I've heard New York is the only city in the US with excellent public transport. But yes, a proper underground metro requires a fair bit of planning and coordination, and if SF can't manage that then it will eventually end up like LA.
NYC's is on the order of Paris of London by way of comparison.
Washington D.C. (within the city) is a bit like a second tier European city, still quite good within the city, but D.C. has a huge metro area and it's spotty in the outer bits. There's lots of different jurisdictions that don't always integrate their bus systems well and building out the metro system has been slow going.
Portland has an excellent integrated system.
Chicago, Seattle, Boston, have decent, but limited systems.
However, even in places with almost no effective rail system, like Orlando, there's usually a comprehensive public bus system. They just run slowly, but they're relatively cheap, transfers are usually free and will get you close to where you want to go. Most public transport in L.A., for example, consists of the bus system.
I don't necessarily mean public transportation. Any transportation. Employer-provided buses, cabs, rickshaws, or even just roads where you can drive your own vehicle. Whatever is appropriate.
But the only thing that really works is underground carriage transport, because:
-It being underground means it's not in the way of everything and, more importantly, vice versa - it can go as fast as you want.
-It being carriage based means there's no coordination with other drivers. No queue dynamics, crossings or whatever. Transport happens in constant time, independent of the amount of passengers (within reasonable bounds).
I think rush hour travel on NYC's subway might put your "transport happens in constant time for grade separated trains" notion to the test. New York City's subway system is quite impressive, given that it's pushing 100 years old in many places and runs (nearly) 24/7/365, but the more crowded the subway gets -> the longer the doors take to close -> train headways become unevenly spaced -> queueing dynamics come into play. The latest "subway etiquette" ad campaigns from the operators specifically instruct riders to stand aside before boarding the train. [1] NYC rush hour is probably right on the edge of the "reasonable bounds" you are describing.
Most of the underground systems I have been on go pretty slow, and stop frequently. Pedal bike is the fastest way for me as long as you don't are willing to bend the rules (which in my opinion often make cycling more dangerous).
