https://medium.com/@kyle.vogt/why-testing-self-driving-cars-in-sf-is-challenging-but-necessary-77dbe8345927

Anyone who has visited San Francisco knows driving here is kind of ridiculous. Our vehicles encounter challenging (and often absurd) situations up to 46 times more often than other places self-driving cars are tested. Perhaps for this reason, nobody else is regularly testing self-driving cars in SF. And while we’re generally drawn to tough problems, we test in SF only because we have to. We believe it’s the fastest path toward deploying self-driving cars at scale.

Our path to scale starts with fleet deployments in the most dense urban environments, where high utilization rates generate sustainable unit economics even at low initial vehicle volumes. As we ramp up volume, we’ll drive down costs and gradually roll out our technology to suburban and rural areas where ride sharing is less common today. It takes scale in order to reach these areas and achieve a significant impact on society, so for us anything less than that is failure (and probably an unsustainable business).