It seems to be common wisdom that the subway in New York is at capacity. Last year, the New York Times ran an article that repeated the MTA’s claims that growing delays come from overcrowding (which they don’t). A few weeks ago the NY Times quoted Riders Alliance campaign manager Rebecca Bailin saying “Our system is at capacity” and “subways are delayed when people can’t fit in them.” So far so good: some parts of the subway have serious capacity issues, which require investment in organization and electronics (but not concrete) to fix. But then some people make a stronger claim saying that the entire system is at capacity and not just parts of it, and that’s just wrong.

A few days ago there was an argument on Twitter involving the Manhattan Institute’s Nicole Gelinas and Alex Armlovich on one side and Stephen Smith on the other. Stephen made the usual YIMBY point that New York can expect more population growth in the near future. Nicole argued instead that no, there’s no room for population growth, because the subway is at capacity. Alex chimed in,

People are not going to be willing to pay market rents for places they can’t commute from. A large number of folks underestimate the self-regulation of NYC housing–it just can’t get that bad, because people can always just move to Philly Like, if upzone Williamsburg, people who move into new housing aren’t going to try to ride the L–they’ll only come if they can walk/bike or ride in off-peak direction. Just like people are leaving in response to the shutdown. Neighborhoods and cities are in spatial equilibrium!

I responded by talking about rents, but in a way my response conceded too much, by focusing on Williamsburg. The L train has serious crowding problems, coming from lack of electrical capacity to run more than 20 trains per hour per direction (the tracks and signals can handle 26 trains, and could handle more if the L train had tail tracks at its 8th Avenue terminal). However, the L train is atypical of New York. The Hub Bound Report has data on peak crowding into the Manhattan core, on table 20 in appendix II. The three most crowded lines entering the Manhattan core, measured in passengers per floor area of train, are the 2/3, 4/5, and L. Those have 3.6-3.8 square feet per passenger, or about 3 passengers per m^2, counting both seated and standing passengers; actual crowding among standees is higher, around 4 passengers per m^2. Using a study of seating and standing capacity (update 2020-2-25: this is a non-link-rotted version of the study), we can get exact figures for average space per standee, assuming all seats are occupied:

Line Peak tph Seats Standee area Passengers Passengers/m^2 1 18 7,920 3,312 13,424 1.66 2/3 Uptown 23 9,200 4,393 28,427 4.38 A/D 17 9,792 3,980 23,246 3.38 B/C 13 6,994 2,899 12,614 1.94 4/5 Uptown 24 8,640 4,752 28,230 4.12 6 21 9,240 3,864 21,033 3.03 F Queens 13 5,967 3,560 17,816 3.33 N/Q/R 23 10,908 6,179 29,005 2.93 E/M 22 8,568 5,856 22,491 2.38 7 24 9,504 5,227 20,895 2.18 L 19 6,080 4,321 23,987 4.14 J/M/Z 19 6,384 4,363 16,657 2.68 F Brooklyn 14 6,426 3,834 14,280 2.05 B/D/N/Q (4 tracks) 38 18,612 10,008 43,550 2.49 A/C 20 10,112 4,504 21,721 2.58 2/3 Brooklyn 16 6,400 3,056 13,536 2.34 R 8 4,608 1,873 5,595 0.53 4/5 Brooklyn 20 7,200 3,960 16,504 2.35

Three additional snags are notable: crowding in 53rd Street Tunnel looks low, but it averages high crowding levels on the E with low crowding levels on the M (see review), and the 1 and 7 achieve peak crowding well outside Midtown (the 1 at 96th at the transfer to the 2/3 and the 7 at Jackson Heights at the transfer to the E/F) whereas the table above only counts crowding entering Manhattan south of 59th Street. But even with these snags in mind, there is a lot of spare capacity on the Upper West Side away from 72nd and Broadway, and in Queens in Long Island City, where passengers can take the undercrowded 7 or M. Crowding in Brooklyn is also low, except on the L. In both Brooklyn and on the West Side locals there’s also track capacity for more trains if they are needed, but New York City Transit doesn’t run more trains since peak crowding levels are well below design guidelines.

This isn’t a small deal. Williamsburg is where there is the most gentrification pressure, but the Upper West Side is hardly a slum – it’s practically a byword for a rich urban neighborhood. The trains serving Brooklyn pass through some tony areas (Park Slope) and gentrified ones (South Brooklyn), as well as more affordable middle-class areas further south. From NYCT’s perspective, developing South Brooklyn and Southern Brooklyn is especially desirable, since these areas are served by trains that run through to Queens, Uptown Manhattan, and the Bronx, and with the exception of the B are all much more crowded at the other end; in effect, lower subway demand in Brooklyn means that NYCT is dragging unused capacity because of how its through-service is set up.

Actual perceived crowding is always higher than the average. The reason is that if there is any variation in crowding, then more passengers see the crowded trains. For example, if half the trains have 120 passengers and half have 40, then the average number of passengers per train is 80 but the average perceived number is 100, since passengers are three times likelier to be on a 120-person train than on a 40-person train.

Subway in New York has high variation in crowding, probably unusually high by international standards, on account of the extensive branching among the lines. The E/M example is instructive: not only are the E trains more crowded than the M trains, but also they come more often, so instead of a perfect E-M alternation through 53rd Street, there are many instances of E-E-M, in which an E train following the M is more crowded than an E train following another E train. I criticized NYCT’s planning guidelines on this account in 2015, and believe it contributes to higher crowding levels on some lettered lines than the table shows. However, the difference cannot be huge. Evidently, in the extreme example of trains with 40 or 120 passengers, the perceived crowding is only 25% higher than the actual average, and even the maximum crowding is only 50% higher. Add 50% to the crowding level of every branching train in Brooklyn and you will still be below the 2/3 and 4/5 in Uptown Manhattan.

So on the Upper West Side and in Long Island City and most of Brooklyn, there is spare capacity. But there’s more: since the report was released, Second Avenue Subway opened, reducing crowding levels on the Upper East Side. Second Avenue Subway itself only has the Q, and could squeeze additional trains per hour by shuffling them around from other parts of the system. In addition, the 4/5 and 6 have reportedly become much more tolerable in the last year, which suggests there is spare capacity not only on the Upper East Side but also in the Bronx.

Moreover, because the local trains on Queens Boulevard aren’t crowded, additional development between Jackson Heights and Queens Plaza wouldn’t crowd the E or F trains, but the underfull M and R trains. This creates a swath of the borough, starting from Long Island City, in which new commuters would not have a reason to use the parts of the system that are near capacity. It’s especially valuable since Long Island City has a lot of new development, which could plausibly spill over to the east as the neighborhood fills; in contrast, new development on the Upper West Side runs into NIMBY problems.

Finally, the residential neighborhoods within the Manhattan core, like the Village, are extremely desirable. They also have active NIMBY groups, fighting tall buildings in the guise of preservation. But nowhere else is it guaranteed that new residential development wouldn’t crowd peak trains: inbound trains from Brooklyn except the 4/5 are at their peak crowding entering Lower Manhattan rather than Midtown, so picking up passengers in between is free, and of course inbound trains from Uptown and Queens drop off most of their peak morning load in Midtown.

It’s not just a handful of city neighborhoods where the infrastructure has room. It’s the most desirable residential parts of Manhattan and Brooklyn, and large swaths of middle-class areas in Brooklyn and parts of Queens. In those areas, the subway is not at capacity or even close to it, and there is room to accommodate new commuters at all hours of day. To the extent there isn’t new development there, the reason is, in one word, NIMBYism.