I crunched the math on this a little while back as a fun exercise:<p>To replace a single rush-hour NYC subway train with all single-occupancy vehicles, based on the average length of car in the US, would occupy every lane in a single direction on Market St in San Francisco from the waterfront all the way to Van Ness.<p>In other words, in order to get a subway train full of people into the city, but in cars instead, the lineup of cars (spread over multiple lanes!) would stretch the entirety of downtown SF. And this assumes perfect packing - i.e., bumper to bumper.<p>Side note: I&#x27;m quite optimistic about self-driving cars, but it never ceases to amaze me how many self-driving car proponents seem to be utopian futurists who are entirely reality-resistant. No, self-driving pod cars will not produce greater capacity than a heavy rail mass transit network, are you even serious. They may very well become a key fixture of our transportation infrastructure, but there is simply no physical way fleets of taxibots will ever rival the throughput of a NYC subway train at rush hour.