It’s seen to be the capital of the world’s driverless vehicle technology, but now officials in San Francisco are asking the state of California to halt or scale back the expansion plans of Cruise and Waymo.

NBC news reports repeated incidents in which cars without drivers stopped and idled in the middle of the street for no obvious reason, has delaying bus riders and disrupting the work of firefighters.

The city’s transportation officials sent letters this week to California regulators asking them to halt or scale back the expansion plans of two companies, GM-owned Cruise (pictured) and Google’s driverless subsidiary Waymo, which are competing head-to-head to be the first to offer 24-hour robotaxi service in the country’s best-known tech hub.

The TV network says the outcome will determine how quickly San Francisco and possibly other cities forge ahead with driverless technology.

NBC adds that this episode adds another chapter to the complicated history of self-driving cars, an idea that has been teased by technologists as a possibility in the future while facing a variety of setbacks in the past few years. Waymo offers fully autonomous rides in Phoenix, while Tesla lets some of its owners test “driver assistance” features that are the subject of a federal investigation.

(Picture – Cruise)