Missouri Truck Idling Law
Missouri has no single statewide idling cap, but the Missouri Air Conservation Commission enforces a heavy-duty diesel idling rule in its two largest metros: 5 minutes in any 60-minute period in the St. Louis area (City of St. Louis plus St. Louis, St. Charles, Jefferson, and Franklin counties, 10 CSR 10-5.385) and the Kansas City area (Clay, Platte, and Jackson counties, 10 CSR 10-2.385). St. Louis County is stricter at 3 minutes. Up to 30 minutes is allowed to load or unload, and running an APU complies. Separately, Mo. Rev. Stat. 304.180 grants a 550-pound weight allowance for idle-reduction technology.
When you can keep idling
- Up to 30 minutes to load or unload at a freight location
- Traffic congestion
- A safety or health emergency and emergency vehicles
- PTO and work equipment
APUs and idle-reduction gear
Running an APU instead of the main engine complies with the metro limits. Idle-reduction tech also earns up to a 550-pound weight allowance (Mo. Rev. Stat. 304.180).
City and county ordinances
- St. Louis County: stricter 3-minute idling limit, fine up to $250 (Air Pollution Control Code Sec. 612.340)
- City of St. Louis: 5 minutes per hour, 10 minutes below 32F, fine up to $100 (Ordinance 68137)
Missouri Idling Law FAQ
Is there a truck idling law in Missouri?
How long can a truck idle in Missouri?
What is the fine for idling in Missouri?
Does an APU count as idling in Missouri?
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 Traffic laws change and this can be out of date, so always confirm the current statute and obey posted signs before you rely on it.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=MO. See our Terms & Disclaimer.
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