Self-driving tech company Waymo has confirmed it is expanding its testing program in Phoenix.

The California-based firm, owned by Google parent Alphabet Inc, has been active in the Arizona city for several years, using autonomous Chrysler Pacifica minivans with human back-ups to carry passengers in a 50 square-mile area of the East Valley.

But a blog post published on its website last week explained significant developments in two specific areas.

“In the coming weeks, we will begin rider-only trips —with no human driver behind the wheel— with our employees in Downtown Phoenix.”

And it went on to reveal: “Additionally, the Waymo Driver [the company’s self-driving system] is beginning to drive at Phoenix Sky Harbor International Airport, with an autonomous specialist present.”

The news that Waymo will provide driverless rides in the downtown area comes merely weeks after it started operating in the area, albeit with safety drivers. At the same time, Waymo confirmed it was offering driverless trips to employees in San Francisco, and now that service will be mirrored in Phoenix. It is likely to be extended to members of the company’s Trusted Tester program in the months ahead. 

Waymo also provided more detail about what it has planned for its activity at Sky Harbor International, an important hub that is one of the 10 busiest airports in the world.

The company’s fleet of Jaguar I-Paces will drive autonomously at Sky Harbor at all hours of the day and night, with an autonomous specialist present at first. Operations will be focused on the area around the 44th Street PHX Sky Train Station, which is near the pick-up and drop-off location for other ride-hail services. 

Again, the company will begin with Waymo employees hailing rides between downtown Phoenix and Sky Harbor before the service is eventually opened up to members of the public via the Trusted Tester program.

Waymo is especially keen to observe how its cars fare with Sky Harbor’s busy roads and crowded parking lots, as airports have long been considered a challenge for autonomous cars. Picking up and dropping off, in particular, poses specific problems as the areas where this is permitted are often restricted, and driverless cars have to identify the best spots and times to do so.

The findings of the trial will be closely monitored, and as the Waymo blog acknowledged, “what we learn at Sky Harbor Airport will benefit us in other locations and help accelerate our progress.”