Waymo told TechCrunch that they are working on the citations, which can occur for various reasons, such as when the vehicles are waiting for their next customer and briefly park in an illegal zone. They also may sometimes stop in commercial loading zones to drop off customers.

The driverless cars picked up 589 parking tickets in San Francisco and 75 in Los Angeles last year, according to a Washington Post investigation.

San Francisco is a hot spot for Waymo vehicles, which operate without a human driver, but it seems the cars don't always play by the rules.

Waymo now has more than 300 driverless vehicles zipping passengers around San Francisco, but while they follow traffic laws, parking is another matter