Montana OSOW permits

Permits valid for three to five days

Montana permitting system:

Contact phone number: 1-406-444-7262


Loads not exceeding 10' wide, 14'6" high, or 110' in length may travel 24/7 on all routes. Daylight hours, including Saturdays and Sundays, are allowed for loads not exceeding 18' wide, 18' high, or 120' in length except on Red Route highways. DW21 and 5 MPH conditions on 2-lane highways only allow daytime travel.


On Red Route Highways, travel is not allowed after 3:00 P.M. Fridays until Sunrise on Saturday, and from 12:00 Noon Sunday to sunrise on Monday if dimensions exceed 10' wide, 14'6" high or 110' in length; and no travel is allowed after 4:00 P.M. Friday until Monday morning if dimensions exceed 18' wide, 18' high, or 120' in length. Red Route Map is available online or at scales. Holiday travel is usually allowed for loads not exceeding 10' wide, 14'6" high or 110' long. Check with Sammons Permit Office.


Width: 8'6”

Height: 14'

Length: 53' semi-trailer, 75'maximum length if trailer exceeds 53' or if there is any rear overhang

Overhang: Overall length including overhang up to and including 75' is legal. Over 75' needs a permit.

Weight: 80,000 Gross Single – 20,000 Tandem – 34,000 Tridem – 42,000

Divisible Loads Exceeding 80,000:

You can exceed 80,000 gross without a permit as long as you are legal on all axle/group weights and you are licensed for at least the amount of your gross weight.


Width: 18'

Height: 17'

Length: 135'

Weight: * (5 axles) * (6 axles) * (7 axles) *Depends on spacings Single – 24,000 Tandem – 48,000* Tridem – 62,700* *Variable, dependent on axle spacings *

Note: DW21 Conditions: Over approximately 54,300 pounds (depending on axle spacings) on a Tridem on 2-lane highways puts you into DW21 Conditions, requiring 2 pilot cars. Over approximately 48,000 (depending on axle spacings) on a Tridem on 2-lane roads may trigger 5MPH Conditions which does not require pilot cars but restricts running to daylight only. Loads in excess of these dimensions are considered as super loads


On Interstate Highways:

Width: Over 16'6" – 1 escort

Height: Not usually required, but over 17' may depend on the route, and over 16' may have 2-lane detours.

Length: Over 120' – 1 escort

On 2-Lane Highways:

Width: Over 12'6" – 1 escort, over 16'6 – 2 escorts

Height: Over 17' – 1 escort with high pole

Length: Over 110' – 1 escort

Weight: Over 54,300 – 55,000 on a Tridem (varies with spacings) – 2 escorts (DW21 Conditions).


Vehicle/load exceeding 10’ in width require "Oversize Load" signs front and rear, and 5" flashing amber lights, revolving beacon or strobe light(s) are required at each end of the Oversize Load sign on the power unit, or a single beacon light may be used on top of the power unit as long as it is visible from all directions. If the light is blocked by the height/width of the load, the rear of the load should also have a light. "Long Load" sign must be displayed on the rear of combinations exceeding 105' on non-Interstate routes, and exceeding 120' on Interstate routes. Overlength load does not need signs if less than 110' total overall length.


Spring thaw restrictions may occur on some routes approximately February through May. Interstate routes are usually not affected. Check with Permits Office

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