Washington, DC CNN  — 

John Krafcik is exiting his role as Waymo’s CEO after nearly six years of leading the self-driving car project at Google’s parent company, Alphabet.

Krafcik, 59, said in a blog post published Friday that he is looking forward to a refresh period and discovering new parts of the world. He said he’d remain as an advisor to Waymo, and called it the “capstone” of his career in the auto industry. Prior to his role at Waymo, he worked at Hyundai, Ford, and NUMMI, a joint venture owned by GM and Toyota.

Krafcik first joined Waymo in 2015, according to a LinkedIn post from the former CEO.

Waymo will now have co-CEOs, Dmitri Dolgov and Tekedra Mawakana, who previously served as the company’s chief technology officer and chief operating officer, respectively.

Krafcik presided over Waymo’s deployment of the first fully autonomous ridehail service in Chandler, Arizona in 2018. The vehicles cover thousands of miles a week, according to Krafcik’s email. Waymo is widely considered the leading developer of fully autonomous vehicles, which do not need human supervision to drive safely.

But Waymo, like the entire self-driving industry, has struggled to hit its own deadlines. Building self-driving cars is extremely difficult and expensive. Waymo, even with the funding of Alphabet, has said it’s raised $3.25 billion in external funding. The industry is debating whether roads need to be retrofitted with sensors to speed the launch of self-driving cars.

While at Waymo, Krafcik increasingly clashed with Tesla CEO Elon Musk, whose use of the word “self-driving” has angered many autonomous vehicle experts. Waymo went so far as to stop using the term “self-driving” earlier this year. It now refers to its vehicles as “fully autonomous.”

Building a fully autonomous vehicle is a much harder challenge than the “self-driving” features that Musk offers, which are akin to an enhanced cruise control. Autonomous vehicle experts have long worried that referring to a vehicle with an enhanced cruise control as “self-driving” will cause drivers to put too much trust in the technology, leading to crashes.