Idaho drivers will see the first change to interstate speed limits in nearly two decades beginning July 1 with an increase on most rural stretches of interstate across Southern Idaho.
For the majority of interstates 15, 84, and 86, the speed limit will increase to 80 mph for vehicle traffic and 70 mph for trucks, Idaho Transportation Department announced Monday. The speed limit in the urban areas of the Treasure Valley, between Caldwell and Boise, as well as through Pocatello and Idaho Falls, will remain at 65 mph.
There are no changes to the 65-mph speed limit on Interstate 90 through northern Idaho at this time.
ITD will begin replacing speed limit signs on July 1. Some areas of interstate could be delayed until July 2, depending on the pace of work or other impacts such as weather.
The increased speed limit does not take effect until the signs are posted on each section of roadway. The 75-mph speed limit signs remain enforceable until replaced. The 80-mph speed limit will be legally enforceable immediately upon posting.
This is the first statewide increase to the interstate speed limit since an increase from 65 to 75 mph in 1996. The speed limit was raised from 55 mph to 65 mph in the 1980s.
The increased speed limit, approved by the Idaho Legislature this year, increases the maximum speed limits on interstate highways to 80 mph for vehicles and 70 mph for trucks as deemed appropriate by ITD.
Under the new law, which goes into effect July 1, the 80-mph speed limit is authorized if the department completes an engineering and traffic study on the interstate highway and concludes that the increase is in the public interest.
"The new speed limit is appropriate for safety and traffic flow," said ITD Chief Operations Officer Jim Carpenter in a press release. Analysis of crash data, existing speed studies and the rural nature of these sections of highway all factored heavily in making these changes.
The revised speed limit law also allowed for speed limit increases on state highways to 70 mph. Any increases on state highways will be completed at later dates as engineering studies can be completed.