Since the 2015-9 capital plan, the New York MTA had been including the second phase of Second Avenue Subway in its capital plan, without a clear estimate of its projected cost. The rumors said the cost would be about $5 billion. A new media story finally gives an official cost estimate: $6 billion. The total length of the project, from 96th Street and 2nd Avenue to 125th Street and Lexington, is about 2.7 km. At $2.2 billion per km, this sets a new world record for subway construction costs, breaking that of the first phase of the same line, which only cost $1.7 billion per km. See a compendium of past posts here to look how these projects stack up. For people not interested in combing through multiple old posts of mine, the short version is that outside the Anglosphere, subway tunnels typically cost $100-300 million per km, with outliers in both directions, but even inside the Anglosphere, costs are in the mid-to-high hundreds of million per km.

In some way, the high cost of SAS phase 2 is more frustrating than that of phase 1. This is because 1 km of the 2.7 km of route preexists. SAS construction began in the 1970s, but was halted due to New York’s financial crisis. In East Harlem, some actual tunnel segments were dug, roughly between the proposed station locations at 96th, 106th, 116th, and 125th Streets; Wikipedia has a more detailed list. Construction of phase 2 thus involves just the stations, plus a short bored segment under 125th Street to get from Second Avenue to Lexington, for a connection to the 4, 5, and 6 trains.

Not having to build tunnels between the stations is beneficial, not as a cost saver in itself but as a way to reduce station costs. In phase 1, it appears that most costs were associated with the stations themselves; if I remember correctly, the cost breakdown was 25% for each of three new stations, and 25% for the tunnels in between. The reason is that the stations are quite deep, while the tunneling in between is bored, to reduce surface disruption. Deep stations are more expensive because they require more excavation, while tunnel boring costs depend more on soil type and how much infrastructure is in the way than on depth. Counting the extra expense of stations, bored subways cost more per km than cut-and-cover subways, but create less surface disruption away from station sites, which is why this method was chosen for phase 1. In contrast, in phase 2, most construction is stations, which would favor a shallow cut-and-cover solution.

Unfortunately, according to rumors, it appears that the MTA now judges it impossible to use the preexisting tunnels in phase 2. If this is true, then this would explain the higher cost (though it would justify $400 million per km, not $2.2 billion): they’d have to build underneath those tunnels. But if this is true then it suggests severe incompetence in the planning stage, of the kind that should get senior employees fired and consultants blacklisted.

The reason is that Second Avenue Subway was planned as a single line. The Environmental Impact Statement was for the full line, including the proposed construction techniques. The phasing was agreed on by then; there was only enough state money for phase 1. This isn’t an unexpected change of plans. I’d understand if in the 2000s it was found that tunnels from the 1970s were not usable; this happened further south, in phase 4, where a preexisting tunnel under Chrystie Street was found to be difficult to use. But in the 2000s the SAS studies signed off on using the tunnels in Harlem, and what seems to be happening is that phase 1, built according to the specifications of the same study, is too deep for using the tunnels.

At $6 billion, this line shouldn’t be built. I know that it goes to a low-income, underserved neighborhood, one that I’ve attacked New York before for taking years to equip with bike lanes (scroll down to my comments here). But the ridership projection is 100,000 per weekday, and $60,000 per weekday rider is too much. Phase 1, providing an underrated east-west connection and serving a denser neighborhood, is projected to get 200,000, for a projection of around $25,000 per weekday rider, which isn’t terrible, so it’s a justified project even if the costs could be an order of magnitude lower.

Were costs lower, it would be possible to build subways to many more low-income neighborhoods in New York. A 125th Street crosstown line, extending phase 2 of SAS, would provide Harlem with crucial east-west connectivity. Subways under Nostrand and Utica Avenues would serve a mixture of working- and middle-class neighborhoods in Brooklyn. A subway under Northern Boulevard in Queens, connecting to phases 3 and 4 of SAS, would serve one of the poorest parts of Queens. A network of tramways would improve surface transit in the South Bronx. Triboro Line would connect poor areas like the South Bronx and East New York with richer ones like Astoria. New York could achieve a lot, especially for its most vulnerable residents, if it could construct subways affordably.

But in a world in which subways cost $60,000 per weekday rider and $2.2 billion per km, New York cannot extend the subway. If it has money in its budget for investment, it should look into things other than transportation, such as social housing or schools. Or it could not borrow money at all to pay for big projects, and in lieu of the money spent on interest, reduce taxes, or increase ongoing social spending.

Given persistent high costs, I would recommend shelving SAS and future rail extensions in New York, including the Gateway tunnel, until costs can be drastically cut. There’s no shortage of worthy priorities for scarce budget in New York, both city and state. Health care in the US is too expensive by a factor of 2, not 10, and transfer payments have near-100% efficiency no matter what; it’s possible to exhaust the tax capability of a state or city just on these two items. Perhaps the need to compete with other budget priorities would get the MTA to cut waste.