Montana Truck Speed Limit
Split state. Trucks are capped at 70 mph on rural interstates where cars run 80, a 10 mph gap (MCA 61-8-312; 61-8-303). Off the interstate you are held to 65 mph day and night on any other public highway. Cars run 70 by day and 65 at night there, and 75 by day and 70 at night on four-lane national highway stretches of 10 miles or more (MCA 61-8-303(1)(b), HB 312 of 2025), so the daytime gap opens to 10 on those. Montana scrapped its old 'reasonable and prudent' non-limit years ago, so the number is enforced now.
How fast a truck can run in Montana
Split state. Trucks are capped at 70 mph on rural interstates where cars run 80, a 10 mph gap (MCA 61-8-312; 61-8-303). Off the interstate you are held to 65 mph day and night on any other public highway. Cars run 70 by day and 65 at night there, and 75 by day and 70 at night on four-lane national highway stretches of 10 miles or more (MCA 61-8-303(1)(b), HB 312 of 2025), so the daytime gap opens to 10 on those. Montana scrapped its old 'reasonable and prudent' non-limit years ago, so the number is enforced now.
Truck-specific rules and quirks
- Night limit: 65 mph for trucks on two-lane highways at night
- Montana raised the truck interstate limit from 65 to 70 in 2015; cars run 80. The old 'reasonable and prudent' daytime non-limit is long gone.
What a speeding ticket costs
Speeding is a graduated fine. Work-zone penalties double.
Montana Truck Speed Limit FAQ
What is the truck speed limit in Montana?
Do trucks have a lower speed limit than cars in Montana?
What is the speeding penalty for a truck in Montana?
Reference information for planning, not legal advice. Traffic laws change and this can be out of date, so always confirm the current statute and obey posted signs before you rely on it. Last reviewed July 2026. Source: https://www.iihs.org/topics/speed/speed-limit-laws. See our Terms & Disclaimer.
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