Uber Technologies is getting out of the self-driving truck business. The company said it will halt development of its self-driving tractor-trailer system to focus all of its autonomous-vehicle research and development efforts on cars.

It's a significant shift, one that suggests the company is feeling growing pressure to deliver self-driving taxis before it falls too far behind fast-moving rivals.

Here's what we know.

Uber said it will shut down its Otto self-driving truck effort to focus on self-driving taxis. Image source: Anheuser-Busch InBev N.V.

A $680 million self-driving truck effort, now shut down

Trucks weren't originally part of Uber's business plan. But the company made a big splash when it acquired self-driving truck start-up Otto in 2016 for a reported $680 million, adding Otto's talent to its Pittsburgh-based self-driving research team.

The publicity continued later in 2016 when Otto partnered with Anheuser-Busch InBev's Budweiser brand, in what was billed as the world's first commercial shipment by self-driving truck. A self-driving Otto semi successfully took a trailer loaded with Budweiser beer from an Anheuser-Busch facility in Fort Collins, Colorado, to Colorado Springs -- a distance of about 120 miles.

Otto and Budweiser partnered on the first-ever self-driving beer delivery in 2016. Image source: Anheuser-Busch InBev N.V.

At the time, it looked like self-driving trucks were only a few years away. Uber seemed well-positioned to emerge as a leader in what could be a very lucrative space. Earlier this year, Uber said that it was planning to begin integrating self-driving trucks into its Uber Freight offering, using the automated trucks on longer trips to reduce costs.

But Uber's priorities -- and its leadership -- have gone through some big changes since that much-talked-about beer delivery.

Uber has a bigger priority than trucks right now

Many things have changed at Uber since it purchased Otto, starting with its CEO: Founder Travis Kalanick departed last year after a series of scandals. His replacement, Dara Khosrowshahi, has revamped Uber's culture and refocused Uber on its core ride-hailing business.

CEO Dara Khosrowshahi has brought Uber back to basics, refocusing on delivering profitable ride-hailing. Image source: Uber Technologies.

Now, though, Uber and Khosrowshahi are coming under considerable pressure. It's widely believed that Uber won't be profitable until its human ride-hailing drivers are replaced by robots, in the form of self-driving vehicles. The investment case for Uber assumes that it will use its existing business to establish itself as a major player in the coming world of automated urban mobility.