Amazon.com Inc.'s (AMZN  ) self-driving car unit Zoox on Wednesday said it will soon begin testing in Austin, Texas, and Miami.

What Happened: The two cities will mark the fourth and fifth public testing locations for Zoox. The company started in San Francisco in 2018 and has since expanded to Las Vegas and Seattle.

The company will initially deploy its Toyota Highlander (TM  ) test fleet retrofitted with its Automated Driving System (ADS) in small areas near business and entertainment districts of the two cities. These vehicles will also have safety drivers.

Zoox won't be deploying its purpose-built robotaxis or offering public rides to the two cities yet. The company continues to target Las Vegas and San Francisco as its first commercial markets.

"We're laying the foundations for our autonomous ride-hailing service in new cities across the US. Austin and Miami offer key learning opportunities that will support the continued growth and refinement of our testing and service," Senior Director of Policy and Regulatory Affairs Ron Thaniel said in a statement.

Competitors: Alphabet Inc's (GOOGL  ) (GOOG  ) autonomous driving unit, Waymo, currently offers fully autonomous rides to its employees in Austin, the headquarters of EV giant Tesla Inc. (TSLA  ), which is currently laser-focused on enabling vehicle autonomy and plans to have a "robotaxi unveil" in August.

GM's (GM  ) autonomous driving unit Cruise had suspended operations in the U.S. late last year following the involvement of one of its robotaxis in an accident in San Francisco. The company resumed manual driving in the city of Phoenix to gather road information in April and in Dallas, Texas earlier this week.

Why It Matters: Amazon acquired Zoox for $1.3 billion in 2020. Last month, U.S. auto safety regulator National Highway Traffic Safety Administration (NHTSA) commenced an investigation into 500 Zoox vehicles owing to concerns about its sudden braking leading to collisions.

The regulator then said that it was aware of two incidents involving Zoox vehicles in which they braked abruptly and without warning, leading to rear-end collisions.

The preliminary evaluation of about 500 Zoox vehicles will scrutinize the performance of the Zoox ADS, especially concerning the reported collisions. It will also assess the system's behavior in crosswalks around vulnerable road users and in other similar rear-end collision scenarios, the regulator said.