General Motors is set to dramatically expand its fleet of autonomous Chevrolet Bolts in San Francisco, Detroit and Scottsdale, Arizona, according to documents filed with the Federal Communications Commission (FCC), IEEE Spectrum reports.

New short- and medium-range radars will be deployed in 300 self-driving Chevrolet Bolts, perhaps beginning as soon as next month. That will give GM and its autonomous technology subsidiary Cruise Automation the largest fleet of self-driving cars in the world.

Right now the largest such fleet belongs to Waymo, which says it has around 80 vehicles on public roads in the United States, with nearly 100 more arriving shortly.

GM says it currently has more than 50 Bolts with autonomous technology in the three cities. The remaining 27 manufacturers testing in California together account for just 89 vehicles, although Ford, Uber and start-up nuTonomy at least are also testing elsewhere.