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Permits by state
What MDT Motor Carrier Services requires before an oversize or overweight load moves in Montana: legal limits, trip and term permits, pilot vehicles, and holiday rules. Sourced from MDT and the Administrative Rules of Montana.
Last verified: against official state sources.
The numbers
| Dimension | Legal limit |
|---|---|
| Width | 8 ft 6 in |
| Height | 14 ft 0 in |
| Length | Single unit 55 ft; 53 ft trailer; loads overhanging the trailer limited to 75 ft overall |
| Gross weight | Set by axle limits and the bridge formula (61-10-107 MCA); verify with the state |
A single-trip over-dimensional permit is needed for loads over 8 ft 6 in wide, 75 ft long or 14 ft high (single unit over 55 ft).
Source: MDT 2026 Size, Weight & Safety Trucker's Handbook (PDF). Checked Oct 15, 2026.
Permits
MDT moved to the eTRIPS permitting system (hosted by ProMiles) in December 2025; superloads are processed there too. Published fees from MDT's handbook:
| Permit | Fee |
|---|---|
| Single trip oversize | $10.00 |
| Term over-dimensional, 95 ft long / 15 ft wide / 15 ft 6 in high | $75.00 |
| Term, 120 ft non-divisible length | $125.00 |
| Overweight trip permits | By excess axle weight per 25 miles, from $3.50 (see handbook) |
Superloads: loads over 18 ft wide, 150 ft long, 17 ft high, or needing Bridge Bureau approval require a super-load permit. MDT may require local, utility and route-survey approvals, a travel plan, and limited travel days or hours.
Permits require at least $1,000,000 combined single-limit liability insurance.
Sources: MDT Trucker's Handbook (PDF); ARM 18.8.509. Checked Oct 15, 2026.
Pilot cars
| Situation | Requirement |
|---|---|
| Non-interstate, over 12 ft 6 in to 16 ft 6 in wide | 1 front pilot |
| Non-interstate, over 16 ft 6 in to 18 ft wide | 1 front and 1 rear |
| Non-interstate, over 18 ft to 24 ft wide | 2 front and 1 rear |
| Non-interstate, over 24 ft wide | 2 front and 2 rear |
| Interstate, over 16 ft 6 in to 18 ft wide | 1 rear pilot |
| Interstate, over 18 ft wide | 2 rear pilots side by side |
| Over 17 ft to 24 ft high | 1 front pilot with height pole |
| Over 24 ft high | Front pilot with height pole plus 1 rear |
Moves needing pilots must not delay traffic more than 15 minutes.
Sources: ARM 18.8.511A; MDT Permit Restrictions (PDF). Checked Oct 15, 2026.
When you can roll
| Highway | Rule |
|---|---|
| Interstate | 24/7 including holidays up to 18 ft wide; over 18 ft wide cannot travel on holidays or holiday weekends |
| Non-interstate | 24/7 up to 10 ft wide, 150 ft long, 15 ft 6 in high; over 10 ft to 12 ft 6 in wide daylight only; over 12 ft 6 in wide, 150 ft long or 15 ft 6 in high: no holiday or holiday-weekend travel |
| Weekends | Loads over 18 ft wide, 150 ft long or 17 ft high: no weekend travel |
Holiday dates: see MDT's Holiday Restrictions sheet.
Sources: ARM 18.8.509; MDT Permitting Reference & FAQ (PDF). Checked Oct 15, 2026.
Permit office
Phone (406) 444-7262. Apply in MT eTRIPS. mdt.mt.gov: Permits for Commercial Motor Carriers
Rather not deal with it? Run your load through our permit checker, then call (310) 989-6530.
Quick answers
The legal width in Montana is 8 ft 6 in without a permit.
The legal height in Montana is 14 ft 0 in without a permit.
On non-interstate highways, loads over 12 ft 6 in to 16 ft 6 in wide need one front pilot vehicle.
Loads over 18 ft wide, 150 ft long, 17 ft high, or needing Bridge Bureau approval require a super-load permit.
A single trip oversize permit is $10.00.
Answers summarize the sourced sections above. Last verified Oct 15, 2026.
Keep reading
For lanes, industries and how we plan Montana moves, see Heavy Haul Trucking in Montana. For cross-state answers on pilot cars, legal width and height, superloads and holiday rules, see the Heavy Haul FAQ.
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