Do you want a free rental car for three days? You even get a free tank of gas. But at the end of those three days you have to give up the car and find your own way home.

That’s the idea behind Transfercar, which unites volunteer drivers wanting a (mostly) free one-way trip with rental car companies needing to relocate their fleets.

Transfercar co-founder Brian Karlson started the service in New Zealand in 2008 after observing a problem: Tourists often flew to the country’s North Island before driving to the South Island and catching a flight home. It left a glut of rental cars on the wrong island.

“It created a real imbalance,” said Dennis Round, who manages the U.S. operation.

Instead of paying to have the cars shipped by truck, Transfercar created an online platform, transfercarus.com, where drivers can search for rental cars that need relocating. The process is similar to renting a car — except the car is free. Drivers will likely be on the hook for tolls and fuel beyond one tank of gas. They typically get at least three days to move the car and have the option of keeping it longer at a discounted rate.

Launched in the U.S. in 2014, Transfercar works with Advantage and Budget rentals, plus three RV rental companies, Round said. In mid-December, more than 30 cars were available to drive from Chicago to Florida. Pickup and drop-off locations vary based on the season.