"presuming [robocars are] a tech which gets [an] adoption curve similar to the late-20th century curves of new computer related technologies. That is not a small claim"
Indeed, I think you are being overoptimistic by several degrees. We in high tech are used to this pace of change, and as science fiction fans, as well, we have visions of things we feel we know are surely just over the horizon. Then we run into the reality of the sargasso of multiple layers of city, state, and federal politics, plus opposition from existing entrenched industries, public opinion that is influenced by that opposition, other overoptimistic projections by private contractors and suppliers, etc.
"I do expect decent robotaxi services to start showing up reasonably early on"
I do as well, though I fear the opposition from existing cab companies and drivers as much as I fear opposition to self-driving busses and trains from transit drivers' unions. The cab companies are just as perniciously entrenched in municipal politics, and they are already facing disruption from things like Uber, so they have more forewarning and have more time to prepare for further threats like robotaxis.
"$1/mile taxi outcompetes transit trips"
Chasm jumping again. This is not near-term, and it requires many things to fall together into place just-so. (What was it you were saying before about complicated vs. dumb systems?) It also presumes the roads being able to handle the increased usage that would come with robotaxis being cheaper than transit. And it presumes that pricing wouldn't be affected by both peak pricing, which is more easily applied to robotaxis than transit, and congestion charges, which are similarly much more easily applied to robotaxis than to private vehicles.
You say "Fully packed trains at rush hour" and yet in your next paragraph you say "Trains can actually do even better numbers than you say." Indeed, I even mentioned I was describing the LOW end of capacity, and yet your counter-argument implies "cream skimming."
"BRT (which should become Bus+conformant robot lanes)"
We totally agree, there. The synergy should be obvious to all.
"[trains only] serve a limited population that lives and works along them."
But again, robocars and trains have synergies, here!
- Quick and easy first- and last-mile robocar trips to and from nearby transit stations
- No need to park-and-ride
- No need to walk to a bus stop, to wait for a bus, to get you to the train
- Quick and easy train station-to-destination travel at the other end of your train trip
- On-demand personal vehicle access during the day while at your destination, so you don't need to worry that you won't have your own car available if you take the train
- Faster travel, over a longer distance, at a lower price than either personal cars or robotaxis, with almost the same amount of convenience
- None of the hassles of needing to find (in a self-driving car) and/or pay for (for both self-driving cars AND personal robocars) parking at your destination
- No need to own a car in a city to reverse-commute to some suburbs (e.g. Silicon Valley)
- Weekend recreational trips can be done with a cheaper, faster train for part of your trip and then you hire a robocar to drive around at your destination
- Easy mixed-mode trips with transit in one direction and a robocar in the other (or multi-point mixed-mode travel), bringing back cargo, visitors with their luggage from airports, etc.
Over longer distances the synergies are clear, but long distance trains don't only have stations at the ends, they also have stations in the middle. This means long distance trains are also short distance ones for some people. Transit corridors remain highly valuable, useful things.
Robocars are actually more likely to increase than decrease the desirability and demand on non-local mass transit in the near term, increasing its efficiency.
"the ability of robocars to replace the big mass transit systems is more distant"
Presumption of desirability and feasibility. "More distant" may be asymptotically so. In the meantime the impression I get is that you're picking unnecessary fights with transit people by implying that one will replace the other.
"mass transit is only really efficient ... at rush hour"
...in the suburbs.
And you said yourself that peak transit time isn't even rush hour, it's at lunch hour. In urban areas "peak" transit time is all throughout the day, with a few early, mid, and late spikes (which is why I try to avoid using the term "rush hour" rather than the broader "peak time").
"there will be resistance to buying transit equipment to use only a few hours/day..."
10 to 12+ hours a day in cities. (7am to 6pm? Yeah.)
Also, the economics are different if you're starting from scratch and buying all your equipment than if you're talking about places where there are already existing transit services and infrastructure, ROW is already owned, some land such as park-and-ride lots and employee parking can be repurposed, etc.
"...and hiring staff who only work rush hour."
As I said before, the same robocar tech can and surely will be applied to transit vehicles, as well, reducing payroll, insurance, pensions, etc. Yes, there will be transit union opposition. However, as I said above, there will similarly be cab company and cab driver opposition to robotaxis. I'd say that's a wash.
"Commuter rail ... is the most efficient form of transit in the US"
Ironically operating on a ROW that is either dedicated, or shared only with non-passenger carrying freight trains. :)