Waymo is being questioned about its failures during a widespread power outage in San Francisco.

The December incident saw many of the autonomous robo taxi company’s vehicles freeze up, triggering traffic nightmares and blocking streets.

Three Waymo executives fielded questions during a hearing Monday by the San Francisco Board of Supervisors. The hearing comes after supervisors also questioned PG&E about the outage.

Sergio Quintana has more in the video above.