The move to self-driving cars is coming faster than most people think, says the head of ridesharing giant Lyft.

Within five years, autonomous vehicles will account for the majority of Lyft rides, says co-founder and chief executive John Zimmer.

Lyft, which has a partnership with General Motors on autonomous vehicles, says he sees a "transportation revolution" stemming from a shift to self-driving cars, and that by 2025 "private car ownership will all but end in major US cities."

"As a country, we've long celebrated cars as symbols of freedom and identity," Zimmer said in a Medium blog post Sunday.

"But for many people -- especially millennials -- this doesn't ring true. We see car ownership as a burden that is costing the average American $9,000 every year."

Zimmer argues that autonomous vehicles will work better as part of a fleet like Lyft's because the average car is used just four percent of the time and parked the rest of the time.

"It will be both more practical and appealing to access autonomous vehicles when they are part of Lyft's networked fleet," he writes.

Zimmer's comments come days after Lyft rival Uber launched a driverless car service in Pittsburgh, Pennsylvania, and with major automakers and technology firms racing to be part of the movement.

The shift is a huge benefit for the environment, according to Zimmer.

"Every year, more and more people are concluding that it is simpler and more affordable to live without a car," he said.

"And when networked autonomous vehicles come onto the scene, below the cost of car ownership, most city-dwellers will stop using a personal car altogether."

As a result, he commented, "cities' physical environment will change more than we've ever experienced in our lifetimes... we'll have the chance to redesign our entire urban fabric. Cities of the future must be built around people, not vehicles."