SAN FRANCISCO — Following years of testing with a human backup driver at the helm, General Motors’ Cruise is launching fully driverless cars onto public streets in San Francisco, the most complex urban environment robocars have taken on to date, the company announced Wednesday.

The company said Wednesday it was deploying five self-driving vehicles in San Francisco’s Sunset District, a residential and commercial corridor that encompasses many of the traits that make the city unique: densely packed streets, steep inclines and its trademark fog.

Cruise made the announcement in a conference call with its chief executive, Dan Ammann, Wednesday morning.

Cruise said it was confident enough to launch the driverless trials after five years of testing, including 2 million autonomous miles in San Francisco. The company is not the first to deploy self-driving cars without a human backup driver, and unlike competitor Waymo, which launched driverless ride-hailing in Arizona earlier this year, it will not initially be giving rides to the public.

Cruise spokesman Milin Mehta said the company began its driverless testing in November. The company, which aims to launch a fully electric, driverless ride-hailing service, said it plans to expand to other neighborhoods, as its permit encompasses the whole city. But the initial tests will not leave the driverless vehicle fully in control.

Instead, the backup driver will be effectively moved to the passenger seat in the initial phases of the permit. While those operators will not have access to traditional driver controls, they can bring the vehicle to a stop if there is an emergency, the company said.

Cruise plans to eventually remove the safety operator as well, but it did not say when.

Companies in Silicon Valley and elsewhere are racing to make driverless vehicles a reality, touting the safety implications — potentially decreasing motor vehicle deaths, which number around 40,000 annually — and the business breakthrough that would allow exponentially cheaper ride-hail trips by eliminating the need to pay a human driver.

Companies such as Cruise and competitor Zoox, acquired by Amazon this year, have set their sights on San Francisco, seeing the potential payoff of conquering a complex urban environment and the country’s second-most densely populated major city, rather than starting small and gradually increasing their capabilities. But analysts have said self-driving vehicles will have to deploy unique skill sets for each of the environments where they are dispatched.

California has issued permits for fully driverless vehicles to five companies: Waymo, Zoox, AutoX, Nuro and Cruise, according to the state Department of Motor Vehicles website.

While its competitors use gas-powered vans and SUVs in their driverless fleets, Cruise’s fleet is both self-driving and electric. The company uses Chevrolet Bolt vehicles outfitted with a driverless sensor suite.