San Francisco's police and fire departments have urged the CPUC to oppose the expansion – they say they've tallied 55 incidents where self-driving cars have got in the way of rescue operations in just the last six months.

"Our folks cannot be paying attention to an autonomous vehicle when we've got ladders to throw," San Francisco Fire Chief Jeanine Nicholson said in a public meeting on Monday providing commissioners testimony before Thursday's vote.

"We have demonstrated our deep willingness and longtime commitment to work in partnership with California state, SF city and first responders," said Waymo spokesperson Katherine Barna.

In one of those episodes, captured on police body camera footage obtained by Mission Local, a driverless car approached the scene of a massive fire in a residential neighborhood and inched slowly toward the firehose as frustrated first responders did all they could to stop it.

Several police officer and firefighter associations and unions in the Bay Area wrote letters to the CPUC urging the regulator to hold off on allowing the expansion of driverless car programs in San Francisco, according to Mission Local.