State Oversize Permits & Escorts Information


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Montana DOT Phone Number: (406) 444-7262

DOT Website

PERMITS: Montana oversize permits are valid for three to five days

OPERATING TIME: Continuous travel is allowed for loads not exceeding 10′ wide, 15′-6″ high, or 110′ in length.  Daylight hours (½ hour before sunrise to ½ hour after sunset), including Saturdays and Sundays, is allowed for loads not exceeding 18′ wide, 18′ high, or 120′ in length except on Red Route highways. DW21 and 5 MPH conditions on two-lane highways only allowed daytime travel.

RESTRICTED TRAVEL: On Red Route Highways, travel is not allowed after 3:00 pm 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 pm 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.

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  • 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 permit.

Width: 8′-6”

Height: 14′

Weight: 80,000 Gross

  • Single – 20,000
  • Tandem – 34,000
  • Tridem – 42,000

Note: 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.

Length: 150′

Width: 18′

Height: 17′

Weight: * (5 axles) * (6 axles) * (7 axles) *Depends on spacings

  • Single – 24,000
  • Tandem – 48,000*
  • Tridem – 62,700*

*Variable, dependent on axle spacings

You must be registered for at least the amount of weight you are permitting for Montana.

* Note: DW21 Conditions: Over approximately 54,300 pounds (depending on axle spacings) on a Tridem on two-lane highways triggers DW21 Conditions, requiring two pilot cars. Over approximately 48,000 (depending on axle spacings) on a Tridem on two-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 superloads


On Interstate Highways:

Length: Over 120′ – one escort,

Width: Over 16′-6″ – one escort

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

On two-Lane Highways:

Length: Over 110′ – one escort


  • Over 12′-6″ – one escort
  • Over 14′ – two escorts

Height: Over 17′ – one escort with high pole

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

SIGNS, FLAGS & LIGHTS: 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.

SEASONAL LOAD (WEIGHT) RESTRICTIONS: Spring thaw restrictions may occur on some routes approximately February through May. Interstate routes are usually not affected.

Important Notice:
The following is provided for informational purposes only. We do not procure or arrange permits on behalf of carriers or discuss permit and escort requirements for particular shipments. The following links provide general guidelines for oversize permits and escorts for heavy haul shipping by state/province. State regulations are subject to change; If you find inaccurate information, please let us know, and we will update the page accordingly.