It’s T-minus three days and counting until the MTA begins its long-planned repair of the Canarsie Tunnel, disrupting the lives of the roughly 225,000 commuters who use the L train on a daily basis.

L riders who spent the past few years bracing themselves for a full cessation of service between Brooklyn and Manhattan now have a new set of challenges to contend with. The plan that will be carried out, cooked up by a panel of engineers hired by Gov. Andrew Cuomo at the end of 2018, will not require the Canarsie Tunnel to be closed entirely. Instead, work can be done on one track at a time, meaning trains can still run during rush hour and at off-peak hours.

But even though the new method of repairing the tunnel won’t necessitate a full shutdown—a fact that many praised when it was announced in January—that doesn’t mean service on the L will be pleasant during the 15 to 20 months (a specific timetable has yet to be determined, per the MTA) repairs will be taking place. Many transit advocates believe there’s a chance things will be just as bad—or worse—than they would have been during a full L train shutdown.

“We’re less prepared now for this plan, that would seem to be less of a disruption, than we would have been for the full 15 month shutdown,” says Joe Cutrufo, the communications director for Transportation Alternatives. “There was a really good mitigation plan for that. The mitigation plan for this partial shutdown is nowhere near as good.”

To recap, on weekdays, L trains will run as usual during rush hour, but will have limited service at night. Starting at 8 p.m., service will start to slow down so work trains can move into position, and subways will run every 20 minutes—that’s three L trains per hour—between 10 p.m. and 5 a.m. On weekends, that three-L-trains-per-hour schedule will be the norm. And as anyone whose ridden the L train on a weekend knows, trains can get crowded even outside of the rush hour commute.

“The problem is the weekend peak hour, our ridership is 8,000 riders per hour,” explains Danny Pearlstein, the policy and communications director of Riders Alliance. “And with trains running every 20 minutes, the maximum that can be accommodated is 4,800 an hour. So that’s 3,200 frustrated riders in a weekend peak hour every weekend for who knows how long.”

The MTA has advised riders to anticipate crowding at subway stations in Manhattan and Brooklyn, most recently in a series of tweets about service options during the slowdown:

L trains will run every 10 minutes in Brooklyn between Rockaway Pkwy and Lorimer St. Every other L train will continue into Manhattan. In Manhattan and at Bedford Av, the L will arrive every ~20 minutes, but at certain times, it may be too crowded to board the first train. (2/8) pic.twitter.com/kStqMmctof — NYCT Subway (@NYCTSubway) April 22, 2019

There are also plenty of alternative service options—more 7, G, and M trains, free transfers between stations, and special “Williamsburg Link” buses to shuttle riders to and from stations in that neighborhood. But whether or not riders use those, or decide to try and take their chances with the L, remains to be seen.

“I think before with the shutdown plan, that was going to be tough, too, but people had pretty clear choices about what the most direct route was going to be,” says Ben Fried, communications director at TransitCenter. “And with this plan, it’s less clear. I expect there to be really intense crowding at the stations on either side of the river.”

If crowding becomes an issue, the MTA has not ruled out making some high-traffic stations, like First and Third avenues, exit-only to deal with overflow. But that could lead to additional problems: overcrowding on platforms; riders clamoring to get onto buses; frustrated commuters; and ultimately, more riders turning to other options, like ride-hailing apps, to get from place to place (which will, in turn, lead to more congestion on city streets).

“What we’re looking at without an excellent public transit option above ground that’s direct, fast, [and] reliable, we’re looking at a mini L-pocalypse or L-mageddon on a weekly basis, if not more frequently,” says Pearlstein.

Buses could serve that need for direct, fast, and reliable service through Manhattan, but as of this writing, it’s unclear how they will fit into the larger spate of transit options during L repairs. One of the biggest issues cited by the advocates Curbed spoke with is the lack of clarity around the city’s plan for buses along 14th Street. Originally, when a full shutdown was planned, the MTA and the New York City Department of Transportation floated the idea of a dedicated busway on 14th Street between Ninth and Third avenues. This would have allowed the various M14 routes (A and D) to move seamlessly along the thoroughfare, without interruption from private cars or other vehicles.

We’re looking at a mini L-pocalypse or L-mageddon on a weekly basis, if not more frequently.

“This is official city policy, to be speeding up buses 25 percent and to reduce carbon emissions, and all that stuff justifies going ahead with the full busway,” notes Fried. “We’re talking about one of the most intensely-used surface transit routes in the city, if not the most intensely, even before a shutdown of the L train.”

But it’s unclear if a busway will actually end up happening; the city and the MTA have promised that they’ll release bus plans sometime this week, and the clock is ticking. Plans are in the works to add a SBS line on 14th Street this summer, but even that won’t do much to get people moving faster—on average, SBS lines move only slightly faster than local bus routes, according to an analysis by Comptroller Scott Stringer’s office.

“There could have been a way to do this where I would be telling you right now, the DOT and the mayor, they forged ahead and they decided that better bus service was a priority even without the full shutdown,” says Cutrufo. “I could be telling you that now, but I’m not, because they’ve been really kind of weak on making the 14th Street bus corridor work better. The fact that just regular old select bus service is coming, I don’t see it being a dramatic improvement.”

So what advice do these advocates have for riders who may soon find themselves in dire commuting straits? “I would say now’s a good time to get comfortable biking on New York City streets if you’re capable and courageous,” Cutrufo says. (May is Bike Month in NYC, after all.) Even without pedal-assist Citi Bikes on the roads—they were recently removed due to safety concerns—biking is still fast and relatively attractive for those who are able to do so.

Fried, meanwhile, suggests commuters “get loud and agitate” if it becomes clear very quickly that the slowdown is turning into an L-pocalypse. “If things don’t work out the way we’re expecting with the substitute service, it’s not too late to implement a better plan,” he says. “These are inherently flexible modes that can be set up at relatively short notice. We’ve had very high-capacity, temporary bus lines set up to deal with natural disasters and after 9/11. The city and the MTA can mobilize quickly if things don’t work the way they’re supposed to.”