Uber's fleet of self-driving trucks has begun hauling commercial loads, the company announced on Tuesday. The trucks will operate first in Arizona, a state with famously permissive laws for self-driving technology.

The trucks won't be fully driverless—they'll still have human safety drivers behind the wheel. Still, the announcement represents an important step toward the use of fully autonomous trucks in the trucking business.

Uber's driverless trucks will operate as part of Uber Freight, a freight-hauling app and network that Uber launched last year. Just as the regular Uber app lets passengers book a ride with a few clicks, Uber Freight is an app that connects shippers with truckers who can haul their loads.

And Uber is planning to organize its trucking network differently than a lot of conventional trucking companies. Instead of having a single driver hauling a load from start to finish, Uber plans to have human drivers handle relatively short legs at the beginning and end of the journey, while driverless trucks handle the long-haul route in between.

"Truck drivers possess the critical skills that self-driving trucks may never match — like backing into a tight dock, navigating a busy industrial yard, or moving axles on a trailer," Uber wrote in a November blog post. Having a human driver at each end of the trip works around the limitations of fully autonomous trucks.

And this model is potentially good for truckers, too. As Uber's network grows, the company will have to recruit a lot of truck drivers to complete these short-haul routes. With more short-haul routes, drivers will be able to spend more nights at home and fewer on the road.

How Uber’s automated trucking network will work

On Tuesday, Uber released a video to illustrate how this three-stage delivery process, called the "transfer hub model," will work. First, a human driver picks up a trailer full of cargo and drives it to a nearby rendezvous point. In the example shown in an Uber video, a driver drove about 300 miles from Los Angeles to Topock, at the western edge of Arizona.

The driver then meets up with a self-driving truck at a transfer hub in Topock and they trade loads. The self-driving truck gets the conventional driver's load to take it further east, while the conventional driver takes the load that the self-driving truck brought from the west.

The self-driving truck then handles the middle section of the trip. Uber is initially restricting autonomous truck trips to Arizona for legal reasons, so it has been hauling loads between Topock at the western edge of the state to Sanders, Arizona in the east—a distance of around 300 miles. But Uber's goal is for driverless trucks to haul loads much longer distances on trips spanning multiple states.

Finally, the load will be transferred back to another human driver, who will carry it to its final destination and deal with the complexities of handing the trailer off at its destination.

Uber hopes to orchestrate these handoffs so that each truck hands off a trailer to the other one, allowing everyone to make money on both legs of their trips.

Autonomous trucks may destroy the trucking profession in the long run. But Uber's model means that in the short run, at least, Uber is going to need to recruit a lot of truckers to participate in its freight hauling network. This will be a lot like Uber's relationship with its conventional ride-hailing drivers: Uber is dependent on human drivers in the short run, even as it works on technologies that will eventually put them out of work entirely.