Montana oversize permit requirements
Montana designates certain highways as Red Routes and shuts them to large loads across the weekend on a sliding scale. A load over ten feet wide, fourteen feet six high or a hundred and ten feet long may not use them after three on Friday afternoon until Saturday sunrise, nor from noon on Sunday until Monday sunrise. A load over eighteen feet wide, eighteen feet high or a hundred and twenty feet long loses the whole weekend from four on Friday. Knowing whether a route is red is the first routing question in Montana, not the last.
Away from the Red Routes the state is generous. A load within ten feet of width, fifteen feet six of height and a hundred and ten feet of length travels continuously. Up to eighteen feet wide, eighteen feet high and a hundred and twenty feet long it travels in daylight, weekends included. Routine permits reach a hundred and fifty feet of length, eighteen feet of width and seventeen feet of height — among the largest allowances anywhere.
Two named conditions attach to heavy tridems and are worth pricing in. DW21 conditions apply above roughly fifty-four thousand three hundred pounds on a tridem, depending on spacing, and require two escorts. The 5 MPH conditions apply around forty-eight thousand pounds on two-lane roads and restrict the move to daylight. Neither is a permit refusal, but both change the cost of the job. The permit runs three to five days.
Legal dimensions
At or under these figures, no oversize permit is required in Montana.
- Width
- 8′6″
- Height
- 14′0″
- Gross weight
- 80,000 lb
- Overhang
- Governed by the 75′ maximum overall length rather than published separately
- Single axle
- 20,000 lb
- Tandem
- 34,000 lb
- Tridem
- 42,000 lb
Routine permit limits
Above legal dimensions and up to these figures, Montana issues a permit as routine business. Beyond them the load becomes a superload, reviewed case by case.
- Length
- 150′
- Width
- 18′
- Height
- 17′
- Single axle
- 24,000 lb
- Tandem
- 48,000 lb, varying with axle spacing
- Tridem
- 62,700 lb, varying with axle spacing
Escort requirements
A load reaching any of these figures needs an escort in Montana — the figure is the first size that requires one, so a load measuring exactly this much already needs it.
- Width
- 16′7″
- Height
- 15′0″
When the load may move
Permit validity. Permits are valid for three to five days.
Operating time. A load within 10′ wide, 15′6″ high and 110′ long may travel continuously. A load within 18′ wide, 18′ high and 120′ long travels in daylight — half an hour before sunrise to half an hour after sunset — weekends included, but not on Red Route highways.
Restricted travel. On Red Route highways, loads over 10′ wide, 14′6″ high or 110′ long may not travel after 3 PM Friday until Saturday sunrise, nor from noon Sunday until Monday sunrise. Loads over 18′ wide, 18′ high or 120′ long may not travel after 4 PM Friday until Monday morning. Holiday travel is generally allowed for loads within 10′ wide, 14′6″ high and 110′ long.
Worth knowing
- Red Route highways carry their own weekend closures, graded by the size of the load.
- DW21 conditions apply above roughly 54,300 lb on a tridem, depending on spacing, and require two escorts.
- The 5 MPH conditions apply around 48,000 lb on a tridem on two-lane roads and restrict the move to daylight.
- Legal length is 53′ for the semitrailer and 75′ maximum with overhang.
- A load under 110′ needs no length signage; above 105′ off the Interstate or 120′ on it, a Long Load sign is required at the rear.
Montana permits, answered
What is a Montana Red Route?
A designated highway with its own weekend closures for large loads. Over 10′ wide, 14′6″ high or 110′ long, a load is shut out from 3 PM Friday to Saturday sunrise and from noon Sunday to Monday sunrise; over 18′ or 120′ it loses the whole weekend from 4 PM Friday.
Can a load travel continuously in Montana?
Within 10′ wide, 15′6″ high and 110′ long, yes. Larger loads up to 18′ wide, 18′ high and 120′ long run in daylight, weekends included, but not on Red Routes.
What are DW21 conditions in Montana?
They attach above roughly 54,300 lb on a tridem, depending on spacing, and require two escorts. They do not refuse the move, but they change what it costs.
What are the 5 MPH conditions?
They apply around 48,000 lb on a tridem on two-lane roads and confine the move to daylight.
How wide can a load be on a Montana routine permit?
18′, with 17′ of height and 150′ of length — among the largest routine allowances in the country.
Crossing more than Montana?
A permit is per state. If the route leaves Montana, these are the states it most likely enters.
Get a permit quote for Montana
Enter the load once and the estimator prices every state on the route, flags where an escort is required, and turns the quote into an order.
Price a permit for Montana →Compiled from published state DOT sources. Regulations change — confirm the current rules before dispatch. Last reviewed 2026-07-30.