Interstates to get 80 mph speed limit

Speed limits are set to increase on interstates throughout southern Idaho next week despite red flags raised by highway safety advocates.

On July 1 and 2, crews will work to post new signs on interstates 15, 84 and 86, upping the limit from 75 mph to 80 mph for passenger vehicles. Trucks will be limited to 70 mph, up from 65 mph.

Posted 75 mph speed limits remain in effect until signs have been replaced, said Idaho Transportation Department spokesman Nathan Jerke.

“The last sign you see is an effective speed limit that you are required to drive,” Jerke said.

But AAA Idaho raised protests over the move, which it expected to come much later this year. The organization questioned how the Transportation Department could have completed necessary studies to ensure driver safety in the three months since the bill authorizing the higher speed limit became law.

“AAA is unaware how the state system could have been analyzed so completely in such a short time,” the organization said in a news release. “AAA is concerned that the rapid switchover itself could pose safety risks for highway users. AAA is also deeply concerned about the process and will look into the matter.”

Jerke said the studies had been completed quickly because the Transportation Department used automatic traffic counters on the interstates to compile data.

“All that had to be done (was for) it to be pulled up and categorized. … For the most part the automatic traffic counters did most of the work for them,” Jerke said.

Jerke said the Transportation Department also reviewed three to five years of accident history on stretches of the interstates. It also reviewed roadway geometry.

“In just about every instance, 80 mph was a safe speed. In a couple of locations, (the Transportation Department) will be looking at posting some advisory speed limits,” Jerke said.

The change was enabled by a bill sponsored by Majority Leader Bart Davis that passed the Senate handily, squeaked through the House and was signed into law by Gov. C.L. “Butch” Otter on March 18. It sets the state’s maximum speed limit at 80 mph, making it one of only four states to allow that level of speed on highways.

Speed limits can only be increased once the Department of Transportation has completed necessary traffic studies under the law’s provisions.

Davis said the law purposefully increased only the maximum speed limit. Decisions concerning individual roads were left to the department’s technical staff, who considered such factors as hills, curves, pedestrian use, and business and residential access.

“We tried to take the politics out of it,” Davis said.

AAA raised concerns about the bill during this year’s legislative session.

“AAA was assured that no speed changes would occur absent traffic pertinent impact studies for individual road segments …,” the organization said. “The assurance from sponsors and legislative sponsors that site-specific studies would be completed before any speed changes would occur was obviously intended to assuage our concerns relative to vehicle counts, congestion, weather and other factors.”

Traffic studies of the interstate system have largely been completed, Department of Transportation officials said.

“The new speed limit is appropriate for safety and traffic flow,” said Chief Operations Officer Jim Carpenter in a news release. “Analysis of crash data, existing speed studies and the rural nature of these sections of highway all factored heavily in making these changes.”

Studies are ongoing for Interstate 90, which passes through the state’s panhandle, and for state highways, said Jerke.

Certain areas of interstate near Idaho Falls, Pocatello and in the Treasure Valley will not be increased. These include areas on interstates near Idaho Falls and Pocatello have 65 mph limits, Jerke said.

Jerke said studies showed more than 85 percent of drivers already were exceeding the posted speed limit in the areas to be increased.

Next week’s action will be the first time speed limits have been increased in Idaho since 1996.