By Evan Reid, Founder of Haul Handbook · Updated Sep 28, 2026
MDT Motor Carrier Services issues oversize and overweight permits through the MT eTRIPS system, by phone at (406) 444-7262, or at weigh stations. Montana's legal limits are 8 feet 6 inches wide and 14 feet high, a 53-foot semitrailer with no overall length cap, and no flat gross weight cap: gross weight follows the bridge formula up to 131,060 pounds for reducible loads. A trip oversize permit costs $10 and an annual oversize term permit $75. Loads over 18 feet wide, 17 feet high or 150 feet long are superloads that need district approval.
Montana legal limits (no permit needed at or under these)
- Width
- 8.5 ftMont. Code Ann. 61-10-102 bars a vehicle, unloaded or loaded, wider than 102 inches, with exceptions for implements of husbandry and hay hauling incidental to farming during daylight within 100 miles, and for noncommercial recreational vehicle appurtenances.
- Height
- 14 ftMont. Code Ann. 61-10-103 caps height at 14 feet, unladen or loaded, except that hay or straw moved no more than 25 miles incidental to farming may reach 15 feet 6 inches if it will meet no overhead obstacle 17 feet or lower. Signs showing structure heights are advisory only; the permittee must verify clearances.
- Gross weight
- 131,060 lbMontana has no flat 80,000-pound cap. Mont. Code Ann. 61-10-107 sets 20,000 pounds per single axle and 34,000 pounds per tandem (axles more than 40 and less than 96 inches apart) and applies the bridge formula W = 500(LN/(N-1) + 12N + 36) to every vehicle and axle group, with two consecutive tandems allowed 34,000 pounds each when the first and last axles are 36 feet or more apart. MDT's gross vehicle weight chart tops out at 131,060 pounds for reducible loads. Every axle over 11,000 pounds except the steering axle needs four tires or wide-base tires (500 pounds per inch of width). MDT's FAQ says no special permit is needed over 80,000 pounds if the vehicle is licensed for the weight and legal on axles and the bridge formula.
Axle weight limits
Gross weight is one ceiling; each axle group carries its own limit, and a load can be legal on gross weight yet overweight on an axle. Exceeding any of these needs an overweight permit.
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Permit fees
- Single trip
- $10 (Mont. Code Ann. 61-10-124(1) sets $10 for each trip permit for size over the legal limits, in addition to registration and GVW fees; triples trip permits are $20. Overweight is charged separately: a load that is legal on axles but over the bridge formula pays $10 (up to 100 miles), $30 (101 to 199 miles) or $50 (200 miles or more); a non-divisible load over legal axle weights pays $3.50 per 5,000 pounds of excess axle weight for each 25 miles of route, with weight and distance rounded up to the next increment. All trip permits are void on leaving the state.)
- Annual eligibility
- Mont. Code Ann. 61-10-124(1) sets $75 for each term permit for size. A term oversize permit covers up to 15 feet wide, 15 feet 6 inches high and 95 feet long ($75); a 100-foot doubles permit (interstate only) and an annual 120-foot non-divisible length permit are $125 each; a term triples permit is $200. Term permits may go to power units licensed in Montana, apportioned through Montana IRP, or from a reciprocal jurisdiction, and they expire December 31 with no grace period (a 95-foot doubles permit on a Montana IRP cab card runs with the cab card). Term overweight permits for non-reducible loads are sold by excess weight from 5,000 to 40,000 pounds, annually ($200 to $4,000) or by the quarter, half or three quarters plus a $10 administration fee; 15,000 pounds and up requires a vehicle weight analysis.
Single-trip permit fee schedule
A single-trip permit stacks a base fee with a weight-tiered maintenance fee, and the heaviest loads add a supervision fee.
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To price a specific load, try the oversize permit cost estimator, or compare every state on the national oversize permit table.
To see how these fees combine on real loads, walk through Montana oversize permit cost worked examples.
Escort thresholds
What the escort itself has to be
Hitting the threshold is only half of it. The escort vehicle, its equipment, its driver's certification and where it rides are all regulated, and the carrier is the one holding the permit when they are not met.
- Published thresholds
- Thresholds are MDT's permit restrictions 36a to 37f, which cite ARM 18.8.511A. Overweight loads under bridge centerline conditions add pilot requirements on non-interstate highways: a minimum of two pilot vehicles (one front, one rear) for bridge centerline moves, or one rear pilot for bridge slowdown moves, unless no bridges are crossed.
- Equipment the escort vehicle carries
- A pilot vehicle may be a passenger car or two-axle truck at least 60 inches wide, rated no more than 14,000 pounds GVWR (26,001 pounds for the permittee's service or mechanic truck), carrying an OVERSIZE LOAD sign visible front and rear with black letters at least 8 inches high on yellow, flashing amber lights of at least 5 inches and 50 candlepower at 60 to 90 flashes a minute at each end of the sign (or a revolving or strobe light), and two-way communication, staying within 1,000 feet of the load. Loads over 10 feet wide need the same sign and lights on the load and power unit.
Liability cover the permit itself requires
Distinct from your operating-authority minimums: this is the cover Montana attaches to the permit, banded by the dimension you are permitted for. Each one is sourced.
Escort rules beyond the thresholds
Knowing when you need an escort is half of it. These are the Montana rules on who may run one, what the vehicle has to carry, and how the move is conducted.
- Published thresholds
- Thresholds are MDT's permit restrictions 36a to 37f, which cite ARM 18.8.511A. Overweight loads under bridge centerline conditions add pilot requirements on non-interstate highways: a minimum of two pilot vehicles (one front, one rear) for bridge centerline moves, or one rear pilot for bridge slowdown moves, unless no bridges are crossed.
- Equipment
- A pilot vehicle may be a passenger car or two-axle truck at least 60 inches wide, rated no more than 14,000 pounds GVWR (26,001 pounds for the permittee's service or mechanic truck), carrying an OVERSIZE LOAD sign visible front and rear with black letters at least 8 inches high on yellow, flashing amber lights of at least 5 inches and 50 candlepower at 60 to 90 flashes a minute at each end of the sign (or a revolving or strobe light), and two-way communication, staying within 1,000 feet of the load. Loads over 10 feet wide need the same sign and lights on the load and power unit.
Conditions attached to every permit
The standing conditions Montana writes into the permit itself, which apply whether or not they are printed on your copy.
- Summary
- Every permit requires following posted speed limits and posted weight-restricted bridges and roads, carrying a legible printed or electronic copy, obtaining any county or city permit for local roads, checking structure clearances and 511 road conditions, and complying with ARM 18.8.101 through 18.8.1506. The permittee indemnifies the state and is liable for damage to property. Writing on a permit voids it. Permits go to power units only, and term permits transfer only to a replacement vehicle of the same company.
Travel restrictions
- Daylight only
- Non-interstate loads over 10 feet wide, 150 feet long or 15 feet 6 inches high (Interstate travel is allowed 24 hours a day, 7 days a week up to 18 feet wide (including essential services within half a mile of the interstate). Non-interstate travel is allowed around the clock up to 10 feet wide, 150 feet long or 15 feet 6 inches high; larger loads travel in daylight only. Lights must be displayed full length and width under 49 CFR 393.11 for night travel.)
- Curfews
- Permanent route restrictions include MT-35 between Polson and Bigfork (loads over 9 feet wide barred unless the origin or destination is between them), US-87 between Belt and Raynesford (12 feet 6 inches wide, with posted detours) and US-12E through Deep Creek Canyon, MP 2.4 to 33.3 (12 feet wide, 130 feet long, 15 feet high). No travel is allowed on a route placed under severe driving conditions.
- Weekend / holiday
- Holidays are New Year's Day, Memorial Day, Fourth of July, Labor Day, Thanksgiving and Christmas. A holiday on Friday or Saturday closes Friday through Sunday; on Sunday or Monday, Saturday through Monday; on Tuesday to Thursday, that day only; Thanksgiving closes Thursday through Sunday. On holidays and holiday weekends interstate loads up to 18 feet wide may still move; on non-interstate highways loads up to 10 feet wide move freely, over 10 feet up to 12 feet 6 inches in daylight only, and loads over 12 feet 6 inches wide, 150 feet long or 15 feet 6 inches high may not move. Non-interstate loads over 18 feet wide, 150 feet long or 17 feet high get no weekend travel.
- Daylight hours rule
- Interstate travel is allowed 24 hours a day, 7 days a week up to 18 feet wide (including essential services within half a mile of the interstate). Non-interstate travel is allowed around the clock up to 10 feet wide, 150 feet long or 15 feet 6 inches high; larger loads travel in daylight only. Lights must be displayed full length and width under 49 CFR 393.11 for night travel.
Superload and beyond-permit review
Loads past the standard single-trip permit thresholds get individual state review rather than an off-the-shelf permit.
Loads over 18 feet wide, 17 feet high or 150 feet long, or whose configuration or weight needs MDT Bridge Bureau review, require a superload application. Class 1 covers over 18 up to 34 feet wide, over 17 up to 24 feet high, or over 150 up to 200 feet long, with a decision due within two working days of a complete application; Class 2 covers anything beyond, decided within five working days. Class 1 and 2 approvals are good for 60 days, Class 3 for one year.
Approval comes from the appropriate MDT district administrator or designee; superload correspondence goes to mdtmcssuperload@mt.gov. Configurations of 9 axles or more go through MDT bridge review.
More Montana permit rules
- Single trip fee note
- Mont. Code Ann. 61-10-124(1) sets $10 for each trip permit for size over the legal limits, in addition to registration and GVW fees; triples trip permits are $20. Overweight is charged separately: a load that is legal on axles but over the bridge formula pays $10 (up to 100 miles), $30 (101 to 199 miles) or $50 (200 miles or more); a non-divisible load over legal axle weights pays $3.50 per 5,000 pounds of excess axle weight for each 25 miles of route, with weight and distance rounded up to the next increment. All trip permits are void on leaving the state.
- Annual permit eligibility
- Mont. Code Ann. 61-10-124(1) sets $75 for each term permit for size. A term oversize permit covers up to 15 feet wide, 15 feet 6 inches high and 95 feet long ($75); a 100-foot doubles permit (interstate only) and an annual 120-foot non-divisible length permit are $125 each; a term triples permit is $200. Term permits may go to power units licensed in Montana, apportioned through Montana IRP, or from a reciprocal jurisdiction, and they expire December 31 with no grace period (a 95-foot doubles permit on a Montana IRP cab card runs with the cab card). Term overweight permits for non-reducible loads are sold by excess weight from 5,000 to 40,000 pounds, annually ($200 to $4,000) or by the quarter, half or three quarters plus a $10 administration fee; 15,000 pounds and up requires a vehicle weight analysis.
- Annual permit details: term oversize: covers
- Up to 15 feet wide, 15 feet 6 inches high, 95 feet long (mobile or manufactured homes up to 16 feet wide and 110 feet long, also $75)
- Annual permit details: term 100 foot doubles: covers
- Combinations over 95 and up to 100 feet, interstate only and within 2 miles of an interchange
- Annual permit details: term 120 foot non divisible: covers
- Non-divisible loads up to 120 feet long; width and height need a separate permit
- Annual permit details: term triples: covers
- Triple combinations up to 105 feet (cab-over or truck) or 110 feet (conventional tractor), interstate only
- Annual permit details: term overweight: covers
- Non-reducible loads over legal axle weights, by excess weight band
- Annual permit details: term overweight: conditions
- No single axle may exceed 5,000 pounds of excess weight; at the 20,000-pound band no tandem may exceed 15,000 pounds excess. Quarter, half and three-quarter year permits carry a $10 administration fee. Term overweight permits expire at the end of a quarter.
- Annual permit details: wintertime weight: covers
- 10 percent excess weight on non-interstate highways from December 1 through March 7, up to 132,000 pounds; not valid on posted bridges or roads or with other overweight permits, and suspended early if roads thaw
- Permit insurance groups
- MDT requires a minimum of $1,000,000 combined single limit bodily injury and property damage liability per occurrence for oversize permits. Mont. Code Ann. 61-10-121 requires a carrier receiving a special permit to carry public liability and property damage insurance.
- Escort notes: published thresholds
- Thresholds are MDT's permit restrictions 36a to 37f, which cite ARM 18.8.511A. Overweight loads under bridge centerline conditions add pilot requirements on non-interstate highways: a minimum of two pilot vehicles (one front, one rear) for bridge centerline moves, or one rear pilot for bridge slowdown moves, unless no bridges are crossed.
- Escort notes: equipment
- A pilot vehicle may be a passenger car or two-axle truck at least 60 inches wide, rated no more than 14,000 pounds GVWR (26,001 pounds for the permittee's service or mechanic truck), carrying an OVERSIZE LOAD sign visible front and rear with black letters at least 8 inches high on yellow, flashing amber lights of at least 5 inches and 50 candlepower at 60 to 90 flashes a minute at each end of the sign (or a revolving or strobe light), and two-way communication, staying within 1,000 feet of the load. Loads over 10 feet wide need the same sign and lights on the load and power unit.
- Escort notes: conduct
- When pilot vehicles are required, the permittee must not delay traffic more than 15 minutes.
- Escort notes: police escort
- No fixed dimension threshold for a law enforcement escort is published on the checked MDT permit restrictions; superload moves must notify local law enforcement, fire and ambulance services before travel.
- Permit conditions: summary
- Every permit requires following posted speed limits and posted weight-restricted bridges and roads, carrying a legible printed or electronic copy, obtaining any county or city permit for local roads, checking structure clearances and 511 road conditions, and complying with ARM 18.8.101 through 18.8.1506. The permittee indemnifies the state and is liable for damage to property. Writing on a permit voids it. Permits go to power units only, and term permits transfer only to a replacement vehicle of the same company.
| Name | Detail |
|---|---|
| Wintertime Weight Permit | 10 percent excess weight on non-interstate highways December 1 through March 7; $50 for 30 days or $150 for the season. |
| Custom Combine Permit | Calendar-year permit in lieu of GVW fees and oversize permits: nonresidents pay $40 per unit plus $30 fuel permit per unit and $35 per combine; residents pay 35 percent GVW fees and $20 per unit. |
| Implement Dealer Term Permit | Oversize term permit for resident dealers in implements of husbandry, transferable among the dealer's equipment, not restricted from weekend or holiday travel, expiring December 31. |
| Canadian weight permits (Eureka-BC, Alberta-Shelby, Plentywood-SK) | Border corridor permits on US-93, I-15 and MT-16 allowing Canadian train weights (A-train 118,000; 7-axle B-train 124,600; B-train 137,500 pounds) only with oversize and overweight permits. |
The Montana permit office
- Apply or log in (MT eTRIPS (online self-issue permitting, live since December 2025))
- etrips.mtmdt.us
- Agency
- Montana Department of Transportation, Motor Carrier Services Division (Licensing and Permitting Section)
- Address
- Motor Carrier Services, PO Box 4639, Helena, MT 59604-4639 (office at 2701 Prospect Avenue, Helena)
Legal size and weight limits
Montana's legal width, height and trailer length come from statute, and a tractor-semitrailer or double combination with legal-length trailers has no overall length limit. Hay and straw moved a short distance incidental to farming get extra height.
Weight works differently from most states. There is no flat gross cap: each single and tandem axle has its limit, every vehicle and axle group must satisfy the bridge formula, and MDT's gross weight chart runs well past the usual interstate figure for reducible loads. Every axle but the steer needs dual or wide-base tires above a set load.
How the fees work
Let's break it down. Size is a flat charge: one fee for an oversize trip permit and a higher one for triples, set in statute. Weight is priced two ways. A load that is legal on its axles but over the bridge formula pays a single fee chosen by the length of the route. A non-divisible load over legal axle weights pays for each increment of excess axle weight over each stretch of the route, with both weight and distance rounded up.
Term permits trade the per-trip charge for one annual fee: oversize, long doubles, non-divisible length and triples each have their own. Term overweight permits are sold by band of excess weight, for the year or by the quarter, and the heavier bands need a vehicle weight analysis.
When you need pilot vehicles
Montana sets pilot vehicle counts by width, height and length, and the interstate and non-interstate rules differ: wide loads off the interstate take front pilots first, while on the interstate they take rear pilots. Tall loads take a front pilot with a height pole. Overweight moves under bridge centerline conditions add pilots on non-interstate highways.
Pilot vehicles carry an OVERSIZE LOAD sign, amber flashing lights and two-way radios, stay close to the load, and may not hold traffic past a set delay.
Night, holiday, and route limits
The interstate allows round-the-clock travel for most permitted widths. Off the interstate, narrower loads move day and night, and larger ones move in daylight only. Holidays close for wide loads, and the closure stretches across the weekend when the holiday falls near one. A few highways carry their own permanent limits, including the road between Polson and Bigfork and the canyon stretch of US-12.
Superloads and bridge review
Loads past the superload width, height or length lines, or whose weight or axle layout needs Bridge Bureau review, go through a superload application approved by the MDT district administrator. Larger classes take longer to decide, and approvals hold for a set period. MDT names no single gross weight that makes a load a superload; heavy moves are screened by vehicle weight analysis and bridge review instead. Superload moves must notify local law enforcement, fire and ambulance services before travel.
How to read this page
A value reading "Not confirmed" means we could not verify the figure on an official agency page at review time, so it stays open rather than guessed. Superload moves above the standard permit thresholds get individual review by the state; contact the permit office named on this page. For the rest of the Montana permit stack, see Montana trucking permits.