After the September launch of its first fleet of self-driving cars in Pittsburgh, ride-hailing service Uber has recently confirmed that the tests of the company’s self-driving cars have also been commenced in the city of San Francisco.

Uber has apparently told Inverse that it is testing its self-driving cars in San Francisco; but has not divulged the expected timeline for the availability of those cars to consumers hailing Uber rides in the city.

Uber is hopeful that the ongoing testing of its self-driving cars on San Francisco roads will prove useful for the company in bringing about improvements in the technology before giving the city’s residents the option of hailing self-driving Uber cars.

About the self-driving cars being tested in San Francisco, Uber told Inverse that the cars are “for internal use only.” The company also said that the cars “have a safety driver upfront” and are not a part of the company’s ride-hailing service in the city.

Highlighting the importance of testing self-driving cars in different environments, Uber said that such tests are “critical to the future success of self-driving technology, which will help improve road safety and cut congestion over the long term.”