More than a year after Uber's self-driving trucks made their first commercial delivery -- 2,000 cases of Budweiser beer on a 120-mile hop in Colorado -- the company says it has taken its robot big rigs to the highways of Arizona.

Uber said on Tuesday that its self-driving trucks had been carrying cargo on highways in Arizona for commercial freight customers over the past few months.  [...]

At the heart of Uber's vision are transfer hubs where trucks can pick up and drop off trailers. At those locations, autonomous trucks would grab trailers for long-haul drives, while human drivers would grab ones earmarked for closer delivery -- with Uber's network meshing the supply and demand of both behind the scenes.