Cruise, a majority-owned subsidiary of General Motors (GM), has reportedly started testing its autonomous cars in San Francisco, US, without human backup drivers.

CNBC reported that Cruise started testing its autonomous cars less than two months after receiving a permit from the California Department of Motor Vehicles.

The company is said to be one of the first to test its driverless vehicles in a dense, complex urban environment.

Cruise CEO Dan Ammann said that the company will initially begin tests with a few cars. This will be followed by a ‘very methodical and responsible’ ramp up across San Francisco.

He said: “What this represents for Cruise and, I think, the self-driving industry more generally is you’re seeing fully driverless technology out of the R&D phase and into the beginning of the journey to being a real commercial product.”

However, Ammann did not comment on the specific launch date of a commercial autonomous vehicle business for passengers or cargo.

Over the past five years, Cruise is said to have driven more than two million miles and invested billions of dollars in the operations.

Cruise spokesman Ray Wert said to CNBC in an email: “The safety operator has the ability to bring the vehicle to a stop in the event of an emergency, but does not have access to standard driver controls. Eventually, this safety operator will be fully removed.”

Wert explained that although there would be no humans in the driver seat, the company intends to keep a safety operator in the passenger seat during initial tests.

In January, Cruise unveiled an all-electric automated vehicle at an event in San Francisco.

The self-driving vehicle has been designed to operate without any manual controls such as pedals or steering wheels.