Near the Mojave desert, on the Arizona-California border, freight trucks drive in and out of the Topok weigh station. If you speed past the dusty roadside stop you likely wouldn't notice anything remarkable, but something out of the ordinary is happening there.

The Topok port of entry is one of the places where Uber has been testing transfers to and from its self-driving big rigs.

The company said Tuesday that its testing stage in Arizona is now over and that it's beginning to use its autonomous truck fleet to move freight across the state for multiple customers.

It'll work this way: A regular semi truck with a human driver will load up its trailer at a city port or other loading area and drive to a transfer station, like Topok. There, the freight gets transferred to one of Uber's self-driving trucks, which will then drive it long-distance across the state to another transfer station. A regular big rig with a human driver will take over again and drive the trailer the final short haul into an urban area.

"We've been really hard at work the past several months improving the technology," Alden Woodrow, Uber's self-driving truck product lead, said in a press call. "We're building something that solves problems in the industry … and also makes truck drivers' lives easier and better."

Uber is mostly known for its ride-hailing service, which matches passengers with drivers through a smartphone app. But over the last three years, it has ventured into driverless vehicles. Uber is now testing cars and trucks in Pennsylvania, California and Arizona.

While its autonomous vehicle program has gotten Uber into trouble more than once -- like when it rolled out self-driving cars to passengers in San Francisco without a license and when it was sued by Google for allegedly stealing self-driving car technology -- the company is now looking to work with regulators and do things by the books.

Much of that initiative comes from Uber's new CEO, Dara Khosrowshahi, who took over the company in August after the ouster of former CEO and co-founder Travis Kalanick. Khosrowshahi has emphasized that he will be an empathetic leader who competes fairly.

For its commercial launch of self-driving trucks, Woodrow said Uber has been working closely with regulators and law enforcement. Initially the semis will be just in Arizona, but Uber is hoping to expand to other states.

Uber's idea is to have several transfer hubs around the county, which would work similarly to the Topok weigh station -- connecting automated long-haul routes with drivers specializing in local hauls. The reason human drivers are doing the urban hauls is that self-driving trucks are still learning to navigate cities' crowded and complex streets.

"Because we are still in research and development mode, the capabilities are changing all the time," Woodrow said. "In general, the trucks are pretty capable of driving on the highway, and that's what we're designing them for."

Uber always has a safety operator who's a licensed truck driver at the wheel of the self-driving trucks, Woodrow said. These drivers are also trained in controlling autonomous vehicles. Certain situations, such as construction zones or accidents, can present challenges for the trucks, and a human driver may need to take over.

"We want to make sure our trucks can operate safely in those types of circumstances," Woodrow said, and "be able to navigate the dynamics of the interstate."

Along with building self-driving trucks, Uber has created an app platform called Uber Freight. Similar to the ride-hailing app, it lets trucking companies and their drivers connect with shippers. This app is already being used in the trucking industry around the US, and Uber's autonomous semis will be available on this platform.

"The trucking industry is very large and very sophisticated," Woodrow said. "Generally our goal is to partner with companies in the industry."

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