By: Nick Gambino
When you see a fleet of self-driving cars weaving through the streets, you’d never think a city-wide power outage would cause those cars to shut down, but that’s exactly what happened to Waymo vehicles last week in San Francisco.
The blackout caused a third of the city to go dark, playing hell at intersections, but while traffic lights were down, cars driven by humans, of course, didn’t shut down with them. Waymo self-driving cars on the other hand were dead where they stood.
It seemed the lack of traffic lights crippled the cars’ ability to “think” and navigate. At least that’s what it looked like. Now we have an official explanation from Waymo on the incident.
“While the Waymo Driver is designed to handle dark traffic signals as four-way stops, it may occasionally request a confirmation check to ensure it makes the safest choice,” a Waymo blog post reads. “While we successfully traversed more than 7,000 dark signals on Saturday, the outage created a concentrated spike in these requests. This created a backlog that, in some cases, led to response delays contributing to congestion on already-overwhelmed streets.”
These confirmation checks were programmed into Waymo cars as a sort of checks and balances thing, but it was never meant to handle a blackout of this magnitude. And because the system is still built on manual human confirmation, there’s no way they could keep up with the number of requests coming in.
That’s why Waymo is making changes to more closely reflect the scale of their self-driving fleet today. These autonomous vehicles have traveled over 100 million miles to date and need to be fully automated to meet the demands of the workload, though it’s not clear that they’ll be automating the confirmation request going forward.
The new system will still see the cars navigating downed traffic lights as four-way stops, but it will receive data about local power outages and use that information to make better decisions.
I can’t imagine what a prolonged city-wide blackout would look like in a location where there are thousands and thousands of self-driving cars. Last weekend in San Francisco was a taste of that, but hopefully these new protocol changes will help.
