The state of New Jersey is reminding residents that it's against the law to keep a vehicle idle for more than three minutes.

Dino Flammia, Townsquare Media NJ

The law has actually been on the books for decades, but there hasn't been a great amount of enforcement. That's because, according to Lawrence Hajna with the New Jersey Department of Environmental Protection, the state is less focused on citations and more focused on education.

"We want people to be aware of the fact that idling a vehicle does create pollution," Hajna said, noting smog is a particularly pressing issue during the summer months.

And, according to the state, idling an engine for just 10 seconds uses more fuel than turning the vehicle off and then on again.

Hajna said mobile sources - cars, trucks and buses - account for about 50 percent of ozone population. The department's hotline - 1-877-WARN-DEP - receives hundreds of idling complaints per year, but in most cases it doesn't make sense to send an inspector because by the time someone gets to the scene, the vehicle is long gone.

Hajna estimated that less than a dozen idling fines, which start at $250, are doled out in a given year.

"We're not trying to be heavy-handed about this," he said. "This is really all about protecting public health and thinking about your neighbor and thinking about the person down the street or the person who's even in the vehicle next to you."

Hajna cited a "really aggressive campaign" to educate the public on the dangers of idling, including routine compliance advisories and the website Residents, at times, are also reminded of the rule with signage at their local shops and restaurants.

The three-minute idling law has some exceptions, including vehicles stopped in traffic, emergency vehicles in an emergency situation, and buses that are releasing or picking up passengers. The law does apply to school buses, however.