This does bring up an interesting question though -- does self driving doom mass transit? The answer is no -- the real ultimate benefit of mass transit that taxis can never replicate is _thoroughput_ in a dense area. Articulated buses or light or heavy rail are the only way you could ever service an area like Manhattan, because even with high occupancy, using just sedans would require the building of like, literally 50 more highways. A single lane of train/bus can do the work of dozens of car lanes and nothing can change that physical law.
Self driving buses will reduce the price slightly though. And importantly, people today often drive because of the "last mile" problem. Driverless taxi on the other hand, may make it much easier to connect to mass transit seamlessly. You could even connect more than once. I could get from suburban Queens to the suburbs of Philadelphia by taking a taxi to the train station, a train that is faster than cars due to traffic, then another taxi on the other end, seamlessly. Actually I can do that today, it will just be cheaper, that's all. So more people will do it.
> the real ultimate benefit of mass transit that taxis can never replicate is _thoroughput_ in a dense area
But what if in the far future people stop owning cars and so everyone is hailing a self driving car? Perhaps then there would be enough people that you would almost always carpool? Would buses still be necessary then? I'm sure they'd still make sense in some cases but I can also see some bus stops being replaced
Yes, they still would in places like Manhattan and Tokyo, but you're right that they wouldn't be necessary in many other high but still not super high density places.
Even assuming 4 people to a sedan, the space needed for the engine and the safe following distance makes the density very low compared to a bus/train that is long and can have people standing packed in.
4 people to a sedan only gives you a factor of 4 improvement, which is just not enough for places like Manhattan or Tokyo. They would still need to build a dozen down from like 50.
You can't live anywhere near a BART station, let alone a few hundred feet, without losing any sort of discount with mass transit... Not to mention the vast majority of the metropolitan Bay Area is miles away from BART.
There's a big difference between 100ft to the nearest road vs 5 miles to the BART station. Last mile transportation is important, even if constrained to fully mapped roads.
