Maryland’s Idling Law (Transportation Article §22-402)
A motor vehicle engine may not be allowed to operate more than 5 consecutive minutes when the vehicle is
not in motion, except as follows:
o When a vehicle is forced to remain motionless because of traffic conditions or mechanical difficulties
over which the operator has no control;
o When it is necessary to operate heating and cooling or auxiliary equipment installed on the vehicle;
o To bring the vehicle to the manufacturer’s recommended operating temperature; or
o When it is necessary to accomplish the intended use of the vehicle.
Maryland gov IDLE REDUCTION TECHNOLOGY pdf
They are probably more concerned with Summer when the Air Quality gets crappy.
Probably means almost no one gets a ticket for idling.