I’ve written a lot about urban rail construction costs per kilometer, but from time to time, my colleagues and I have been asked about what happens if we compare costs, not per kilometer, but per rider. There’s an intuition among people in transportation advocacy (including anti-transit activists who prefer cars) that the construction costs of urban rail lines per rider are a meaningful measure of cost-effectiveness. This intuition is true, and yet, it must be interpreted delicately.
First, modes of transit with different operating cost structures should tolerate different levels of capital costs; in particular, the current practice in which subways are built at higher cost per rider than light rail, which in turn is built at higher cost than bus lanes, reflects real differences in operating costs and does not mean there is overinvestment in subways and underinvestment in buses. And second, costs per rider can be too low, in a sense – if a city’s construction costs per rider are very low, indicating a very high benefit-cost ratio, then it shouldn’t be lauded for its fiscal prudence but scolded for not having built these lines long ago and for not building more today. In truth, places with healthy decisionmaking about infrastructure expand their networks to the limit of cost-effectiveness, which means that costs per rider averaged over an entire region vary less than costs per kilometer, and this just reflects that cities build what they can, so low-cost cities can afford to build lines to lower-ridership areas, which higher-cost cities would reject as too expensive for the benefit. This way, costs per rider are not too different in New York and in cities that build for an order of magnitude lower cost per km than New York.
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