Montana Oversize and Overweight Permits

When Montana requires a permit and how to get one

MDT's Motor Carrier Services Division issues permits from Helena through eTRIPS, which went live in December 2025; trip, term and GVW permits self-issue there when no special approval or route analysis is needed (ARM 18.8.508), and an approved permit must be paid within 24 hours. Single-trip permits run for the dates printed on them and are void once the load leaves Montana, and term permits run January 1 to December 31 with no grace period (ARM 18.8.504). Special permits go only to non-reducible loads unless a rule says otherwise, and divisible loads are permitted only up to 9 ft wide, with wider allowances for hay (ARM 18.8.513).

Without an override, single trips reach 18 ft wide, 17 ft high and 150 ft long, and anything larger is a superload. Term permits stop at 15 ft wide and 95 ft long; MDT's FAQ lists term height as 14 ft 6 in, ARM 18.8.512 allows term or trip permits to 15 ft 6 in (the figure the FAQ gives for non-divisible loads), and the statute says 14 ft or a limit the department sets. Every permit carries at least $1 million combined single limit insurance with the insurer named on it (ARM 18.8.801), and only MCS staff may amend one; altering any word or figure voids it.

Fees

Permit fees come on top of registration and GVW fees, and an IRS Form 2290 is required at 55,000 lb and over. A vehicle weight analysis is required for term permits over 10,000 lb of excess axle weight (MDT lists it from the 15,000 lb tier). eTRIPS takes Visa, MasterCard, American Express, Discover or ACH, with an online payment fee and card processing fee passed to the carrier, and no separate superload or engineering fee appears in statute, rule or MDT's pages.

Travel times, curfews and holidays

Montana's hours turn on Interstate versus non-Interstate (ARM 18.8.509(8)): Interstate loads up to 18 ft wide may move around the clock every day of the week, holidays too, and trips to services within one-half mile of the Interstate, while non-Interstate loads move around the clock only within 10 ft wide, 150 ft long and 15 ft 6 in high.

• Larger non-Interstate loads: daylight only, from a half hour before sunrise until a half hour after sunset on the U.S. Naval Observatory tables; night travel needs the 'Request Nighttime Travel' box on the eTRIPS routing page, with the highway, mileposts, times and a reason. Loads running at night display lights full length and width under 49 CFR 393.11.
• Weekends: there is no general weekend ban, but on non-Interstate highways loads over 18 ft wide, 150 ft long or 17 ft high do not travel on weekends (Restriction 1e, July 27, 2026; MDT's January FAQ prints it without the non-Interstate limit). Implement dealer permits may not restrict weekends, and a harvest machinery permit may not be refused only because travel falls on a weekend.
• No city curfews: MDT's rules, permit restrictions and current order (checked Oct 17, 2026) show no rush-hour curfew for any Montana city.
• Corridor limits: MT-35 between Polson and Bigfork is closed to loads over 9 ft wide unless the trip starts or ends between them, and US-12 MP 2.4–33.3 through Deep Creek Canyon is limited to 12 ft wide, 130 ft long and 15 ft high. On US-87 between Belt and Raynesford, Restriction 47 sets 12 ft 6 in while MDT's July 22, 2026 order lists US-87 MP 0–10.42 at 12 ft, so we plan to the narrower figure until MDT confirms they are the same segment.
• Severe conditions: no travel on a route MDT has placed under severe driving conditions (ARM 18.8.509(6)), and a superload permit may bar travel in inclement weather. Loads may not delay school buses and should keep delays to passenger buses short (Restriction 3).
• Speed on overweight permits: 55 mph or the posted limit, one overweight vehicle per bridge, and no stopping or shifting gears on a bridge (ARM 18.8.602(2)).

What catches carriers in Montana

Crossing into a neighboring state

• West into Idaho over Lookout or Lolo Pass: ITD stops red-route travel from 2 PM Friday until Monday, makes every oversize vehicle stop at each port of entry beginning with Huetter on I-90, and sends US-12 loads over 16 ft wide or 150,000 lb in the Lochsa corridor to Forest Service review; see our Idaho ITD permit and escort rules.
• South into Wyoming on I-90 toward Sheridan: Montana's 24-hour Interstate allowance to 18 ft wide stops at the line, so the load's hours are re-planned there, and on back roads toward the Wyoming and South Dakota corner, S-323 from Ekalaka to Alzada carries a standing 8-ton single axle limit. Wyoming's own rules are on our Wyoming oversize permit page.
• East into North Dakota on I-94: MDT's staffed Wibaux weigh station (406-795-9972) sits near the line, and Restriction 33 makes permitted loads over 10 ft wide, 15 ft 6 in high or 120 ft long cross its scale when it is open. North Dakota's permit rules are on our North Dakota oversize permits page.