IIRC very few public transport systems make a profit on running costs - never mind capital costs. The rest operate as money pits.
Useful systems have huge positive externalities that can't be captured by charging passengers at a rate that reflects those benefits (I'm not sure if this is due to a free-loader effect, irrationality on the passengers part or something else).
I think the only systems that have profited on scale commensurate with their benefits are those that were a real estate play, eg.: the Metropolitan Line[1] in London, Los Angeles trams, Hong Kong subways. I might be wrong about these examples, either due to misremembering or to falling to a just-so story.
Edit 2: The point, I think, is that if you rely on direct profits for the transport system you give up on huge benefits and accept huge costs across society.
Useful systems have huge positive externalities that can't be captured by charging passengers at a rate that reflects those benefits (I'm not sure if this is due to a free-loader effect, irrationality on the passengers part or something else).
I think the only systems that have profited on scale commensurate with their benefits are those that were a real estate play, eg.: the Metropolitan Line[1] in London, Los Angeles trams, Hong Kong subways. I might be wrong about these examples, either due to misremembering or to falling to a just-so story.
[1] https://en.wikipedia.org/wiki/Metro-land
Edit: formatting.
Edit 2: The point, I think, is that if you rely on direct profits for the transport system you give up on huge benefits and accept huge costs across society.