If you take the J, M, or Z trains from Marcy Avenue, be prepared to meet a few thousand new friends starting next year. Victor J. Blue/Bloomberg via Getty Images

During the upcoming L train shutdown set to begin in early 2019, the MTA expects 70 to 80 percent of displaced L riders to take other subway lines. This will affect not only those displaced riders but all the commuters who currently take the lines that will become filled with L refugees. This week, the Village Voice examines the impact on the J/Z lines, as well as the Brooklyn end of the M.

The J/M/Z lines never stood a chance. Geographically speaking, they’re the only subway lines that roughly approximate the L’s journey through north Brooklyn. They’re also the only Manhattan-bound tracks within walking distance of the L, especially in the areas most impacted by the shutdown. As a result, it’s no surprise the MTA and DOT expect the J, M, and Z to pick up the largest share of riders for the fifteen-month period the L is scheduled to be out of commission.

The MTA hasn’t released any official ridership estimates for the shutdown, but we can do some back-of-the-envelope calculations using this very rough guide the MTA released back in June.

If 75 percent of the 225,000 L train riders who currently cross the East River every weekday continue to take the subway, and roughly half of those displaced riders switch to the J/M/Z, that’s about 85,000 additional riders every day. And even if it’s a mere tens of thousands of extra riders a day, this will be a very big problem.

There are two big worries about the capacity of the J/M/Z lines: Will there be enough trains to transport all these passengers? And will there be enough platform space to hold all the waiting riders?

The two questions are related: The more trains the MTA can run, the fewer passengers will be left waiting on the platform. But they’re not identical, since even with a train every few minutes, the platforms will still need to be wide enough to handle all those people.

Unfortunately, it’s hard to picture the MTA being able to run enough J/M/Z trains to deal with the expected shutdown crowds. During the morning rush hour, the L currently runs about 20 trains per hour through Bedford Avenue. Marcy Avenue, the last stop on the J/M/Z before crossing the Williamsburg Bridge, currently sees about 16 trains per hour at peak periods. The MTA hasn’t provided specifics about how many additional J and M trains it plans on running, but even if it’s several more per hour through Marcy, each train can fit only about 1,200 people. The math simply doesn’t add up.

But station capacity is arguably the bigger concern. This is what Marcy Avenue looks like during a normal weekday rush hour:

Only @MTA and @NYC_DOT could see something like this and think “yeah we can fit an extra 10-20k people here” pic.twitter.com/ICCTnOUcRx — Philip Leff (@philipleff) December 18, 2017

None of the MTA’s planned mitigation efforts are designed to increase platform capacity. In 1999, when the Williamsburg Bridge was shut down for five months to repair signals and tracks, the middle express track at Marcy was converted into a temporary platform. In theory, the MTA could do this again — the express track will be out of use west of Myrtle-Broadway during the shutdown — so long as it added some kind of staircase and overpass to allow passengers to access the new platform. Perhaps there are logistical reasons why this can’t be done, but the MTA has never mentioned even exploring this option and didn’t respond to Voice queries about the possibility.

In short, it’s unclear where all these extra riders will stand while waiting for trains, or how anyone will disembark at these overcrowded stations. It’s easy to imagine a scenario where MTA employees have to be deployed outside of stations to manage crowds and ensure the platforms don’t become dangerous. It’s also easy to imagine this not being done until after something bad happens.

I’m especially worried about what will happen at the first four stops in Brooklyn: Marcy, Hewes, Lorimer, and Flushing, which are all small, two-platform stations with few entrances and exits. Lorimer and Marcy are slated to get more turnstiles, and Marcy will get wider stairs as well, but none of this will actually help once commuters get onto the crowded platforms.

Meanwhile, the new free transfer the MTA plans to put into place between the Broadway G station and Lorimer and Hewes will only encourage even more displaced L riders to use those two stations. A free transfer is generally a good thing, but I’m deeply concerned about how many passengers those stations can realistically accommodate. They are two of only a handful of stations within walking distance of an L stop that have direct Manhattan access, so they will receive a lot of increased foot traffic. The Montrose L station (7,000 daily weekday swipes into the station, according to 2016 ridership stats, the most recent year available) is a 10 to 15 minute walk from the J/M/Z Lorimer stop (5,000 swipes), and some people who currently walk to the Morgan Avenue (7,500 swipes) or Grand Street L (7,000 swipes) will likely walk the 20 to 25 minutes to Lorimer or Flushing (9,300 swipes). Where are all these people supposed to go?

A similar conundrum faces the M spur at Central, Knickerbocker, and Myrtle-Wyckoff avenues, since all of those stations are within fairly short walking distances of the L. (Myrtle-Wyckoff has a direct connection with the L.) Those stations have similar layouts to the Hewes-Lorimer-Flushing stops, so it’s unclear what kind of increased capacity they can support. Even worse, those three M stops only get, well, M trains, not J/Z as well, so there will be fewer trains to deal with all these people.

What You Should Do If You Currently Take the J/M/Z

I really hope you didn’t expect me to reveal some kind of secret transit system, because I don’t have one for you. Here is what I will advise, ranked by likelihood of avoiding fifteen months of commuting nightmares:

Move far away from north Brooklyn. Bike to work. I highly recommend you start soon so you can get accustomed to it, because even the bike lanes will become overcrowded during the shutdown. It sounds like the city will soon legalize pedal assist e-bikes — e-bikes are pretty awesome — which should bring bike commuting within reach of more New Yorkers. If you absolutely don’t want to (or physically can’t) bike all the way into Manhattan, consider getting a cheap bike, riding to downtown Brooklyn, locking up your bike outside a subway station, and heading into Manhattan from there. If you have a flexible job, adjust your schedule to commute during off-peak hours. And by off-peak, I don’t mean 10 a.m. to 7 p.m. I mean, like, 11:30 a.m. to 8 p.m.

I understand these are fairly privileged recommendations. Not everyone can afford to move, not everyone can ride bikes, and not everyone can change the hours they go to work. But it’s the best I can do. We’re all just very, very screwed.