ST. LOUIS – As the St. Louis region sees its first measurable snowfall this season, it’s a friendly reminder that colder, icier, and snowier days are just around the corner.
Naturally, it’s the time of year again when you may be tempted to start your car, leave it running, and briefly step away while it warms up to tackle frosty windshields and frigid interiors.
These few steps seem like a harmless way to prepare for wintry conditions, but be warned: This practical shortcut could steer you into legal troubles.
Is it legal to leave your car running to warm up in St. Louis? Or elsewhere in the St. Louis region? Or in the states of Missouri or Illinois?
Here’s a closer look at some laws worth knowing. Many refer to rules around warming up a car as “idling,” or as environmental experts put it, leaving an engine running while the vehicle is parked.
St. Louis City
A St. Louis city ordinance that first took effect in 2008 prohibits people from leaving a vehicle “idle” under various circumstances of time and temperature.
The ordinance indicates that leaving a vehicle “idle” for more than five minutes in any given hour or ten minutes in any given hour when temperatures are below freezing is illegal.
There are some exceptions for emergency vehicles, vehicles transporting disabled or special needs persons, and other operational or testing purposes.
Any reported violation of this ordinance could lead up to $150 in fines.
St. Louis County
St. Louis County doesn’t specifically prohibit the action of warming up a car in cold temperatures, but there are restrictions in warming up a car in accordance with the county’s air pollution code.
The county’s air pollution code indicates that leaving a vehicle “idle” for more than three minutes while parking, standing or stopped is illegal “unless the engine is being used to operate a loading, unloading or processing device.”
The only exceptions to this are for emergency vehicles.
All reported municipal code violations could lead up to $1,000 in fines.
Missouri
The state of Missouri doesn’t have a statute that explicitly prohibits the action of warming up a vehicle in cold temperatures, but there are some restrictions in the state if the vehicle you warm up is considered “heavy-duty,” like buses and semi-trucks.
The Missouri Department of Natural Resources has set forth regulations that make it illegal for “idling” of “heavy-duty diesel vehicles” for more than five minutes over any given hour in eight Missouri counties, which include five in the St. Louis area. It’s part of an effort to control air pollution.
Counties under this restriction include:
St. Louis City
St. Louis County
Franklin County
Jefferson County
St. Charles County
Clay County (KC metro)
Jackson County (KC metro)
Platte County (KC metro)
Consequences from violations may vary based on the municipality of a reported violation.
Illinois
The state of Illinois, which includes several counties in the St. Louis region, prohibits the act of warming up a car unattended in most cases.
According to the Illinois Vehicle Code, “No person driving or in charge of a motor vehicle shall permit it to stand unattended without first stopping the engine, locking the ignition, removing the key from the ignition, effectively setting the brake thereon and, when standing upon any perceptible grade, turning the front wheels to the curb or side of the highway.”
This presumably makes it illegal to leave a running vehicle idle while unattended, even if you were to briefly go inside to stay warm as your car warms up.
There are some exceptions for law enforcement officers and people authorized to drive emergency vehicles for their duties.
There is also a provision in Illinois’ Vehicle Code that states a vehicle is not considered “unattended” if it is locked and running with the engine that started using a remote starter system.
However, the Illinois Vehicle Code also makes it illegal to leave a vehicle idle for more than 10 minutes over any given hour, even if someone is attending to the vehicle as it is running.
Do rules apply to remote-starting cars?
As expressly indicated in Illinois’ Vehicle Code, it is not necessarily illegal to start a car with a remote-starter system in Illinois while unattended. Since Missouri does not have a law on such matters, the same could apply there.
However, all local and state rules on “idling” must be followed, so as most statutes that apply to drivers in the St. Louis region, anywhere from 3-10 minutes is likely the sweet spot of how long a car can warm up while running and parked.
MotorBiscuit.com explains that dozens of other U.S. states have similar laws for idling with a remote-starter vehicle in effect as Missouri and Illinois, even though there doesn’t appear to be a national law on leaving a car idle or using a remote starter to warm it up.