Our self-driving vehicles need to operate reliably and safely in all sorts of conditions, whether sun or snow, extreme cold or oppressive heat. Because we develop both our self-driving hardware and software in-house, Waymo’s engineers are able to design a complete system that can work reliably in the toughest environments.

In early spring, our self-driving minivans visited Lake Tahoe during record snowfall. Now, we’re tackling the other end of the temperature spectrum. After a three-day road trip from Davis Dam to Las Vegas, we took our new self-driving Chrysler Pacifica Hybrid minivans — equipped with all our latest sensors — to one of hottest places on Earth, Death Valley, California. We caught up with Simon, a Waymo senior thermal engineer, on the road.

Why is it important to test Waymo’s self-driving cars in extreme heat?

This type of testing is standard in the automobile industry. But when you add self-driving systems to a car — which generate their own additional heat — conducting rigorous testing to ensure your systems can withstand high temperatures is even more important. If you’ve used your cell phone in the bright sun on a hot day you may have experienced it shutting down. Our self-driving system needs to be much more reliable than your typical home electronics. This type of testing allows us to be confident our vehicle can cool itself and continue to operate under the hottest temperatures, even with an engine running at full power and our systems running at full capacity.

What goes on when heat testing a self-driving car?

We’ve been heat testing our latest Chrysler Pacifica cars for almost a year, starting with what’s called a drive cell, or aerothermal wind tunnel. Using the drive cell we can mimic almost any weather condition, including the hottest temperatures ever recorded in the country. After extensive testing in this controlled environment we’re then ready to put our cars through their paces on public roads.

The goal for this trip was to run our cars in as many driving conditions as possible, all in extreme heat. That means stop-and-go traffic, idling for long periods of time, sloped roads, and more. In testing we closely monitor our systems by taking over 200 different measurements per second in order to confirm our in-house sensor suite continues to function as intended. As well as ensuring our vehicles are happy in all that heat, we keep an eye on cabin temperature so our passengers will be comfortable too.

Our self-driving Pacifica minivan on the Las Vegas Strip.

Why did you choose three different locations to conduct heat testing?

Each offered a different, but important, environment to learn from. The Davis Dam, which is on the Arizona and Nevada border, has long stretches of steep desert road for us to drive under the hot sun. The Las Vegas Strip gave us countless busy lanes of endless traffic to choose from, all under intense heat (as well as the intense gaze of crowds of onlookers).

And here in Death Valley we see some of the highest recorded temperatures in the country, particularly in the aptly-named Furnace Creek. In fact, Furnace Creek holds the record for the highest officially recorded temperature on Earth: 134°F on July 10, 1913. While I’ve been spared those temperatures, I can confirm it’s uncomfortably hot. You know you’re in a real desert when the soles of your shoes start to melt and stick to the ground like chewing gum!

Simon, Waymo’s senior thermal engineer, behind the wheel in Death Valley.

What did you learn from testing?

Our testing confirmed the results of our drive cell work: our hardware is road-ready for extreme heat. By pushing our car to its limits in testing, we can rest assured that no matter where our riders choose to drive — even if that’s in the middle of the desert, on a sunny day, with the air conditioning on full blast — Waymo’s cars will still be able to get them where they need to go.