Waymos crash less than human drivers

This statistic could be misleading, because not all miles are equally dangerous. Google is very careful about selecting where it deploys and tests Waymo, preferring flat, safe, well-designed areas. Routing is also closely monitored and I would imagine that problematic roadways are avoided. The article says they compared it to human accident rates "on the same roads" but doesn't clarify their methodology for "same"ness. It also doesn't factor in driver experience. A taxi driver who has memorized a particular route is likely going to drive safer than a tourist who has never gone on that same road before. Waymo may be safer than the average driver on X road but that doesn't mean it will have the same comparative performance if you drop it onto a random road it has never driven before with no assistance from human support staff.

> The article says they compared it to human accident rates "on the same roads" but doesn't clarify their methodology for "same"ness.

Reading your comment before the article, my first thought was that "on the same roads" must mean literally the same roads - right?

But the article actually says:

> Using human crash data, Waymo estimated that human drivers on the same roads would get into 78 crashes

I agree that this is unclear. What data did they use, and why did they have to estimate at all? Shouldn't they be able to get the actual data for how many human drivers got into such accidents on this same exact set of roads over this same exact time period?