Whether you're warming up your vehicle in the driveway on a cold morning or leaving your vehicle running outside of a store for a quick trip inside, it is illegal in Maryland to leave an unattended motor vehicle with its engine running.
An unattended running vehicle is an open invitation to car thieves. Don't give them the opportunity.
Sec. 21-1101 of Maryland's Vehicle Laws states, "a person driving or otherwise in charge of a motor vehicle may not leave it unattended until the engine is stopped, the ignition locked, the key removed, and the brake effectively set."
The fines for violation are $70 and one point assessed on a driver's license or $110 and three points if contributing to an accident.