Chris Urmson, who was instrumental in buildingGoogle’s self-driving car project, said on Friday he is leaving the team after seven and a half years.

Alphabet Inc’s Google had named Urmson chief technical officer of the project after it hired former Hyundai executive John Krafcik to be chief executive of the project.

Urmson, who joined the project when it was launched and has been a public face of Google’s autonomous vehicle efforts, testified before a U.S. Senate panel on autonomous cars in March.

Krafcik confirmed Urmson’s departure in a tweet on Friday afternoon. Urmson, in a blog post late Friday, said he was “ready for a fresh challenge.” He said he was not sure what he would do next.

“Going to take some time and get some perspective from outside of Google,” he wrote in a text message to Reuters.

Urmson told Reuters earlier this year that self-driving cars are coming. “I’ve gone from hoping this would happen to thinking it might happen to knowing it will happen,” Urmson said.

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