With another blast of arctic air enveloping the region and promising to stay around for the next few days, vehicle owners might be tempted to start their cars and wait indoors for them to warm up.

John Elder of the Minneapolis Police Department advises against that, unless you have a remote starter. During the cold snap earlier this month, he said, the department saw a spike in car thefts as people left vehicles running with the keys inside and the doors unlocked.

"Auto theft of idling vehicles is a serious concern," Elder said. "During a real cold snap, we see a spike of thefts tied to people trying to warm up their vehicles. It's cold. I get that, but we should be sitting in our cars."

Overall, car theft in Minneapolis has been down between Nov. 1 and Jan. 16, the period for which Elder looked at crime statistics. But activity picked up earlier this month when temperatures sunk to minus 20 and colder. In December, there was a mini rash of auto thefts. In one two-week period, Minneapolis police responded to 62 calls for stolen vehicles. In one precinct, 11 of those were idling cars with no driver inside.

A Minneapolis city ordinance says that if a vehicle is on a city street, parkway, alley or the equivalent and the keys are in the ignition, the driver must be inside the car or be "in physical control" of it. That means the driver could be standing outside the vehicle, but must be close enough to respond should something unexpected happen. He gave the example of a car that on its own shifted out of gear and began to roll.

In St. Paul, a city ordinance says that anybody leaving a motor vehicle unattended on any street, alley or parking lot "shall lock the ignition, remove the key and take it with him or her." It also directs any police officer who discovers keys in the ignition of an unattended vehicle, running or otherwise, "to remove the keys and deliver them to the desk officer at the city's central police station."

The rules are different for cars parked on private property, such as in residential driveways. In those cases, the driver does not have to be in the car or even near it, but Elder doesn't recommend that.

"People can easily work at not being a victim," he said, adding that they need to wear warm clothing and stay with their vehicles.

Whether on public or private property, Minneapolis has rules as to how long a car may run without moving. With few exceptions, the city's Anti-Idling Vehicle Ordinance restricts gas- or diesel-powered vehicles to idling no more than three minutes in a one-hour time period. When temperatures drop below zero, as they are forecast to do this week, that time limit is extended to 15 minutes.

The law went on the books in 2008 with the goal of reducing harmful emissions, said Patrick Hanlon, the city's environmental initiatives manager. He said the city gets about 20 calls a year from residents. Last week, he said, he got one from residents who live near Target Center; they complained about idling trucks lined up outside the arena.

In most cases, violators are given a warning. Elder said officers who spot a driverless vehicle idling for an "extended time" can issue the vehicle's owner a warning or even a ticket.

St. Paul does not have an idling ordinance. Neither does Bloomington. But before you warm up your car, check with your city to be sure you are following the rules.

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