crashes is up, reflective of population increases and more drivers on the road. ITD traffic engineer Kevin Sablan told the board this month, the rate of those crashes is about the same as before the speed limit increase.
“I would say that the 80-mile-an-hour corridors are functioning as well as they were when it was 75, and as well as other highway segments, not only within Idaho but nationwide,” Sablan said.
Crash rates on southern and eastern Idaho’s rural interstates were significantly lower compared north Idaho’s interstate 90, which is included in the data but has a maximum speed limit of 75.
New technology could be helping to reduce crashes, Sablan said, but that notion is only anecdotal. “When you're in a lane and you start to swerve over, it'll tell you when there's a car right next to you or even when the car is approaching from behind. I can't imagine that it wouldn't help,” he said.
The data also show drivers have continued to pick up speed. The vast majority were driving about 79 miles an hour in these areas ten years ago before the speed limit increase. Now, most drivers are going 85 miles an hour, with average speeds even higher during the dry summer months.
Board members asked to see more detailed data in the future from individual interstate segments, and Sablan said the office of highway safety was also starting to research crash data for trucks in the rural high speed zones.
