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Montana Oversize Permits Information


Montana Oversize Permits are valid for 3 days.

Operating Time

Loads not exceeding 10′ wide, 14’6″ high, or 110′ in length may travel 24/7 on all routes.  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 2-lane highways only allow daytime travel.


Montana oversize permits do not allow for travel on major holidays, holiday weekends or on Red Route Highways 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, 15’6″ high or 110′ in length; and no travel is allowed on major holidays, holiday weekends or after 3:00 P.M. Friday until Monday morning if dimensions exceed 18′ wide, 17′ high, or 120′ in length.

Speed Limit

Maximum posted limits unless otherwise specified on permit.

Legal Dimensions

The vehicle must have the following characteristics:

  • 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 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.

Routine Montana Oversize Permit Limits

  • Width: 18′
  • Height: 17′
  • Length: 150′
  • Weight: Single – 24,000; Tandem – 48,000*; Tridem – 62,700*; 5 axles, 6 axles or 7 axles depends on spacing

*Variable, dependent on axle spacing;


On Interstate Highways:

  • Width: Over 16’6″ – 1 escort pilot car
  • Length: Over 120′ – 1 escort pilot car

On 2-Lane Highways:

  • Width: Over 12’6″ – 1 escort pilot car, over 16’6 – 2 escort pilot cars
  • Length: Over 110′ – 1 escort pilot car
  • Height: Over 17′ – 1 escort with high pole
  • Weight: Over 54,300 – 55,000 on a Tridem (varies with spacings) – 2 escorts (DW21 Conditions)

Security Measures

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. Over length load does not need signs if less than 110′ total overall length.

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Call: 224-998-3880

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*$25 service fee for each particular permit