Waymo, the self-driving car company under Alphabet, has been testing in the suburbs of Phoenix for several years now. And while the sunny metropolis might seem like the ideal and easiest location to test autonomous vehicle technology, there are times when the desert becomes a dangerous place for any driver — human or computer.

The two big safety concerns in this desert region are sudden downpours that cause flash floods and haboobs, giant walls of dust between 1,500 and 3,000 feet high that can cover up to 100 square miles. One record-breaking haboob in July 2011 covered the entire Phoenix valley, an area of more than 517 square miles.

Waymo released Friday a blog post that included two videos showing how the sensors on its self-driving vehicles detect and recognize objects while navigating through a haboob in Phoenix and fog in San Francisco. The vehicle in Phoenix was manually driven, while the one in the fog video was in autonomous mode.

The point of the videos, Waymo says, is to show how, and if, the vehicles recognize objects during these extreme low visibility moments. And they do. The haboob video shows how its sensors work to identify a pedestrian crossing a street with little to no visibility.

Waymo uses a combination of lidar, radar and cameras to detect and identify objects. Fog, rain or dust can limit visibility in all or some of these sensors.

Waymo doesn’t silo the sensors affected by a particular weather event. Instead, it continues to take in data from all the sensors, even those that don’t function as well in fog or dust, and uses that collective information to better identify objects.

The potential is for autonomous vehicles to improve on visibility, one of the greatest performance limitations of humans, Debbie Hersman, Waymo’s chief safety officer wrote in the blog post. If Waymo or other AV companies are successful, they could help reduce one of the leading contributors to crashes. The Department of Transportation estimates that weather contributes to 21% of the annual U.S. crashes.

Still, there are times when even an autonomous vehicle doesn’t belong on the road. It’s critical for any company planning to deploy AVs to have a system that can not only identify, but also take the safest action if conditions worsen.

Waymo vehicles are designed to automatically detect sudden extreme weather changes, such as a snowstorm, that could impact the ability of a human or an AV to drive safely, according to Hersman.

The question is what happens next. Humans are supposed to pull over off the road during a haboob and turn off the vehicle, a similar action when one encounters heavy fog. Waymo’s self-driving vehicles will do the same if weather conditions deteriorate to the point that the company believes it would affect the safe operation of its cars, Hersman wrote.

The videos and blog post are the latest effort by Waymo to showcase how and where it’s testing. The company announced August 20 that it has started testing how its sensors handle heavy rain in Florida. The move to Florida will focus on data collection and testing sensors; the vehicles will be manually driven for now.

Waymo also tests (or has tested) its technology in and around Mountain View, Calif., Novi, Mich., Kirkland, Wash. and San Francisco. The bulk of the company’s activities have been in suburbs of Phoenix and around Mountain View.