Uber Technologies Inc. expects it will be a long time before one of its self-driving cars, is ready for wide-scale deployment, a senior scientist said Monday.

Raquel Urtasun, who heads the Uber Advanced Technologies Group (ATG) in Toronto, spoke about the challenges for self-driving development at a Reuters Newsmaker event in New York.

“Self-driving cars are going to be in our lives. The question of when is not clear yet,” Urtasun said. “To have it at scale is going to take a long time.”

“What is clear is that in a 10-year time frame there will be a mix of both [self-driving and human-controlled cars],” she said.

This is a different stance compared to Uber's tactics some years ago, when the company was sharinmg hype and bold promises on its autonomous vehicle plan.

The first setback for Uber came last year, when one of its autonomous SUVs killed a pedestrian in Tempe, Arizona.

In any case, the extreme technical challenges of building cars that can predict human behavior and respond appropriately proved greater than it had been anticipated.

Uber reported losses before taxes, depreciation and other expenses of $1.8 billion last year. The company has been spending millions of dollars on its self-driving unit, and prepares to kick off its initial public offering this year.

The goal for Uber is to eventually remove the drivers and add automation, to its vehicles in order to pocket the full fare that passengers pay.

After the fatal Arizona crash, Uber removed its autonomous cars from the road, laid off hundreds of test drivers and shuttered operations in Arizona, its testing hub. Uber resumed very limited testing on public roads in Pittsburgh in December.

Uber has recently taken a more collaborative approach, inviting General Motor Co.’s self-driving car unit Cruise and Alphabet Inc.’s Waymo to put their cars on Uber’s ride-hailing network.

A group of investors led by SoftBank Group and Toyota Motor are in talks to invest $1 billion or more into Uber’s self-driving vehicle unit, Reuters reported last month.

Toyota has also invested $500 million to jointly develop self-driving cars with Uber.