At one time Baltimore worked long and hard, and spent a lot of money, building a subway system. When the system was done, a prof I knew did a cost-benefit anal

At one time Baltimore worked long and hard, and spent a lot of money, building a subway system. When the system was done, a prof I knew did a cost-benefit analysis and looked for an optimal way to proceed. His result, clear and solid: Brick up the entrances to the subway and otherwise just f'get about it. That is, even given the subway already built and for free, just the continuing operating costs would exceed any reasonable list of benefits. The idea of cost-benefit analysis goes way back to the early 1900s: People saw that could have water resource projects that would let a desert bloom. So, there were a lot of such proposals. So, to filter the proposals people worked out the technique of cost-benefit analysis and wrote into some laws that for any such water projects the benefits had to exceed the costs -- that requirement filtered out nearly all the water projects. Subways and trains stand to be filtered similarly.