Waymo marks a major self-driving milestone

Waymo's autonomous cars have steadily rolled through test routes in multiple states over the past few years, and now the company claims it has passed a new milestone: 4 million self-driven miles logged on public roads.

That makes the Waymo fleet the most experienced autonomous car platform currently on the road, according to the company, which says the average American driver would take 300 years to hit the same mark.

While the number is arbitrary to a degree, the progress it represents is essential to Waymo's mission to create truly driverless cars. The AI behind the platform needs to be trained in real-world situations to understand how to react to every potential condition it might face, so the more test miles it logs, the better.

The Google spinoff says its fleet of test vehicles drove the last million miles in just six months, a rapid improvement from the 18 months it took to accumulate the first million (from the first public test). Some of that progress can likely be attributed to improvements to the platform, which make it easier to take the vehicles into more complicated traffic scenarios — but Waymo can also likely thank the local authorities in testing areas like Phoenix for helping it to expand its programs from the pilot's early days in 2015.

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Waymo also claims it simulated an additional 2.5 billion miles in the last year alone, which help train the cars' AI without putting vehicles on the road.

The milestone comes as Waymo preps to expand testing, introducing some of its fleet to Michigan for trials in hazardous cold weather conditions and rolling out the first truly driverless test vehicles to the public in Phoenix. These programs will likely play a part in making the next million test miles an even quicker accomplishment than the last, bringing Waymo even closer to introducing a mature self-driving platform for the public's use.