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Montana Oversize / Overweight Regulations

What is considered as "Oversized Load" in Montana?

Dimensions: Width: 8' 6" Height: 14'" Semi Trailer Length: 53' Maximum Length: 75' (includes all overhang) Legal Overhang: Front: 3', Rear: 15'

What is considered as "Overweight Load" in Montana?

Weights: Single Axle: 20,000 lb. Tandem axle: 34,000 b. Tridem: 42,000 Max Gross Weight: 80,000 lb.

Montana Oversize / Overweight Permits

Montana Permit Department Contact Information


Fax: 406-444-7670

8:00 AM - 5:00 PM Mountain

Montana Pilot Cars / Escorts


Interstate: At 16'6 you need 1 rear escort.

Non Interstate: At 12'6 you need 1 Front escort. At 16'6 you need 2 escorts, 1 front and 1 rear pilot car.


Interstate: Over 120' long you will need 1 rear escort/pilot car.

Non Interstate: Over 110' you will need 1 rear escort/pilot car.


No Published rules for pole cars.

Montana Axle Regulations

Maximum Legal Axle Loads

An axle may not carry a load in excess of 20,000 lb.
No two consecutive axles more than 14 in. or less than 96 in. apart may carry a load in excess of 34,000 lb.
Axles 40 in. or less apart are considered to be a single axle.
The maximum gross weight allowed on a vehicle, group of axles, or combination of vehicles must be determined by the formula:

                       W = 500((LN/(N - 1)) + 12N + 36),


                             W = gross weight,
                              L = wheelbase in feet, and
                             N = number of axles
                          (except two consecutive sets of tandem axles may carry a gross load of 34,000 pounds each if the
                           overall distance between the first and last axle of the consecutive sets of tandem axles is 36 feet or more.)

The maximum load on load on an axle, other than a steering axle, equipped with wide-base tires is limited to 500 pounds for each inch of tire width. 

Maximum Axle Weights

Single                                   20,000 lb.

Tandem                               34,000 lb.

Tridem                                Per State Weight Table

Maximum Permit Weights

Single                                   28,000 lb.

Tandem                               46,000 lb.

Tridem                                60,000

Quadrum                            80,000 lb.

Montana Trip and Fuel (IRP / IFTA) Permits

Time Limit: The time limit on all temporary trip permits shall be 72 hours. For extension of temporary trip permits, see additional information in this rule.

Vehicles used by displays or exhibitions (including circuses and carnivals) may be permitted to cover the period of their schedule for a single trip through the state.

The last date the vehicle is to be in Montana is shown as the expiration date on all temporary trip permits issued to displays, exhibitions, carnivals, and circuses.

Maximum permit fees must be paid.

Each single vehicle or each vehicle in a combination with a gross weight of over 6,000 pounds may require a temporary trip permit.

Montana Overweight / Oversize Fines

All vehicles except passenger cars and pickup trucks under 14,000 lbs are required to stop at open Montana Weigh Stations.

(1) The operator is subject to penalties whenever the gross loaded weight of any trucks, truck tractor, trailer, or semitrailer operated upon any highway in this state exceeds the gross vehicle weight shown on:

(a) the owner's certificate of registration

(b) the gross vehicle weight license issued under this part.

(2) In addition, the operator shall immediately pay to the nearest county treasurer or to the  department the difference between the fee already paid and that applicable to the gross weight of the vehicle before unloading the excess, provided that it does not exceed the legal axle weight.

Any owner or operator of a motor truck, truck tractor, trailer, semitrailer, bus, or automobile who violates any provision of this part is guilty of a misdemeanor and shall be punished by a fine of not more than $300 or by a sentence of not more than 60 days in the county jail or both.

Fines for weight in pounds in excess of the  maximum legal weight will be subject to the following fines:

Weight                                                               Fine

1-2,000 lb.                                                         $30.00

2,001 – 4,000 lb.                                              $75.00

4,001 – 6,000 lb.                                              $125.00

6,001 – 8,000 lb.                                              $175.00

8,001 – 10,000 lb.                                            $250.00

10,001 – 12,000 lb.                                          $275.00

12,001 – 14,000 lb.                                          $300.00

14,001 – 16,000 lb.                                          $400.00

16,001 – 18,000 lb.                                          $500.00

18,001 – 20,000 lb.                                          $600.00

20,001 – 25,000 lb.                                          $1000.00

25,001 lb. and Over                                          $2000.00

Running Hours and Holiday Restrictions

Oversize Banners

A sign with the words "OVERSIZE LOAD" or similar wording mounted at any visible height on the front and rear of the load. Letters shall not be less than 8 inches in height. The letters shall be dark in color on a light colored background.

Flag Requirements:

Flags are required on escort vehicles. There is no mention of flag requirements for the permitted hauling vehicle.

Warning Lights:

On the power unit, flashing amber lights, a minimum of five inches in diameter, 50 candlepower, 60 to 90 flashes per minute, shall be mounted at each end of the oversize load sign.   (A revolving light or strobe light may be substituted for flashing lights

Lights shall be flashing at all times when moving an oversize vehicle or load.

Lights must be displayed full length and width for night travel.

Flags, Lights and Banners

Continuous Travel Allowed:

For dimensions that do not exceed 10 feet in width; 15 feet 6 inches in height; 110 feet in length, travel is permitted during hours of darkness, weekends, and holidays on red route highways.

Travel allowed daylight hours

If dimensions do not exceed 18 feet wide, 120 feet long, 18 feet high, travel is permitted seven days a week, except on holidays, holiday weekends and red routes.

For loads that exceed 18 feet wide or 120 feet long or 18 feet high, travel is allowed daylight hours Monday through Friday.

Red route highways have additional restrictions.

Montana Tire Regulations

It is permissible to use tire chains of reasonable proportions or pneumatic tires, studded tires, that may not protrude more than one-sixteenth of an inch beyond the tire tread or that are clearly marked by the manufacturer on the sidewall "all season mud and snow", upon a vehicle when required for safety because of snow, ice, or other conditions tending to cause a vehicle to skid.

The use of pneumatic tires embedded as provided in this section is permitted only between October 1 and May 31 of each year, except that one of those tires may be used for a spare in case of tire failure.

Montana Frost Laws

Load Restrictions and Road conditions may be obtained from the Helena Maintenance Office of The Montana Department of Transportation by phoning (406)444-6372.

 Or, via the Montana Travel Conditions - Load and Speed Restrictions website:

Montana Annual Permits

Annual Permit:

Maximum Dimensions: 

  • Length: 95′
  • Width: 15′ 
  • Height: 15′ 6”


  • Annual OS - $75.00
  • Annual OL Doubles - $125

Time, it takes to receive: 1 week

Mailing method: mail 

Truck specific

Montana Road Conditions

The Three "S's"  of Work Zone Safety

1. SPEED - Follow posted speed limits, and manage your speed carefully.

2. SPACE - Leave room between you and the vehicle in front of you.
                    Do not pass on shoulders.
                    Give yourself an Out.
                    Tap breaks to alert drivers behind you that you are slowing
3. MANAGE YOUR STRESS -Keep Your Cool. Calm down. Don't rush.

4. PAY ATTENTION - Avoid cell phone or radio distractions, as well as those of other stopped cars or construction
5. EXPECT DELAYS - Use the Traveler Information Map to learn about construction
                                       Leave a bit earlier
                                       Try an alternate route.

Montana Manufactured Houses and Mobile homes

Annual/term permits are valid up to 16'0” wide, 110'0” long and 15'6” high.

See also: Lights (running lights) and axle weights sections.

Oversize / Overweight Regulations By State