By JOHN MARKOFFAUG/

SAN FRANCISCO — A roboticist and crucial member of the team that created Google’s self-driving car is leaving the company, the latest in a string of departures by important technologists working on the autonomous car project.

Chris Urmson, a Carnegie Mellon University research scientist, joined Google in 2009 to help create the then-secret effort. He took over leadership of the team after Sebastian Thrun, the Stanford computer scientist and founder of Google X laboratory, left in 2013.

Johnny Luu, a spokesman for Alphabet, the parent company of X, the company’s research division that oversees the car project, confirmed Mr. Urmson was planning to leave.

“Seven years ago, the idea that a car could drive itself wasn’t much more than an idea. Chris has been a vital force for the project, helping the team move from a research phase to a point where this lifesaving technology will soon become a reality. He departs with our warmest wishes,” Mr. Luu wrote in an email message.

The departures come after Google’s decision last year to hire John Krafcik, the former president and chief executive of Hyundai America, to be chief of the car project, as part of a plan to spin the effort out as a stand-alone company under the Alphabet umbrella.

The X research group, often called Google’s “moonshot” division, is under increasing pressure to show that at some point the company can expect a financial windfall from its projects. Google’s self-driving car project has been a pioneer in autonomous vehicle technology, but a commercial version of the car is still likely to be several years away.

Mr. Urmson has been unhappy with the direction of the car project under Mr. Krafcik’s leadership and quarreled privately several months ago with Larry Page over where it was headed, according to two former Google employees. A spokesman for Google declined to comment on those discussions, but Mr. Urmson disputed they were a reason for his departure.

After the dispute, Mr. Urmson decided to take the summer off and only recently decided to leave the company. He told members of the self-driving car team about his decision on Thursday, the former employees said.

In a post published on Medium Friday afternoon, Mr. Urmson said he had not decided what he will do next. “If I can find another project that turns into an obsession and becomes something more, I will consider myself twice lucky,” he wrote. “I have every confidence that the mission is in capable hands.”

As a researcher at Carnegie Mellon, Mr. Urmson was a member of a team of engineers that placed second in the 2005 Darpa Grand Challenge contest for autonomous vehicles that was won by a rival team from Stanford, led by Mr. Thrun. In 2007, Carnegie Mellon got revenge when it placed first in the Darpa Urban Challenge, while the Stanford team finished second.

Earlier this year, a group of Google employees, led by Anthony Levandowski, former Google Car engineer, and Lior Ron, the product lead for Google Maps, left to found the self-driving truck start-up Otto, which is based in San Francisco.

More recently, two other Google car engineers, Dave Ferguson and Jiajun Zhu, who are considered experts on so-called machine vision technology, left to found an as-yet-unannounced start-up, according to the two people with knowledge of the Google car project.