How to read a Montana oversize permit
Montana oversize permits come from MDT Motor Carrier Services through MT eTRIPS, which went live December 8, 2025, and many carriers issue their own permits online. Your permit lists numbered restrictions (like 1a, 1b, 37a) that set when you can run and how many pilot cars you need, and MDT's Montana Permit Restrictions sheet spells out what each number means.
Issued by the Montana Department of Transportation, Motor Carrier Services Division through MT eTRIPS (Electronic Transportation Routing and Intra/Interstate Permitting System). Written from MDT's published rules; we haven't read a real Montana permit yet.
How to read the route
MDT has not published a sample eTRIPS permit, so we can't show how the route is laid out. eTRIPS builds the route. Its Pre-Trip Planning tool (MDT says it used to be called bid route) checks height structures, construction and incidents and gives the miles, but MDT says that route is 'a suggested route only – not valid for Travel.' Only the route on your issued permit counts. If the permit says 'page 1 of ?', it is not valid without the other pages and any attachments.
Road names on Montana permits
| On the permit | Means |
|---|---|
| I-15 | Interstate 15 |
| US-87 | U.S. Highway 87 |
| MT-35 | Montana Highway 35 |
| S-427 | Montana secondary highway 427 (MDT marks secondary highways with an S- prefix) |
| MP 2.4 | Milepost 2.4 |
Where the route starts and ends
MDT's published documents don't show how eTRIPS prints the start and end of a route. Some standing restrictions name places in plain words, for example 'between Shelby MT and the Montana-Alberta border at Sweet Grass on I-15.'
Conditions to watch for
Interstates: 24/7
On Interstates you can run any hour, any day, up to 18 feet wide. Lights must show your full length and width. Source
“Interstate highways – travel is allowed 24 hours per day, 7 days per week, up to 18 feet wide”
Other highways: daylight for big loads
Off the Interstate you can run 24/7 up to 10 feet wide, 150 feet long and 15 feet 6 inches high. Anything bigger moves in daylight only. Source
“Loads exceeding 10 feet wide, 150 feet long, and/or 15 feet 6 inches high may travel during daylight hours only.”
Holidays
Holidays are New Year's Day, Memorial Day, Fourth of July, Labor Day, Thanksgiving and Christmas, plus the weekend days around them. On those days, loads over 18 feet wide can't run on Interstates. On other highways, loads over 12 feet 6 inches wide, 150 feet long or 15 feet 6 inches high can't run. Source
“Loads exceeding 18 feet wide cannot travel on Holiday or Holiday Weekends.”
Weekends
Off the Interstate, loads over 18 feet wide, 150 feet long or 17 feet high can't travel on weekends. Source
“Non-interstate highways: Loads exceeding 18 feet wide, 150 feet long, or 17 feet high, are not allowed weekend travel.”
Pilot cars
Off the Interstate you need one front pilot over 12 feet 6 inches wide, and front and rear pilots over 16 feet 6 inches. On the Interstate you need one rear pilot over 16 feet 6 inches wide. Over 17 feet high, you need a front pilot with a height pole. Source
“loads exceeding 12 feet 6 inches wide to 16 feet 6 inches wide must have one front pilot vehicle”
Signs and lights
Over 10 feet wide, put an 'oversize load' sign on the front and rear: black letters on yellow, at least 8 inches tall. Mount flashing amber lights on the power unit at each end of the sign, and keep them flashing while you move. Source
“Letters shall not be less than 8 inches in height.”
Easy to miss
- A Pre-Trip Planning route in eTRIPS is not a permit. MDT calls it a suggested route that is not valid for travel.
- Don't write on your permit. MDT says writing on it voids it. Only the permittee signature is allowed, and only MCS staff can change a permit.
- Some roads have standing limits. One example is MT-35 between Polson and Bigfork: no loads over 9 feet wide unless the load starts or ends between those towns.
Questions
Can I drive an oversize load at night in Montana?
On Interstates, yes: MDT allows travel 24 hours a day up to 18 feet wide, with lights showing full length and width. On other highways you can run at night up to 10 feet wide, 150 feet long and 15 feet 6 inches high. Bigger loads move in daylight only.
When do I need a pilot car in Montana?
Off the Interstate, one front pilot over 12 feet 6 inches wide, front and rear over 16 feet 6 inches, and more over 18 and 24 feet. On the Interstate, one rear pilot over 16 feet 6 inches wide and two rear pilots side by side over 18 feet. Loads over 17 feet high need a front pilot with a height pole.
Is my eTRIPS Pre-Trip route the same as my permit route?
No. MDT says a Pre-Trip Planning route is a suggested route only and is not valid for travel. Drive the route on your issued permit.
Sources
Your permit is the legal document; follow everything it says. Rules change; check MDT's site before you move.Last checked October 2026.