Zipcar ads on transit. Photo: Oran Viriyincy via Flickr under Creative Commons license.

As part of the second annual Low-Car Diet, Zipcar is challenging people in 13 cities to give up their cars for one month and learn what car-free living is all about. To help wean them off of their driving habit, Zipcar is of course offering them a car sharing membership, as well as transit passes and bikes in some of the participating cities. In Chicago, 30 residents are taking part in the challenge, ditching their cars from July 15 - Aug. 15.

Visit http://www.zipcar.com/lowcardiet and click on the '08 tab to read about the experiences of participants from last year. The results showed a 71% decrease in miles driven among the participants, which would support the claim that people who use car sharing end up driving less.

There doesn't seem to be any news coverage of this in Chicago, but here's a story from Philadelphia. And in Portland, just to make other cities look bad, Mayor Sam Adams is even participating and ditching his car. Granted, Adams may also have other motivations -- but still, have you ever seen Mayor Daley ride the CTA to help promote transit?

Check out Zipcar's Chicago Low-Car Diet press release.