New Jersey residents who like to let their cars idle for an extended period of time before hitting the road might want to brush up on state law. If a police officer has the inclination, he or she could write a ticket for up to $1000. The crime? Excessively warming up a motor vehicle's engine.

According to News 12, the law stipulates that automobile owners are permitted to let their cars warm up for 15 minutes, but only if the vehicle has been parked for more than three hours and the temperature is less than 25 degrees Fahrenheit. Cars that were running less than three hours prior only get three minutes. A first offense can result in a $250 fine; a second, $500; and a third, $1000. The law even applies if the car is parked in a private driveway.

And yes, the state is serious. But why be so harsh on idlers? It's actually for a good reason. According to a state fact sheet [PDF] on the practice, excessive idling of a gas or diesel engine releases contaminants into the air, with fine particle pollution responsible for health issues. Since the offense is difficult for law enforcement to actually witness first-hand, the state encourages citizens to report violations. The state makes exceptions for refrigerated trucks, emergency vehicles, and vehicles stopped in traffic.

The state has also debunked a commonly-held myth that cars need to be “warmed up” in order to avoid engine damage. Electronically-controlled vehicles need just 30 seconds or so, with drivers cautioned to avoid rapid acceleration or high speeds for the first four miles during cold weather. The practice of warming up was more applicable to older model cars that used carburetors that needed to get air and fuel into the engine. Today’s cars use sensors to monitor temperature and make the correct adjustments. Idling is now just a waste of fuel, though the practice persists—people like warm cars.

While the attempt to freshen the air may be admirable, New Jersey residents are probably correct in thinking the law may be rarely enforced. From 2011 to 2016, only a few hundred summonses for violating the idling law have been written annually. In 2015, 276 were issued, with 148 of them dismissed.

[h/t News 12]