Los Angeles, California - Waymo has announced that Los Angeles, a city notorious for its traffic jams, is the next city to get its robot taxi service after Phoenix and San Francisco.

In the coming months, self-driving vehicles will arrive in the central districts of this sprawling city of 13 million people, the Google sister company announced.

The taxis won't be quite driverless just yet, and for now a human will also be behind the wheel as a safety measure. In the state of Arizona, however, Waymo cars in Phoenix are already on the road completely autonomously, while in San Francisco, the robot taxi service is under construction.

Proponents of self-driving cars for hire, such as Los Angeles Mayor Eric Garcetti, believe they will help reduce mobility costs in the long term by reducing the need to own a car, while also easing congestion and pollution by reducing the numbers of cars.

"If we want to change the car culture in Los Angeles, we need to give Angelenos real alternatives to owning their own vehicle – including a world-class public transportation network, a range of active transportation options, and the convenience of mobility as a service across our city," Garcetti said.

Waymo, which emerged from Google's self-driving car program, is one of a handful of companies that want to establish themselves with autonomous taxis. Competitors include the General Motors subsidiary Cruise and Zoox, which was bought by Amazon.