Montana Overweight/Oversize Permits



Oversize permits in Montana 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. Except on Red Route highways, loads not exceeding 18′ wide, 18′ high, or 120′ in length are permitted during daylight hours (one half hour before sunrise to one half hour after sunset). DW21 and 5 MPH conditions on 2-lane highways only allow daytime travel.


Width 8’6” 
Height 14′
Weight (Gross weight is 80,000 lbs)
  • Single – 20,000 lbs.
  • Tandem – 34,000 lbs.
  • Tridem – 42,000 lbs.


  • 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


Please Note: Divisible loads surpassing 80,000: You cannot exceed 80,000 lbs. of gross weight without a permit until you are legal on all axle/group weights and you are licensed for the minimum of your gross weight.


Width 18′
Height 17′
Length 150′
Weight: *
  • Single – 24,000 lbs
  • Tandem – 48,000* lbs
  • Tridem – 62,700* lbs
  •  (5 axles) * (6 axles) * (7 axles) Depends on spacings

*Variable, dependent on axle spacing

Loads which exceed these dimensions are considered as superloads.


ESCORT/Pilot Car Requirements


Width Over 16’6″ – (Needs 1 escort pilot car)
Length Over 120′ – (Needs 1 escort pilot car)


Non-Interstate – On 2 Lane or Multi-Lane

Width main body load Over 14′ or overall width is over 15′
  • Over 12’6″ – (Needs 1 escort pilot car)
  • Over 16’6 – (Needs 2 escort pilot cars)
Length over 110′ 1 Rear
Width over 12’6″ up to 14′ 1 Front
Height over 17′ (before permit application) Route Survey
Width over 10′ and not equipped with lights and signs state requires 2(Front & Rear)


Restricted Travel

Travel is not allowed on Red Route Highways after 3:00 P.M. If the dimensions exceed 10’6″ wide, 14’6″ high, or 110′ in length, travel is restricted from Fridays until Saturday sunrise, and Sundays until Monday sunrise. Furthermore, no travel is permitted after 4:00 p.m. Friday until Monday morning if the dimensions exceed 18wide, 18high, or 120in length. The Red Route Map is available online or at scales. Loads not exceeding 10′ wide, 14’6′′ high, or 110′ long are generally permitted for holiday travel.

You can also obtain any trip and fuel permits you may need with our sister site!