Have you ever done it? Left your car in the driveway to warm up a few minutes before you head out to work?

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You could be breaking the law and not even be aware you are doing it. But that may not stop you from paying dearly for your ignorance. Cops really do write tickets for this infraction.

It happened in my old hometown of Detroit, Michigan earlier this year. This guy Nick Taylor got tagged for over $100 bucks just for leaving his car warming up in the driveway unattended.

"Unattended vehicle" is the reason that police are most concerned about. While we may see nothing wrong with letting our cars run a few minutes to warm up before we drive off, it's the fact that we are not INSIDE the car that creates the potential for danger - as in 'danger of a theft or accident.'

I spoke with Marion Police Deputy Chief Douglas Slagle who agreed with my understanding of the reason why it is against the law. He said "We believe the purpose of this law is to reduce the crime of opportunity of vehicle theft."

Slagle told me that the ordinance is Iowa Code Chapter 321.362. It states leaving a vehicle running and unattended, whether locked or unlocked/private or public property, is against the law.

"No person driving or in charge of a motor vehicle shall permit it to stand unattended without first stopping the engine, or when standing upon any perceptible grade without effectively setting the brake thereon and turning the front wheels to the curb or side of the highway."

And while it may not be vigorously enforced, it could still cost you a few bucks if you were written up for the infraction.

So in the name of safety, and to save yourself the aggravation be forewarned: if you warm up your car and leave it unattended - even if it's in your own driveway - you could be breaking the law, and you could get punished for it.