Having a car can be a joy, and a pain. There's nothing quite like driving on an open stretch of highway, the windows down, on a warm summer day with the stereo blasting to give you a sense of freedom. Conversely, there's nothing like getting a $2000 repair bill to make you question the sanity of the world around you. What if you could have the freedom of the car without the hassles?

That is the model that Zipcar is working under, and apparently it is doing something right because the company just announced that it has raised $21 million, in its series g round of funding. The round was led by Meritech Capital Partners, which gave $20 million of the funding. The rest came from Pinnacle Ventures.

The service, which mostly serves urban areas and college campuses, boasts more than 500,000 members sharing roughly 8,000 vehicles in the United States, Canada and the United Kingdom, after it acquired UK car sharing company Streetcar for $50 million earlier this year. The company will  use the funds to finance the growth of its fleet of vehicles and continue its geographic expansion. Users of the service have about 30 makes and models of vehicles to choose from.

The Cambridge, Massachusetts-based Zipcar, which currently allows for either hourly or daily rentals of vehicles, has been in existence since 2000. In addition to buying the above-named Streetcar, Zipcar also merged with  Flexcar in October 2007. Competitors include Connect by Hertz. Another potential competitor, RelayRides, which works on a person-to-person sharing model, is currently in its pilot testing.

Zipcar has yet to respond to an inquiry about which locations it will expand into.

(Image from Zipcar)