Over the past year or so, a jarring sight has become common in San Francisco: driverless cars buzzing around the city’s streets with no one at the wheel and an expensive array of electronic sensors guiding the way.

But a plan by two companies to expand driverless taxi services in San Francisco has met stiff resistance from city officials and some activists. The fight has become a Rorschach test for local tolerance of the tech industry’s new ideas: Are the driverless cars an interesting and safe transportation alternative? Or are they a nuisance and a traffic-blocking disaster waiting to happen?

With more than 800,000 residents, hilly San Francisco is the second most densely populated city in the country. Whether self-driving cars can succeed in the city will be a harbinger for their viability in other communities. And success in San Francisco could provide, for the first time, a signal that the billions invested by the tech and auto industries into autonomous driving technology could eventually pay off.

The California Public Utilities Commission, the state agency responsible for regulating self-driving cars in the city, is set to vote on Thursday on a plan to allow General Motors-owned Cruise and Waymo, which is backed by Google’s parent company, Alphabet, to charge for driverless rides throughout the city, round the clock. Right now, Cruise can offer paid rides late at night in the northwest part of the city, while Waymo offers only free rides.

The companies also operate their driverless cars without passengers in seemingly endless loops in San Francisco neighborhoods, using the cars’ real-world experiences to improve their autonomous technology.

Though the driverless cars have not been blamed for any serious injuries or crashes, local news media have reported several incidents prompting concern that the cars, when presented with an unexpected obstacle — wires in the road, fire hoses or even dense fog — simply shut down and won’t move.

Before a C.P.U.C. hearing on Monday, civic groups demonstrated outside the commission’s offices in San Francisco. Among them were taxi drivers, who feared that their jobs would be replaced by the artificial intelligence behind autonomous cars, and public transit activists. One of the activist groups, Safe Street Rebel, has even found a way to make the cars shut down by simply placing a traffic cone on their hood. Waymo has called the traffic cone pranks vandalism.

That the state — and not the city — has the final say on whether to expand the driverless car services has also frustrated community groups that have, among other things, successfully fought for expansion of bicycle-only lanes throughout the city.

“I believe deeply that the process is flawed,” said Janelle Wong, executive director of the San Francisco Bicycle Coalition. “It certainly puts the power in members of the state who do not live in these local cities or locales and experience what it is like to have these autonomous vehicles around our streets.”

The C.P.U.C.’s five members were supposed to decide on the expansion in June but delayed their vote until Thursday. The commission declined to comment on the pending vote.

At the Monday hearing, city officials argued that the cars got in the way of emergency responders and that the companies that operated them were too slow to do anything about it. The San Francisco Fire Department logged 55 incidents this year where firefighters had to deal with a self-driving car — including five reports over the past weekend.

In January, a Cruise self-driving vehicle entered an area where firefighters were working and did not stop until a firefighter started “banging on its hood and smashing the vehicle’s window,” according to city records. In May, a driverless Waymo car blocked a fire vehicle while it was backing into a station.

“It is not our job to babysit their vehicles,” said Jeanine Nicholson, chief of the San Francisco Fire Department. She said instances where firefighters had to attend to self-driving cars that wouldn’t move for 30 minutes were “unacceptable.”

City officials said they had also documented about 600 incidents involving self-driving cars, including when the cars stopped unexpectedly or made illegal turns.

The average response time during an accident was 10 minutes for Waymo and 14 minutes for Cruise, representatives of the companies said at the hearing. While technicians can offer some guidance to the A.I. system in the cars, they cannot operate the vehicles remotely.

From Jan. 1 to July 18, Cruise reported 177 rides where its vehicle was stuck on the road and had to be removed — 26 of which had a passenger inside. Waymo said it had identified 58 incidents over the first six months of 2023 where a vehicle with a passenger inside had to be retrieved.

Julia Ilina, a spokeswoman for Waymo, said in a statement that the company had no injuries to report in its first million miles of fully autonomous driving, and that every collision had been caused by “rule violations or dangerous behavior on the part of the human drivers.”

Drew Pusateri, a spokesman for Cruise, said the company reported more data to regulators “than many other vehicles on the road today.”

But Julia Friedlander, senior manager of automated driving policy at the Municipal Transportation Agency, said the companies’ data were incomplete. Waymo and Cruise are required to report the total number of collisions and incidents each quarter, but only when the incidents “impact the safety of either the passenger in the vehicle or the public.”

After Cruise’s and Waymo’s applications to expand their services in December, the city’s planning commission, along with two transportation agencies, said in a letter to the C.P.U.C. that the self-driving technology companies had to report additional data for the officials to decide whether the cars were safe enough to operate throughout the city.

In another joint letter to the C.P.U.C. in May, the agencies concluded from an analysis by the San Francisco County Transportation Authority that self-driving cars, on average, resulted in more injuries than vehicles operated by human drivers. But the C.P.U.C. said in June that the data that city officials had based their analysis on was “problematic” since it excluded incidents involving self-driving cars where the human drivers were at fault.

The local tech community has generally supported the driverless car programs. Garry Tan, chief executive of the venture capital fund Y Combinator, said in a YouTube video that the officials who opposed the expansion were “ideologically driven” and “hate technologies.”