Concerns about the behavior of Waymo's autonomous taxis, following the December blackout in which the cars clogged intersections and created potential hazards, are being raised at a Monday hearing at SF City Hall.

Waymo executives have been called to speak at Monday's meeting of the SF Board of Supervisors' Land Use and Transportation Committee, and they will face questions from supervisors about how the robocars behaved during the December 20 outage. The outage was triggered, in part, by a fire at a PG&E substation at Eighth and Mission streets, and for some residents the blackout lasted more than 24 hours.

During the initial hours of the blackout, which impacted about one-third of the city, Waymo's vehicles appeared confused about how to navigate intersections where traffic signals were out, and that hesitancy led to backups and potentially dangerous situations.

"The stalled Waymos were actually disrupting emergency vehicles from accessing the PG&E substation that caused the fire in the first place," says Supervisor Bilal Mahmood, speaking to KQED.

Mahmood says that the purpose of Monday's hearing is to "get answers from Waymo about what were the causes of the technical failure for some of their vehicles that day, and simultaneously, what are they doing to prevent this from happening again."

Waymo explained in a December 23 blog post that the primary issue was that the AV software prompted the vehicles, en masse, to seek human "confirmation" from a control team about how to navigate each signal-less intersection.

"While we successfully traversed more than 7,000 dark signals on Saturday, the outage created a concentrated spike in these requests," the company said. "This created a backlog that, in some cases, led to response delays contributing to congestion on already-overwhelmed streets."

They further said that these human confirmation prompts were part of the cars' "early deployment," and they said they were "now refining them to match our current scale."

Waymo has since said that its software has been updated to do avoid further incidents like this, but Mayor Daniel Lurie and others publicly questioned whether the cars might not become a greater hazard in the event of an earthquake or widespread fire, when roads need to be cleared for emergency vehicles.

Waymo was brought before the Public Utilities Commission and an administrative law judge in early January to face questions about the outage incident, and Waymo attorney Jack Stoddard declined to say how many of the cars stalled due to these confirmation delays — calling this a "trade secret," as the Chronicle previously reported. That hearing drew protests from the Teamsters union, which has been a frequent critic of Waymo regulations, and ride-hail drivers as well.

These groups, along with the California Gig Workers' Union, have been calling for the DMV to remove all autonomous vehicles from the streets.

"Why is it these vehicles are allowed on the road when they don’t follow DMV regulations?" asks labor activist Steve Zeltzer, speaking to KTVU. "If you’re a human driver you get cited, your license can be taken away. What is the accountability for these Waymo robot taxis? There is no accountability."

This is a developing story.

Previously: Waymos Were Looking for Human Remote 'Confirmations' at Intersections During Blackout, Company Says

Top image: walden_yan via Twitter