There are no easy answers to traffic and parking congestion in downtown Ann Arbor, but there’s one zippy answer that’s beginning to catch on.

The Downtown Development Authority has agreed to add two more vehicles to the fleet of Zipcars it sponsors, raising the total to six.

This innovative program has been a hit in Ann Arbor and a case of money well spent toward the cause of getting the community to consider alternative forms of transportation.

Zipcar is a company based in Cambridge, Mass., that offers hourly and daily rental of cars across the country. Its concept is particularly well-suited for college towns and major metro areas.

In Ann Arbor, the DDA has subsidized Zipcars by guaranteeing the company up to $1,500 in revenue for each car the DDA supports. In addition, the DDA has dedicated parking spaces for Zipcars in the public lot across from the Farmer’s Market and in a downtown parking lot at the corner of Main and Williams streets.

The subsidy to Zipcar has proven to be a modest one. As people choose to use the cars, the amount underwritten by the DDA is reduced. Over the past seven months, the authority has paid out only $3,260. The rest was covered by users of the cars.

No one is arguing that four Zipcars - or six, once two more are added to the fleet - are the solution to the crunch of parking and traffic downtown. Rather, Zipcars make sense as part of a broader strategy that also includes more incentives and opportunities for people to use mass transit, car pool, ride a bicycle or walk downtown.

But without question, Zipcars have made a splash, with their snazzy logo and the high visibility given to their premium parking spots downtown. They’re also a common sight on and around the campus of the University of Michigan, which supports a Zipcar program as well.

Modest as the cost of subsidizing Zipcars has been in Ann Arbor, supporters of the program agree that their introduction into the community has been successful and that future subsidies should not be necessary.

Outside the immediate campus area, it would have been harder for Zipcars to catch on without the DDA’s support. The concept is an easier sell in cities like Chicago where it can be cost-prohibitive to own a car in the downtown area.

Thanks to the encouragement of the DDA and getDowntown Ann Arbor, an organization that’s enthusiastically pushed Zipcar use, the concept has proven to be viable here.

Nancy Shore, director of getDowntown, told the DDA that her group will not be coming with any further requests to publicly fund Zipcars. “We have gotten it up and running,’’ she said. “It is successful.’’

That being the case, this has been seed money invested smartly. Compared to the $50 million that the city will spend to construct an underground parking structure on Fifth Avenue, encouraging the use of Zipcars has cost the public virtually nothing - while reminding us how much better it can be for the environment and for our wallets to give alternative transportation a try.

(This editorial was published in today's newspaper and reflects the opinion of the AnnArbor.com editorial board.)