Department of Transportation
MDT
Montana • United States of America
The Montana Department of Transportation (MDT) manages over 10,300 miles of state highways spanning the fourth largest state by area in the nation. Key freight corridors include I-15, I-90, and US-2 serving as critical arteries for the agriculture, energy, and mining industries. Montana's vast distances and severe winter weather make MDT's road condition reporting and commercial vehicle restriction system essential for truckers. The department operates the 511 Montana system, administers oversize and overweight permits, and manages critical mountain passes including MacDonald Pass and Homestake Pass. MDT coordinates with Canadian border crossings at Sweetgrass and other points of entry.
| Official Website | https://www.mdt.mt.gov/ |
|---|---|
| Founded | 1913 |
| Headquarters | Billings |
Available Data
Social Media
- @mdtroadreport — MDT Road Report
Montana Trucking Regulations
Size & weight limits, OS/OW permits, and seasonal restrictions for commercial vehicles
Weight Limits
| Category | Limit |
|---|---|
| Max Gross Vehicle Weight | 80000 lbs |
| Single Axle | 20000 lbs |
| Tandem Axle | 34000 lbs |
Dimensional Limits
| Category | Limit |
|---|---|
| Max Height | 14 ft |
| Max Width | 8.5 ft |
| Max Length (Single Unit) | 40 ft |
| Max Length (Combination) | 75 ft |
OS/OW Permits
Seasonal Restrictions Oct, Nov, Dec, Jan, Feb, Mar, Apr, May
Mountain passes have chain requirements from approximately October through May. Spring weight restrictions apply on some state and county roads during the thaw period. Many rural roads in eastern Montana are gravel and subject to spring weight limits.
Weigh Station Bypass
33¢/gal
Member
Special Exemptions
Notable Rules
Montana allows longer combination vehicles (up to 75 ft) on designated state routes. The state is vast with long distances between services; fuel and rest stop planning is critical. I-90 and I-15 are primary freight corridors. The Marias Pass and Rogers Pass are challenging mountain crossings. Grain harvest season generates significant agricultural haul activity on rural roads.