The ride-hailing service Uber is already testing self-driving cars to pick up customers in Pittsburgh with a person on standby in the driver’s seat. Lately, its driverless cars have been spotted on the streets of San Francisco.

At the same time, the list of companies with an eye on the space is growing. Apple has hundreds of employees working on autonomous car technology, and carmakers are snapping up tech talent. General Motors acquired the self-driving car start-up Cruise Automation this year, and Ford Motor is expanding aggressively in Silicon Valley with a research and development center.

For Google, the goal was to design a vehicle that is responsible for 100 percent of the driving. The company said this approach was more difficult and would take more time. However, Google said it was ultimately safer than semiautonomous vehicles, which may require a driver to take back control of the car without awareness of the surroundings.

Waymo said its ultimate goal was to equip its driverless system on cars without steering wheels or pedals because it didn’t want humans to feel as if they needed to monitor the vehicle. However, government regulations currently require a vehicle to have steering wheels and pedals.

In August 2015, Google brought in Mr. Krafcik, a former Hyundai Motor executive, to lead the project and bring it closer to commercialization. It has also lost crucial personnel on the project, sometimes to competitors.

One of the project’s founders, Anthony Levandowski, left Google in 2015 and started Otto, an autonomous trucking company that was acquired this year by Uber. He now oversees Uber’s driverless car operations. Chris Urmson, who led the project before Mr. Krafcik and served as its chief technology officer until his departure in August, is now working on his own self-driving car company, according to the technology site Recode.

“Google has struggled to find a way to come to market,” said Roger Lanctot, an associate director at research firm Strategy Analytics. “We’ve come to the point where Google needs a return.”