How Cruise vehicles return to the garage autonomously in heavy rain

Their autonomous vehicles and operations team work together to handle heavy rain.

16 Jan 2023

Cruise doesn’t carry passengers in heavy rain. The operational design domain (ODD) in their CPUC permit (PDF) only allows services in light rain.

I’ve always wondered how they implement this operationally. For example, Waymo preemptively launches all cars with operators in the driver’s seat anytime there’s rain in the forecast. Cruise has no such policy: I have never seen them assign operators to customer-facing vehicles.

Yet Cruise claims to run up to 100 driverless vehicles concurrently. It would be impractical to dispatch a human driver to each vehicle whenever it starts raining. When the latest atmostpheric river hit San Francisco, I knew it was my chance to find out how it worked.

Monitoring the Cruise app

As the rain intensified, as expected, all cars disappeared from Cruise’s app and the weather pause icon appeared.

A screenshot with a map and the message: We'll be back when a car becomes available. A screenshot with a map and the message: We'll be back when the weather clears.

But then something unusual happened. The app returned to its normal state. A few cars showed up near a hole in the geofence — and they were actually hailable.

A screenshot of a map with three cars in close proximity. A screenshot of the trip plan. Car arriving in 39 minutes.

Visiting the garage

I drove over to find that this street is the entrance to one of Cruise’s garages. The same location has been featured in Cruise executives’ past tweets promoting the service.1

Despite the heavy rain and gusts strong enough to blow my hat/jacket off, a steady stream of Cruise vehicles were returning themselves to the garage in driverless mode.

Two vehicles turn into a driveway

Driverless Cruise vehicles enter the garage during heavy rain.

A person enters the driver's door of a vehicle

A member of Cruise’s operations team enters the vehicle to drive it into the garage.

In total, I observed:

Two vehicles skip the garage

After the first six driverless vehicles returned, the next two kept driving past the garage. I followed them in my own car. They drove for about 16 minutes, handling large puddles and road spray without noticeable comfort issues. Eventually they looped back to the garage and successfully entered.

An autonomous vehicle turns right at an intersection, kicking up water from a puddle

A Cruise vehicle drives through a puddle during its detour.

I’m not totally sure what happened here. I can think of two reasonable explanations:

  1. Boring: The cars missed the turn for some unknown reason.
  2. Exciting: Cruise has implemented logic to avoid overwhelming the operations team’s ability to put cars back in the garage. If there are too many vehicles waiting to return, subsequent cars take a detour to kill time instead of blocking the driveway.

Key take-aways

  1. I can’t find the timelapse of Cruise launching their driverless cars anymore. I’m pretty sure it was posted to Twitter. Please let me know if you have the link! Update: Link to tweet by @kvogt

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