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Yes, they are assuming a best-case scenario. Driverless systems are very expensive for reasons that have little to do with the cost of the driverless trains, if you're not going to consider those variables this kind of armchair speculation is a waste of everyone's time.

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They aren't though? If you're building a new line, fully driverless is pretty much the default these days, especially if the line is fully underground or elevated.

What is incredibly expensive, though, is retrofitting a line designed for manual operation to run automatically instead.

Well, a lot of systems exist that were initially designed for automatic operation but still end up becoming operated manually or partially manually due to safety concerns or politics. Washington DC Metro and BART are the two big systems I can think of that had this issue.

Both examples of Great Society metros that were on the bleeding edge of what was possible in the early 70s. Automatic train control advanced rapidly, with both Vancouver SkyTrain and London Docklands Light Rail being built in the 80s and operating driverless for their entire existence.

DC Metro just recently re-enabled full automatic train operation across all the lines in June.

I see

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