GM employees in San Francisco have begun testing a fleet of self-driving taxis on public roads.

In an interview with TechCrunch, Kyle Vogt, founder and CEO of GM's Cruise automated driving division, revealed the company has begun beta trials of its new Cruise Anywhere service.

Using a smartphone app, select Cruise employees are able to request a lift in a similar fashion to Uber and other ride-hailing services. Unlike those publicly available apps, cars summoned by Cruise Anywhere are all self-driving Chevrolet Bolt hatchbacks.

These electric hatches are fitted with extra hardware and the necessary software to drive autonomously. Currently the service is limited to roads mapped by Cruise, and availability is sometimes constrained by the fleet size, which is set to grow to 100 by the end of the year, and the needs of the R&D team.

Due to local regulations, Cruise's fleet of autonomous Bolts require a certified employee seated in the driver's seat to take over when required. According to Cruise, human intervention has only been needed a few times, with the bulk of the driving done by the cars themselves.

The company says around 10 percent of its workforce is currently enrolled to use the Cruise Anywhere app, with some people using it as their main form of transportation.

There's no word yet on when Cruise will begin testing the Cruise Anywhere system in other cities or open the service to the public.

Cruise Automation was acquired by GM in March, 2016, for an estimated US$1 billion ($1.3 billion).