Bus is cheaper than rail. Paint is cheap. Rail only made sense a hundred years ago when construction costs were lower. Trains have no inherent advantage over buses. It doesn’t cost more to operate a bus than to operate a train. All of those are true in specific sets of circumstances, and Curitiba and Bogota deserve a lot of credit for recognizing that in their case they were true and opting for a good BRT system. Unfortunately, the notion that buses are always cheaper than trains has turned into a mantra that’s applied even far from the original circumstance of BRT.

The advantage of buses is that dedicating lanes to them and installing signal priority are financially cheap, if politically difficult in the face of opposition from drivers. Even physically separating those lanes is essentially cost-free. This advantage disappears completely when it comes to installing new lanes, or paving an existing right-of-way. Hartford is paving over an abandoned railroad at a cost of $37 million per km.

Not to be outdone, New York’s own MTA just proposed to pave about 8.5 km of the Staten Island Railway’s North Shore Branch for $371 million. A light rail alternative was jettisoned because the MTA insisted on continuing the line to the West Shore Plaza, along what is possibly the least developed road in the city.

Another, related mantra is that light rail is cheaper than heavy rail. This contributed to the MTA’s decision not to pursue a Staten Island Railway-compatible solution, which would allow lower capital costs and cheaper maintenance since trains could be maintained together with the existing fleet without modifying the existing yard. As with all mantras, this one has a kernel of truth: it’s much cheaper to build on-street light rail than elevated rail or a subway. As with the BRT mantra, this is not true when the discussion is about what to do in an existing right-of-way.

Worse, because the MTA believed its own hype, it completely missed the point of surface transit. People who believe these mantras about bus, light rail, and heavy rail can easily miss the advantage of on-street running wherever the streets are more central than the railroad rights-of-way. The North Shore Branch hugs the shore for much of the way, halving station radius. The most developed corridor is Forest Avenue, hosting the S48, the third busiest bus in the borough and the busiest in the same area and orientation as the line in question. (The busiest in the borough, the S53, crosses the bridge to connect the North Shore to the subway in Brooklyn.) Of the three other east-west routes in the North Shore, the one that the North Shore Branch parallels the most closely, the S40, has the lowest ridership. It would be both vastly cheaper and better for bus riders to have dedicated bus lanes on Forest, or possibly Castleton, which hosts the S46.

In cities that did not develop around mainline rail corridors but rather around major streets, the only reason to use mainline rail corridors for urban transit is that reactivating them for rail can be done at much lower cost than building on-street light rail. New York is for historical reasons such a city: Staten Island development follows Forest and Castleton rather than the North Shore Branch, and for similar reasons Park Avenue in Manhattan and the Bronx is a relatively unimportant commercial corridor.

Now, these mainline corridors have great use for regional transit. Queens Boulevard can’t be easily used for train service to Long Island, and Lexington Avenue can’t be easily used for train service to Westchester. Staten Island has great potential for regional transit – but only if it’s electrified rail going through a tunnel to Manhattan. It’s expensive, but it’s what it takes to be time-competitive with the ferry and with buses to the subway. A more competent agency than the MTA would keep planning and designing such high-cost, high-benefit projects, to be built in the future if funding materializes; such plans could also be used to concretely argue for more funding from the state and from Congress.

Instead, the MTA is spending more money than most light rail lines cost, to make such a mainline connection from the North Shore to Manhattan impossible in the future. The best scenario in such a situation is that the busway would have to be railstituted, for a few hundred million dollars – an embarrassing reminder of the busway folly, but still a much smaller sum than the cost of the tunnel. The worst scenario is that like on Los Angeles’s Orange Line, the need to keep buses operating during construction would make it impossible to replace them with trains.

There aren’t a lot of lose-lose (or win-win) situations with transportation, even if we ignore driver convenience, but this is one of them. It’s a fiscal disaster relative to predicted ridership and the operating costs of buses, it makes future transit expansion in the borough more difficult, and it follows a marginal route. All this is so that the MTA can say it’s finally making use of an abandoned right-of-way.