Waymo's self-driving car prototype. Business Insider/Biz Carson When it comes to self-driving cars, an old adage still holds true: it's quality, not quantity.

Google has been developing its cars since 2009 and one of its favorite stats to share about the project is that its self-driving cars have driven over 2 million miles. Google, which spun out its self-driving car unit into an independent company called Waymo last week, wrote on the Waymo website that the cars now have "the equivalent of over 300 years of human driving experience, largely on city steets."

That kind of mileage shouldn't be taken lightly — Google's cars are extraordinarily perceptive and can recognize objects that can be difficult for self-driving cars to see, like bicycles.

But at a time where Google is feeling growing pressure from competitors like Uber and Tesla, the tech giant has yet to test its self-driving cars in cold weather or snowy conditions. As anyone hailing from the East Coast or Midwest can attest, driving in snow is a required skill.

Snow and its challenges

Snow poses a particular set of challenges for self-driving cars because it can confuse the systems they rely on to get around, like cameras and lidar, a sensor that uses lasers to map the car's surroundings so it can "see" the world.

When there's snow on the ground, cameras and lidar have a difficult time seeing lane markers, which cars rely on to prevent lane drift and navigate safely. Snow can also make it more difficult to detect unexpected obstacles.

"Heavy snow and rain tend to confuse lidar sensors and also cameras," John Dolan, principle systems scientist at Carnegie Mellon's Robotics Institute, previously told Business Insider. "So you end up having some problems."

Automakers and startups investing in self-driving cars have generally been forthcoming about the challenges posed by snow fall and how they are planning to address them.

Last January, Ford successfully tested one of its self-driving cars in the snow for the first time.

"It’s one thing for a car to drive itself in perfect weather, it’s quite another to do so when the car’s sensors can’t see the road because it’s covered in snow," Jim McBride, Ford technical leader for autonomous vehicles, said at the time.

"Weather isn’t perfect, and that’s why we’re testing autonomous vehicles in wintry conditions – for the roughly 70% of U.S. residents who live in snowy regions," he continued.

Ford still has a long way to go to prepare for real snow conditions — the test didn't occur on public roads, but on its MCity testing site in Ann Arbor, Michigan. But considering Ford already has a campus in a state that frequently endures snow, it's better positioned than others primarily testing in states like California and Nevada.

General Motors announced last week that it will begin testing its self-driving cars in Michigan as its primary cold weather testing site. Michigan became the first state to pass regulations for the testing, use, and eventual sale of self-driving cars in early December, giving GM the chance to test near its Tech Center in Warren, Michigan, GM CEO Mary Barra said at the time.

Barra has been vocal about the importance of testing in a variety of conditions, rather than focusing on the actual mile count.

"A lot of the conversation has been about, 'Oh, we have this many miles,' but it's not as much about the miles as it is about the experiences that the car learns," she told Business Insider's Cadie Thompson.

Even Uber has said it's preparing its cars for extreme weather conditions in Pittsburgh, the location of its first pilot program that was launched in September.

But Google has yet to make any announcement about testing in cold weather and snow.

Google and the competition

Waymo CEO John Krafcik AP Google currently tests its cars in Mountain View, California; Metro Phoneix, Arizona; Austin, Texas; and Kirkland, Washington.

In Google's defense, those testing sites do allow the cars to get unique driving experiences that others may be lacking. For example, Google wrote in its August monthly report that testing in Arizona allows the cars to get accustomed to dusty conditions and extreme temperatures.

Google has also noted that its Washington test site gives the cars some experience driving in heavy rain.

But Google has yet to pick a location to prepare the cars for snow, ice, and extremely cold temperature. John Krafcik, CEO of Google's Waymo, said in a July Bloomberg interview that "serious snow testing" is still to come.

Google did not return Business Insider's request for comment.

All of this is to say that even though Google got a head start by launching its self-driving car project in 2009, it still has a lot of testing to accomplish before its cars are ready for the majority of the United States.

That's not to say Ford, GM, or Uber don't have their work cut out for them, but GM and Uber started their self-driving car projects much later. (Uber was founded the same year Google launched its self-driving car project!) Ford, which begun its autonomous research program in 2005, is now testing in cold weather in addition to Arizona and San Francisco.

Google made a significant stride by spinning out its self-driving car unit into Waymo, but it still has yet to announce how it plans to get its self-driving tech to consumers. In the meantime, Google best prepare for snow.

The opinions expressed in this article are those of the author.