Humans Optional: A Vending-Machine Concept to Sell Used Cars

It works kind of like an old-style lunch automat. Instead of inserting a quarter for a piece of pie, you pay for a car online and get a code number that opens a garage door at Carvana's storage site. Carvana, which opened in January, also offers direct-to-consumer loans online. Garcia said the process can take as little as 15 minutes.

There's only one location, in Atlanta, but the company wants to expand.

Garcia says Carvana's prices are $1,500 cheaper on average than those at traditional dealerships.

The company delivers the vehicle, or the customer can pick it up. Garcia says the storage site is staffed, but it's possible for customers to do the entire transaction without having a single conversation with a human. Garcia said about 20 percent have chosen to make their purchases that way, but the company won't say how many cars it has sold.

Carvana's Web site has a "patent pending 360-degree photo process," with zoom-in capability, that allows shoppers to check out the interior and exterior of vehicles. It also has a seven-day "no questions asked" return policy.