Google Inc. is looking for auto industry partners to bring its vision of a self-driving car to market within the next five years, the head of the software giant’s autonomous-vehicle project said Friday.

“We don’t particularly want to become a car maker,” Chris Urmson, the project’s director, said in an interview. “We are talking [with] and looking for partners.”

Mr. Urmson said his team, in the meantime, is working with automotive suppliers to build a fleet of more-advanced, “beta one” prototype Google cars, moving three generations beyond the stripped-down models shown last spring. Google plans to start on-road testing of these cars early in 2015.

The biggest challenges for Google’s efforts involve software, not hardware, Mr. Urmson said. Google is confident, for instance, that it has laser radar technology, or LIDAR, that can provide accurate images of a car’s surroundings at a reasonable cost, he said.

The self-driving car project is at the center of Google X, the search giant’s secretive skunk works lab that is working on contact lenses that measure blood-glucose levels, balloon-powered Internet service, giant TV screens, the Web-connected eyewear Google Glass, and more.