Why the 125th Street Subway Is a “Now or Never” Project for New York City
In her 2026 State of the State address, Governor Kathy Hochul announced plans to extend the Q train across 125th Street, potentially creating Manhattan’s first new crosstown subway in generations.
It’s ambitious and expensive. But I think the MTA has done their homework. I read through the entire feasibility study so you don’t have to.
For about $7.7 billion dollars, it will add 3 more stations to the Q to create transfers at the existing subways along 125th St.
Why are we even talking about this if it’s at least a decade away?
The Key Logic Behind the 125th Crosstown Subway: Keep The Tunneling Machines Moving to Save Time + Money
There are many reasons why building new subways is crazy expensive in a city like New York. Two of them are…
- The tunnels
- The delays
If we prioritize the 125th St subway, the tunnel machines can keep going while they’re building the Second Avenue extension to 125th st.
If you keep the construction going while everyone’s already on-site, it saves years of time and serious costs.
Right now, the MTA is building Phase 2 of the Second Avenue Subway, which will extend the Q train from 96th Street up to 125th Street and Second Avenue.To build those tunnels, the MTA is using two massive TBMs that will bore their way north under Second Avenue.
Those machines are a challenge to remove or dispose of. And the MTA has three options:
- Bury them in place (yes, this is actually common. There are abandoned TBMs under cities all over the world)
- Dismantle them and haul them out piece by piece (expensive and time-consuming)
- Keep them going and tunnel west under 125th Street
The Window for This is While We Build The Second Avenue Subway
We’re talking about this now because to keep the tunneling going, we need to start planning it now.
Instead of treating the 125th Street extension as a separate project that would require buying new TBMs, setting up new staging areas, and starting from scratch years from now, they’d just keep the existing machines running.
The MTA’s feasibility study makes this urgency crystal clear: “If the SAS Phase 2 tunnel construction contract proceeds as currently defined, without close coordination of design between the two projects, it will be difficult to tunnel west in the future. There is a window of opportunity now to preserve the option for a future 125th Street Subway.”
Translation: It’s now or probably never.
Project Details: Three Stations, Three Scenarios
The MTA studied three different buildout scenarios for the 125th Street Subway, and the ridership numbers tell a compelling story about network effects.
Scenario 1: One station at Lenox Avenue. About 57,300 daily riders, including 500 new transit users who weren’t riding the subway before.
Scenario 2: Two stations—Lenox Avenue and St. Nicholas Avenue. About 115,900 daily riders, with 2,700 new transit users.
Scenario 3: Full buildout with three stations—Lenox Avenue, St. Nicholas Avenue, and Broadway. About 163,900 daily riders, with 5,500 new transit users.
Each additional station more than doubles the number of new riders. That’s the magic of network effects in transit. When you connect more neighborhoods to more subway lines, the value of the entire system increases exponentially, not linearly. The full three-station buildout makes the most sense precisely because of these network effects.
Three stations give you a true crosstown line that changes how people can move through upper Manhattan and access the Bronx.
The total estimated cost for the full three-station buildout is $7.7 billion (in 2027 dollars).
That’s an enormous amount of money. But, it provides connections to the 2, 3, A, B, C, and D, trains, in addition to the 4, 5, 6.
Which Tunneling Option is Best? [Explained for Non-Engineers]
Alright, this is where things get technical, but I promise to keep it digestible. I’m not an engineer, so I had to wrap my head around this too.
To build this subway, you need tunnels. And to build tunnels, you need those tunnel boring machines (TBMs) I mentioned earlier.
The question is: where do you start the machines, which direction do they go, how many do you use, and where do they end up? You can have them go East to West, you can drop them in the middle and go out both directions.
The MTA studied five different tunneling options. Only two options don’t delay the start of service on Phase 2 of the Second Avenue Subway.
This, in my opinion, is absolutely crucial.
You cannot afford to push back the Second Avenue Subway, which people have been waiting on for literal generations. That’s how you kill support for further expansions.
The Option That Doesn’t Delay and Keeps The Tunnel Machines Moving
This is the elegant solution.
When the two TBMs finish boring north under Second Avenue to 125th Street, instead of stopping, they’d be redirected to tunnel west under 125th Street. The MTA would set up a new staging site near something called “Ancillary A” (basically a construction access point near Second Avenue and 125th Street), which keeps the 125th Street tunneling work separate from the ongoing Second Avenue construction.
I learned from reading that the site where the machines go in (the insertion site) requires way more space and activity than where it ends (the extraction site). If you coordinate with the Second Avenue Subway, then you don’t need a separate TMB insertion site at all.
The TBMs would bore all the way to 12th Avenue on the west side, where they’d either be removed or buried. This option takes advantage of momentum.
The other option that doesn’t delay the Second Avenue Subway is starting from the west side. The advantage here is that it can be done completely independent of the Second Avenue Subway Phase 2 construction. The disadvantage is that you need to deal with burying the Second Avenue Subway TBMs separately, which adds technical challenges.
Tunnel-Only Phase For $1.1 Billion: “Phased Implementation”
In the study, the MTA mentions the option of doing a “phased implementation.” This is where they focus on building the tunnels first for $1.1 billion.
You build the tunnels while the Second Avenue Subway construction is happening and the equipment is all there. Then you finish the stations, tracks, signals, and electrical systems later when more funding becomes available.
The study puts it plainly: “It would be difficult to advance the full-build Project in time to take advantage of the SAS Phase 2 construction momentum and mobilization activities that could save time and money for 125th Street Subway in the long term. There is, however, an opportunity to advance the Project incrementally, syncing just the tunnel portion of 125th Street Subway to the tunnel construction for SAS Phase 2.”
This is the move.
125th Street Subway vs Bus Rapid Transit
I read a lot of comments sections, and people brought up some decent points. One of them was that 125th St really needs bus rapid transit, and can have that for like, 1/200 of the cost, and could be done by next year.
125th Street could be redesigned with better dedicated bus lanes and limitations on private cars like 14th Street within a year, for a fraction of the subway’s cost. And it absolutely should be.
It would speed up over a dozen bus routes. Can’t that do the same thing as a subway? Well, sort of.
In my opinion, both of these should happen.
A busway on 125th Street would provide immediate relief. It would move thousands more people more efficiently than the current congested mixed-traffic situation.
But a subway provides a lot more capacity and ease of transfers. Think about a subway train with 8-10 cars attached vs a bus that fits 40 people. Subways can handle dramatically higher ridership. It provides people from various train lines a one-transfer ride to the Upper East Side. That could be someone coming from an A train in Upper Manhattan, or a D train in the Bronx, in addition to all the people along 125th who now get one-seat east side access.
They feed into each other
More importantly, these investments feed into each other. Transit-rich environments benefit from a positive feedback loop. Better transit attracts more transit riders, which creates support for even better transit, which attracts more investment. The 14th Street busway made 14th Street better for everyone. A 125th Street busway would do the same. And a 125th Street subway would multiply those benefits even further.
After all, lots of people take the L train on 14th St and ride the M14 buses.
We need the busway in 2027. We need the subway by the mid-2030s. These aren’t competing priorities.
What About [Insert Other Transit Project Here]
After Hochul’s announcement, I saw a flood of comments: “What about QueensLink!” “The Bronx is still waiting for a crosstown subway!” “Second Avenue Subway Phase 3 is more important!”
I get it. Transit budgets are limited, and we have to make choices.
But let’s talk about what the 125th Street Subway actually does for the outer boroughs, because I think this gets overlooked in the “Manhattan gets everything” discourse.
The 125th St Subway Helps Bronx Commuters
The 125th Street Subway gives every single subway line in the Bronx a connection to the Q train. If you’re coming from the Bronx on the 2, 3, 4, 5, 6, B, or D, you can transfer at 125th Street to reach the Second Avenue corridor, and onward to where the Q goes, including Times Square and South Brooklyn.
Possible Interborough Express Connection
And here’s where it gets really interesting for outer borough connectivity. If the Interborough Express (IBX) extends to Harlem-125th as Andrew Lynch and others have proposed, the 125th Street Subway becomes even more valuable.
Think about the network effects: Bronx riders could take their local train to 125th Street, transfer to the Q heading into Brooklyn, or maybe transfer to the IBX to reach Queens. That’s new connections between the Bronx and Queens, new options to Brooklyn, all converging at one crosstown corridor.
The MTA’s feasibility study doesn’t discuss these IBX connections because the IBX itself is still being planned, but the potential is there. This is the kind of multi-generational infrastructure planning that could reshape outer borough transit in ways we’re only beginning to understand. (I wrote more about whether the IBX could reach the Bronx in this article if you’re interested.)
So while I understand the frustration that Manhattan is getting another subway line, the 125th Street extension benefits more than Manhattan.
About Second Avenue Subway Phase 3
Yes, Phase 3 (from 72nd Street down to Houston Street) would serve more people and might have a stronger case based on pure ridership numbers. And yes, advancing the 125th Street extension might push Phase 3 further into the future.
But Phase 3 doesn’t have the same “now or never” timing issue. The 125th Street extension has a window of opportunity because of the Phase 2 construction. If we don’t build it now as a continuation of Phase 2, we’ll have to start from scratch later at much higher cost.
The ideal answer, obviously, is to do everything: QueensLink, IBX, Second Avenue Subway Phase 3, the 125th Street extension, better Bronx transit, all of it. But if we’re being pragmatic about sequencing, the 125th Street extension makes sense now.
Concerns About Gentrification
This comes up with every transit expansion or street improvement, and it’s a real concern that deserves to be taken seriously.
Better transit does make neighborhoods more desirable. People want to live near good subway connections. That increased demand can drive up rents and property values, potentially displacing longtime residents.
I don’t love this argument because the end logic of avoiding transit improvements to prevent gentrification is that poor neighborhoods should have worse infrastructure.
Making things better attracts people. That’s unavoidable. The way through this isn’t to avoid improvements, it’s to ensure that the people who’ve lived in these neighborhoods for generations can stay and benefit from those improvements too. And that’s a different discussion. (I have taken a whack at real ideas to prevent gentrification here.)
The real issue isn’t whether we should improve transit. It’s whether we protect and support the people already living there when we do. That means strong tenant protections, affordable housing requirements, anti-displacement policies, and community investment that benefits existing residents rather than just attracting new ones.
(I’ve written more about this in my article on gentrification and transit, if you want to dig deeper into the policy solutions that can help.)
A Realistic Transit Dream Map For My Kids
I don’t have kids, so I hope that by the time I do and they’re old enough to take the subway by themselves, they’ll have a pretty sweet service map:
- Second Avenue Subway Phase 2 (service starts 2032, so this should definitely be running)
- 125th Street Subway (if we do the phased approach and get the tunnels built soon)
- QueensLink
- Interborough Express (the orbital line connecting Brooklyn and Queens)
- Bonus: IBX extension to 125th Street (connecting all those outer borough lines)
Is this realistic? Maybe. Maybe not all of it. But if we fight for it, if we make the right choices now, maybe we will.
