Idle Time

June 10, 2008
Don't worry about running a red light. Seems the real way to get into trouble in Minneapolis these days is letting your engine run. The city has just enacted a new law that means you'll get a hefty fine for letting your car idle for more than three minutes. The one exception is when you're stuck in traffic.

"Most of the air pollution in Minneapolis comes from vehicles and cutting down in idling is one easy thing we can all do for our environment, our health, and the health of our neighbors," said Mayor R.T. Rybak.

The logic behind the new ordinance is pretty obvious. There's the matter of air pollution, of course. Idling pumps a lot of unnecessary pollutants into the air, from smog-causing ozone to global warming CO2. And idling a car that isn't warm yet significantly increases emissions.

There's also the matter of mileage.

"In these times of high gas prices, it's a way for people to save fuel. If you're sitting in an idling car, you're getting zero miles a gallon. That's not good for your pocketbook or the environment," Rybak added.

Depending on what you're driving, you might waste as much as a half gallon an hour idling. Big semi-trucks, which generally operate with far less effective emissions controls onboard typically waste a gallon or more an hour. Minneapolis already bars commercial truckers from idling more than five minutes, and other cities are going down a similar path. In the Los Angeles area, for example, experts claim the biggest single source of pollution in the city is the line of trucks idling at Long Beach's massive port.

So how long is too long to idle? Ask a dozen experts and you're likely to get a dozen different answers. Typically, once a car is warmed up, you're better off shutting it down if you plan to sit for more than a minute, though even idling for just 30 seconds will generally waste more fuel than it takes to restart your vehicle. Exceptions? If you're sitting in traffic - as the new Minneapolis law allows - or in a relatively quick-moving line where everyone shutting off and restarting their cars would make the line move much more slowly.

Incidentally, a number of new cars will decide when to idle without your involvement. That includes full hybrids, such as the Toyota Prius, and light hybrids, like the Saturn Vue. Typically, they're designed to shut down, even at a stoplight, then restart instantaneously when you lift your foot off the brake. But even these vehicles will keep running in extremely hot or cold days to keep their climate control systems operating.

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