In January, GM (GM) invested $500 million in ridesharing startup Lyft. Then in March, it spent $1 billion on Cruise Automation, a self-driving vehicle startup.

“We think rideshare is interesting, and we think autonomous vehicles is really interesting, and we think it gets really interesting if you put the two together,” Dan Ammann, GM’s president, said at Fortune’s Brainstorm Tech conference in Aspen on Monday.

The timeline for autonomous vehicles is “probably faster than what you think,” he noted. Safety is key. “It’s our fundamental belief that autonomous technology will lead to better safety on the roads.”

So what will that look like? The first known autonomous fatality, which Tesla (TSLA) announced earlier this month, sparked a news cycle’s worth of concerned headlines.

Many self-driving car proponents believe semi-autonomy, like Tesla’s Autopilot feature, is more dangerous than full autonomy (no steering wheels, no brake pedals) because humans cannot be relied upon to quickly take over driving in the event of an emergency. GM CEO Mary Barra has said her company is in the steering wheel and brakes camp.

For more on self-driving cars, read Fortune’s latest cover story, “Some Assembly Required.”

Ammann sees self-driving cars becoming a reality as “a series of developments, opening up to broader to broader as we go.” He would not name a specific timeline. (“There’s no single point answer to that question,” he said.)

“You might see something on a defined route or area or conditions, and you start to see some of those constraints fall away,” he said.

GM is also moving quickly in its alliance with Lyft, which happened via a $500 million investment in January. On Monday, the companies announced they would expand their car rental partnership to several more U.S. and international cities. “The alliance has been been significantly more successful than we ever envisioned,” he said.

Would GM buy Lyft, which is reported to be for sale? Ammann dodged the question, but noted that the company’s existing investment in the company was significant. “Half a billion is a lot of money for us,” he said.