Montana

Width

8'6"

Height

14'

Semi-trailer length

53'

Maximum length (includes all overhang)

75'

Legal overhang — front

3'

Legal overhang — rear

15'

Single axle

20,000 lb.

Tandem axle

34,000 lb.

Tridem axle

42,000 lb.

Max gross weight

80,000 lb.

Phone

406-444-6130

Fax

406-444-7670

Hours

8:00 AM – 5:00 PM Mountain

Website

mdt.mt.gov

Width: on the Interstate, 16'6" requires one rear escort; on non-Interstate highways, 12'6" requires one front escort and 16'6" requires two escorts (front and rear). Length: on the Interstate, over 120' long requires one rear escort/pilot car; on non-Interstate highways, over 110' requires one rear escort/pilot car. There are no published escort rules specifically for height/pole cars.

No axle may carry a load in excess of 20,000 lbs. No two consecutive axles 14–96 inches apart may carry more than 34,000 lbs combined (axles 40 inches or less apart count as a single axle). Maximum gross weight on a vehicle, axle group, or combination is determined by the formula W = 500((LN/(N−1)) + 12N + 36), where W is gross weight, L is wheelbase in feet, and N is number of axles — except that two consecutive sets of tandem axles may each carry 34,000 lbs if the overall distance between the first and last axle of the consecutive sets is 36 feet or more. Maximum load on a non-steering axle with wide-base tires is limited to 500 lbs per inch of tire width.

The time limit on all temporary trip permits is 72 hours (extensions are addressed in additional rule guidance). Vehicles used for displays or exhibitions (including circuses and carnivals) may be permitted to cover their entire schedule for a single trip through the state, with the last date in Montana shown as the permit's expiration date. Maximum permit fees must be paid. Each single vehicle or vehicle in a combination with a gross weight over 6,000 lbs may require a temporary trip permit.

All vehicles except passenger cars and pickup trucks under 14,000 lbs must stop at open Montana weigh stations. An operator is subject to penalties whenever the gross loaded weight of a truck, truck tractor, trailer, or semitrailer exceeds the gross vehicle weight shown on its registration certificate or gross vehicle weight license. The operator must immediately pay the difference between the fee paid and the applicable fee for the actual gross weight, before unloading the excess, provided it does not exceed the legal axle weight. Violations are a misdemeanor, punishable by a fine of up to $300, up to 60 days in county jail, or both.

Continuous travel — including hours of darkness, weekends, and holidays — is allowed on red route highways for loads not exceeding 10' wide, 15'6" high, and 110' long. Daylight-only travel is allowed 7 days a week, except on holidays, holiday weekends, and red routes, for loads up to 18' wide, 120' long, and 18' high. Loads exceeding 18' wide, 120' long, or 18' high are limited to daylight hours Monday through Friday. Red route highways carry additional restrictions.

A sign reading "OVERSIZE LOAD" or similar wording is required on the front and rear at any visible height, with letters at least 8 inches high, dark on a light background. There is no mention of flag requirements for the permitted hauling vehicle itself, though flags are required on escort vehicles. On the power unit, flashing amber lights at least 5 inches in diameter, 50 candlepower, flashing 60–90 times per minute, must be mounted at each end of the oversize load sign (a revolving or strobe light may be substituted); these lights must flash at all times while moving an oversize load, and full length/width lighting is required for night travel.

Tire chains, pneumatic studded tires (protrusion no more than 1/16 inch beyond the tread), or tires clearly marked "all season mud and snow" are permitted when required for safety because of snow, ice, or similar conditions, only between October 1 and May 31 of each year — except that one such tire may be used as a spare in case of tire failure.

Active — eight restrictions are in effect on named Montana state and US highway segments at listed mileposts, plus two county-maintained road segments (S-261, S-323). This is not a statewide or blanket local-road coverage.

Length

95'

Width

15'

Height

15'6"

Cost — Annual OS

$75.00

Cost — Annual OL Doubles

$125

Turnaround

1 week, mailed, truck specific

The three S's of work zone safety: Speed (follow posted limits, manage your speed carefully), Space (leave room between you and the vehicle ahead, don't pass on shoulders, give yourself an out, tap brakes to alert drivers behind), and Manage Your Stress (keep your cool, don't rush). Also pay attention (avoid cell phone/radio distractions) and expect delays — use the Traveler Information Map, leave earlier, or try an alternate route.

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