RelayRides, a peer-to-peer car-sharing company, announced today an expansion of its airport service to provide members with free parking at San Francisco International Airport (SFO) when they rent out their cars.

The free parking service — which provides travelers with transportation to and from the airport as well as a free car wash — builds on RelayRides' existing airport marketplace that allows owners and renters to coordinate rentals themselves at or near over 180 airports nationwide.

With plans already in place to expand the free parking program to other U.S. airports, airport rentals may be the source of the majority of RelayRides' total revenue within one year, according to the company.

"Since we started RelayRides, our renters and owners have inspired most innovations in our marketplace, including a more convenient and affordable solution for airport rentals," said RelayRides CEO Andre Haddad. "As our marketplace has matured, we've seen our owners and renters look to facilitate longer weekly, and even monthly rentals. We're very excited to be able to provide our community more ways to share their cars, and save time and resources."

According to the company, the new airport parking and rental initiative will have the same rules as all RelayRides rentals today, where renters are required to replace the gas they use and purchase insurance based on their needs.

Since its launch in 2012, RelayRides peer-to-peer marketplace has expanded to serve members in more than 1,600 cities nationwide.