Idaho Has Ended Its Split Speed Limit
Date Published
Idaho used to hold heavy vehicles below the posted limit that passenger traffic ran. It no longer does, and the change is recent enough that most reference tables have not caught up.
What the statute now says
Idaho Code 49-654 subsection (3), as amended by 2026 chapter 108, provides that for vehicles with five or more axles operating at a gross weight of more than 26,000 lb, the maximum lawful speed limits on interstate highways, in nonurban areas, in urban areas, on state highways or in other locations shall be the same as for vehicles with fewer than five axles operating at 26,000 lb or less.
The same as. A five-axle combination now runs whatever the segment is posted at.
The limits it now shares
Subsection (2)(a) sets the underlying figures. Seventy-five miles per hour on interstate highways, which the department may increase to eighty on a given interstate after an engineering and traffic study if the transportation board concurs. Sixty-five on state highways, raisable to seventy on the same basis. Thirty-five in a residential, business or urban district unless otherwise posted, and fifty-five in other locations, up to a maximum of seventy.
How to confirm it yourself
The amendment is visible in the statute's own history line, which records the chain of amendments ending at 2026, chapter 108. That history line is the fastest way to check whether any speed statute has moved, and it is the check most secondary sources do not perform.
Why so many tables are still wrong
Speed limits are the most frequently amended corner of state vehicle law. Legislatures have been steadily equalising splits for years, and a comparison table is accurate only as of the day it was compiled. Idaho is simply the most recent example.
The practical consequence is narrow but real: a driver relying on a table published before the amendment will run slower than required on Idaho interstates, which is lawful but is not what the table claims to be telling them.
What is left
Seven states still hold trucks to a lower limit than cars on at least some roads: California, Oregon, Washington, Montana, Michigan, Indiana and Arkansas. Idaho is no longer among them.