Google's Waymo Tests ‘Critical Miles' in Detailed Virtual Cities

Author: Michael Cheng   

Ever wonder how Google's Waymo prepares, stimulates and tests its growing fleet of autonomous vehicles?

The company recently provided a preview of its testing sites and procedures, which takes place in a virtual stimulator and a fake city.


For Waymo, virtual testing of driverless systems is conducted using Carcraft – the company's autonomous driving stimulator. According to developers, around 25,000 stimulations are ongoing in the virtual world, which consists of scaled versions of real cities. This method of testing is particularly beneficial for stimulating extremely dangerous scenarios, such as testing reactions to falling objects when driving on the side of a slippery cliff. It would be too hazardous and costly to perform such exercises in live environments.

Furthermore, engineers could easily replay the same scenario over and over again without needing to spend time on physically setting up key elements of the stimulation.

"At any time, there are now 25,000 virtual self-driving cars making their way through fully modeled versions of Austin, Mountain View, and Phoenix, as well as test-track scenarios," highlighted Alexis Madrigal from The Atlantic. "Waymo might simulate driving down particularly tricky road hundreds of thousands of times in a single day. Collectively, they now drive 8 million miles per day in the virtual world."

The Castle

For testing in live environments, Waymo developers take their fleet of driverless cars to an old Air Force base in California. The 100-acre site is a massive mockup of existing cities around the US. Engineers can customize specific parts of the area for testing. For example, if developers want to test a new sensing component that detects domesticated animals around neighborhoods, it could deploy moving figurines around intersections to stimulate random street crossings.

Equipped with a rain stimulator, the site sits north of the Merced metro area. The company pays $19,000 per month for rent, which is part of a two-year lease. It takes roughly 2.5 hours to get to the facility from Google's headquarters. At the site, Waymo is using the following prototypes: customized Lexus, retired Prius and Chrysler Pacifica minivans. This is also where the business is trialing its SAE-L4 autonomous driving platform.

There are no real buildings at the Castle. The facility features one structure for operators to rest if they are unable drive back home after a long day (or night) of binge testing.

"We made conscious decisions in designing to make residential streets, expressway-style streets, cul-de-sacs, parking lots, things like that, so we'd have a representative concentration of features that we could drive around," said Steph Villegas, who oversees operations at the Castle.

Impressively, Waymo has completed over three million miles around the Castle test site. Of course, this is nowhere near the two billion miles logged in the Carcraft stimulator. However, there are some aspects to live testing that makes such accomplishments noteworthy. Accruing three million 'live' miles requires a lot of gas (or battery power), as well as maintenance. Moreover, it is important to highlight that data from virtual miles accumulated on Carcraft is fed into the same platform used by self-driving cars at the Castle. 

Michael Cheng
Michael Cheng is a legal editor and technical writer with publications for Blackberry ISHN Magazine Houzz and Payment Week. He specializes in technology business and digesting hard data. Outside of work Michael likes to train for marathons spend time with his daughter and explore new places.
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