Montana Truck Idling Law
Montana has no statewide idling rule. The only local limits are tied to air quality around Helena, where the city and Lewis & Clark County cap idling at about 2 hours during declared poor air-quality periods. Confirm the current terms with the county health department.
Some figures on this page are flagged medium confidence. The limit and source are solid, but a specific fine or local detail should be confirmed with the state agency before you rely on it.
When you can keep idling
This state has no statewide idling limit, so there are no statutory exemptions to list. Local ordinances, where they exist, carry their own.
APUs and idle-reduction gear
No statewide rule.
City and county ordinances
- Helena and Lewis & Clark County limit idling to about 2 hours, and only during declared poor air-quality periods.
Montana Idling Law FAQ
Is there a truck idling law in Montana?
How long can a truck idle in Montana?
What is the fine for idling in Montana?
Does an APU count as idling 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 Traffic laws change and this can be out of date, so always confirm the current statute and obey posted signs before you rely on it.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://afdc.energy.gov/fuels/laws/IR?state=MT. See our Terms & Disclaimer.
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