For the third time in a row, Austin Rothbard found himself on vacation, in a scenic place that was perfect for motorcycling, without a motorcycle or any way to rent one.

That led to an epiphany: The country is full of motorcycles that aren’t being ridden, and might be full of riders like him who wanted to rent them.

The result is Twisted Road, Rothbard’s peer-to-peer bike rental service, which the entrepreneur is calling “the Airbnb of motorcycles.”

Some riding enthusiasts are applauding. But insurance experts are raising questions about liability, as they have about Airbnb and other sharing startups.

Launched late last year in Texas, the service is now nationwide, with a network of around 400 motorcycles and more than 5,000 registered users in 40 U.S. states, including Minnesota. Bikes typically rent for $75 to $150 a day.

“We’re connecting the owner with six bikes in the garage with the rider who’s traveling and really wants to ride,” Rothbard said. “We’re offering people an experience they can’t have any other way.”

Owners are protected by a clause that requires all renters to be bike owners who carry their own motorcycle insurance. For hosting the exchange, Twisted Road takes 30 percent of the transaction cost, plus extra fees for other services.

It’s similar to a motorcycle sharing service called Riders Share, whose founding officer believes Rothbard and Twisted Road are courting disaster. Los Angeles-based Riders Share, founded a year earlier than Twisted Road, offers peer-to-peer bike rentals nationwide on the same short-term basis. But Riders Share’s pitch differs from Rothbard’s in one essential point: Riders Share carries its own insurance. Renters, who must be legal licensed riders, are required to buy the Riders Share insurance before they rent a motorcycle.

Insurance experts also sounded a cautionary note.

“If a person borrows a motorcycle they also need to check with their insurer,” said Janet Ruiz, of the Insurance Information Institute. “As with automobiles, policies vary and sometimes do offer coverage when you lend your motorcycle. It can be a costly mistake if you don’t have the right coverage.”