{"id":6221,"date":"2025-06-14T21:59:46","date_gmt":"2025-06-15T02:59:46","guid":{"rendered":"https:\/\/www.vanshnookenraggen.com\/_index\/?p=6221"},"modified":"2025-08-27T21:41:45","modified_gmt":"2025-08-28T02:41:45","slug":"ibx-north-a-bridge-to-harlem-and-lga","status":"publish","type":"post","link":"https:\/\/www.vanshnookenraggen.com\/_index\/2025\/06\/ibx-north-a-bridge-to-harlem-and-lga\/","title":{"rendered":"IBX North: A Bridge to Harlem and LGA"},"content":{"rendered":"\n

In the previous post<\/a>, I looked at many of the challenges of using the Hell Gate Bridge for the IBX between the Bronx and Queens. Much of the constructive feedback I received asked about a new tunnel instead of using the bridge. Some folks still asked about going to LaGuardia Airport (LGA). Interestingly, no one asked if a new bridge was feasible. In this post, I want to explore why and how the IBX could be extended north, why a new bridge is actually feasible, and where the IBX should ultimately go.<\/p>\n\n\n\n

IBX North<\/p>\n\n\n\n

The current northern terminal of the IBX is Roosevelt Av in Jackson Heights. While this is likely the best possible terminal in terms of multi-modal connectivity (multiple subways and buses serve this station complex), it still leaves out major job centers and connections to other lines to the north. The predecessor to the IBX, the RPA\u2019s Triboro Line, proposed extending service into the Bronx with two branches. The first was along the 149th St corridor, connecting the 6, 2\/5, and 4 trains, along with a proposed new Metro North station at 149th St. The second branch ran up along the Northeast Corridor (NEC) to Co-op City. At first glance, these alignments seemed to be placed along existing (NEC) or former (149th) rail corridors. In actuality, these two branches were designed to serve major areas of employment in the Bronx.<\/p>\n\n\n\n

The 149th St corridor, better known as The Hub, is the historic downtown of the Bronx. Multiple rail, elevated, and subway lines connected riders from all over the borough here. Today, the area is home to a major hospital complex, the Lincoln Medical Center, which makes up 44% of the jobs in the area. In total, there are over 39,000 jobs in a 3\/4th mile radius around 149th St and 3rd Ave, the center of The Hub [Source<\/a>: OnTheMap]. Presently, this area is served by the 2\/5 trains, and both the 4 and 6 trains are about a half mile away.<\/p>

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\"Close\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Close up of the RPA’s 4th Regional Plan transportation map showing two Bronx branches of their Triboro Line.<\/figcaption><\/figure>\n<\/div>\n\n\n

The NEC corridor is home to major hospitals and institutions as well. With over 100,000 jobs in a one-mile radius around the corridor [Source<\/a>: OnTheMap], it\u2019s probably the most important transit corridor *not currently* served by transit (the 5 and 6 trains are both over a half mile away.) This, of course, is changing with the Penn Station Access<\/a> (PSA) project that will upgrade the corridor through the Bronx and add four new Metro North stations.<\/p>\n\n\n\n

Lastly, there is LGA. In 2024, the airport saw over 33.5 million passengers<\/a> pass through the facility. There have been a number of attempts to extend rail transit<\/a> to LGA going as far back as the 1940s, when the airport first opened. Famously, the most recent attempt, an AirTrain from LGA to Willett\u2019s Point, faced community push back and was canceled when it\u2019s biggest champion, Gov. Andrew Cuomo, resigned in disgrace. Advocates had called for the MTA to extend the NYCT Astoria Line (N\/W trains) to the airport instead, but a subsequent Port Authority (PANYNJ) study concluded that, due to issues related to heavy construction near the runway, only improved bus service would be cost-effective.<\/p>\n\n\n\n

As I covered before<\/a>, the Bronx has very good north-south rail transit coverage. What it needs is crosstown, east-west coverage. Theoretically, this dovetails naturally with the IBX, which connects Brooklyn and Queens in a similar crosstown manner. But, while the IBX has a natural path through those two boroughs (along the LIRR Bay Ridge Branch), the proposed Bronx corridors are less simple. <\/p>\n\n\n\n

The 149th St alignment would cross the Bronx at the southernmost effective corridor (that is, the southernmost corridor that connects multiple radial lines.) But as a crosstown service, it requires the majority of Bronx riders to go out of their way to cross the borough; A rider from the northeast Bronx has to travel all the way south before double backing up the west side. If we consider that the most heavily ridden buses in the Bronx are further north, especially along Fordham Rd, the 149th St corridor may not be the best to serve this function.  <\/p>\n\n\n\n

Extending the IBX along the NEC changes the nature of the IBX from a crosstown line to a radial line. The only connection to the existing subway network would be at Hunts Point Av (6), and this would force most riders to transfer. If the IBX is to fill the role of a crosstown line, the line must reach deeper into the borough. Aside from the added cost, this would suddenly render much of the line redundant to existing radial subway lines. It would not serve the boroughs crosstown needs, and be bad at serving its north-south needs as well. The future Metro North service to Penn Station will serve the corridor very well, getting riders to Midtown in about 20 minutes. An additional IBX service would require its own set of tracks, and likely not see as much ridership.<\/p>\n\n\n\n

Northern Nexus<\/p>\n\n\n\n

If using the Hell Gate Bridge is not feasible, and the two logical Bronx alignments don\u2019t hold that much water, where can the IBX go that would best serve the city? Within each outer borough, there is a nexus point where the majority of transit lines meet, then spread out. You\u2019ll find this in downtown Brooklyn at Atlantic and Flatbush Aves, and in Queens at Queens Plaza. It is no surprise that the only existing circumferential transit line, the G train, runs between these two places.<\/p>\n\n\n\n

In Upper Manhattan and the Bronx, the nexus isn\u2019t a point, but a corridor. Almost all of the major trunk lines begin to branch after they cross 125th St (the IRT Broadway-7th Ave Line does branch at 96th St.) While 125th St itself is only tied together by the M60 bus, this is a very popular bus, and the MTA has rightfully eyed the corridor for an extension of the 2nd Ave Subway<\/a>. 125th St is also where Metro North stops before branching.<\/p>\n\n\n

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\"All\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
All railroads lead to Harlem-125th St.<\/figcaption><\/figure>\n<\/div>\n\n\n

The IBX is less about a one-seat-ride and more about connections to other lines; serving Harlem-125th St actually supports it’s main goal. 125th St is the one location where the IBX can go which serves the most riders with the least amount of redundant coverage. Every rail service in the Bronx is accessible (directly or indirectly) from the Metro North Harlem-125th St and Lexington Ave 4\/5\/6 (and eventually Q) complex. This makes Harlem-125th the ideal terminal for a northern extension of the IBX.<\/p>\n\n\n\n

A Harlem extension has other benefits as well. By simple geography, Astoria to Harlem-125th is a shorter distance than 149th St, or anywhere north of there. By tunnel or by bridge, this is cheaper. A Harlem-125th St extension only requires one station, between Park and Lexington Aves, to service most of the Bronx. Should a cross-125th St 2nd Ave Subway extension have been built by the time any of this is actually considered, Upper Manhattan will have access to Queens as well. Alternatively, to get the same coverage in the Bronx, longer tunnels and multiple stations would be required. This is, not surprisingly, the same logic that led the MTA to realign the 2nd Ave Subway across 125th St instead of continuing it to the Bronx.<\/p>\n\n\n\n

The Hell Gate Crossing<\/p>\n\n\n

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\"Randall's\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Randall’s Island nautical chart showing river bottom depths. IBX crossings in red. Source<\/a><\/figcaption><\/figure>\n<\/div>\n\n\n

How do we get the IBX from Jackson Heights to Harlem? When the MTA claimed that the IBX couldn\u2019t fit over the Hell Gate Bridge, and that a new bridge would be needed, most people dismissed the idea outright. In the days of Robert Moses, the city could condemn land for the approach roads. But today, the same level of land taking is seen as too costly, both for the people affected, and for the property values the city would be covering.<\/p>\n\n\n\n

Extending the IBX as a subway might be the most obvious solution. But with NYC transit construction costs being world record breakers, it\u2019s hard to see how a tunnel under the East River would work out. The geology below the Hell Gate Bridge is what helped give the strait its reputation and name. This is the narrowest point in the East River, which is in fact not a river at all but part of the Long Island Sound. Here, strong currents have cut a deep channel under the water. Building an immersed tube tunnel<\/a> (which involves building the tunnel structure offsite and lowering it into the water) would be far too treacherous in these waters. Deep bore tunneling here would need to be especially deep, over 100\u2019, making it very costly.<\/p>\n\n\n\n

Would it be feasible to retrofit the Triborough Bridge to support the IBX? Most likely not. Like all Robert Moses bridges, the spans were never designed for rail transit. There was never a consideration for a second deck, and placing rail on the outer edges of the deck would likely result in uneven loads which would cause the bridge to twist in ways that it was never designed for. This is similar to what happened with the Manhattan Bridge (which was designed for transit), where the trains passing on either side of the bridge put stresses on the bridge that caused it to deteriorate at a faster rate. The Triborough Bridge is a much lighter design, and would likely snap with rails added.<\/p>\n\n\n\n

The Plan<\/p>\n\n\n\n

\"Birds-eye\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Birds-eye view of IBX extension north to Harlem and LGA.<\/figcaption><\/figure>\n\n\n\n

To begin with, we must first locate a location between Queens and Randall\u2019s Island where a new crossing even could be built, with absolute minimal land taking. There is, in fact, one location where a new bridge could be built: between the southern tip of Randall\u2019s Island and Astoria Park South, paralleling the Triborough Bridge. <\/p>\n\n\n\n

This location works for three reasons: the first is that it\u2019s far enough outside the flight paths for LGA<\/a> [PDF] for the necessary height of the bridge. Second, it’s the only location where a subway tunnel (which is required in Astoria to get around the Hell Gate Bridge approach) has enough room to rise from underground to cross over the water. Third, it\u2019s the only location where virtually no buildings would need to be taken to construct the bridge or its approach. If we use this crossing location and work backwards, we can find the perfect solution for a northern extension of the IBX.<\/p>\n\n\n\n

\"Birds-eye\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Birds-eye view of IBX extension north to Harlem and LGA.<\/figcaption><\/figure>\n\n\n\n

Starting at Roosevelt Ave, the IBX will continue along the western side of the Fremont Secondary, crossing over the Brooklyn-Queens Expressway. A new station will be built at Northern Blvd. Continuing north, the IBX will begin to dive into a tunnel portal between 31st and 30th Aves, allowing the IBX to pass under the Fremont Secondary track and eventually the Hell Gate Bridge approach viaduct. From 30th Ave, the IBX tunnel will curve northeast until it reached the BQE West frontage road. The western branch of the BQE has two frontage roads, which the eastern branch lacks. Building a tunnel along these frontage roads will be less complex than trying to build along the eastern branch, which would require building along either a residential street, or St. Michael’s Cemetery.<\/p>\n\n\n\n

The IBX tunnel will run north along the frontage road to 47th St, turning west along Astoria Blvd South to 31st St. There will be stations at Steinway St and 31st St for a transfer to the N\/W trains at Astoria Blvd station. The Astoria Blvd-31st St station will be located under the bridge off-ramp to 31st St and Hoyt Ave South, and will require taking of two small commercial buildings at the corner to allow for vertical egress between the elevated and subway stations. During construction, traffic will have to be rerouted along 29th St and Astoria Blvd. When open, the existing traffic pattern will be restored. Good vertical access will be important here because this station will see high numbers of riders transferring from the subway on their way to and from LGA. The Roosevelt Av station will likely become overcrowded with IBX riders transferring, so the Astoria Blvd station will help ease the load.<\/p>\n\n\n

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\"Overview\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Overview of the proposed 31st Av-Astoria Blvd station complex. Dashed lines are the outline of the lower-level mezzanine, connecting to the vertical access connection with the existing elevated line (blue).<\/figcaption><\/figure>\n<\/div>\n\n\n

Along Hoyt Ave South, on the southern side of the Triborough Bridge, the street consists of a parallel parking lane, bike lane, two moving lanes, a 60-degree parking lane and a shabby sidewalk. By removing the sidewalk and 60-degree parking lane, there is enough room for a 2-track portal and viaduct to be built along the southern edge of the Triborough Bridge. The portal and trackway will be a separate structure from the bridge. This still provides space for a travel lane, bike lane, and parking lane on Hoyt Ave South (or, alternatively, two travel lanes and a protected bike lane.)<\/p>\n\n\n

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\"Cross\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Cross section of Hoyt Av South, present condition and IBX. Streetmix.<\/figcaption><\/figure>\n<\/div>\n\n\n

The viaduct will run along the southern edge of the bridge until 21st St, where it will continue along the southern edge of Astoria Park, allowing for more clearance between the existing and new spans. The new crossing with be a cable-stayed bridge design<\/a>, with one tower just to the west of the Astoria Park Soccer Field, and the other just to the south of Randall\u2019s Island Field #72. The bridge will have space for two tracks. There could also be space for a bike path or walking path, thought vertical access from the Astoria side would need to be worked out.<\/p>\n\n\n\n

Unlike the typical suspension bridges that cross the East River, the new crossing will be a cable-stayed design. Cable-stayed bridges are a favorite of engineers<\/a> for being the most efficient type of span. Unlike traditional suspension bridges, which need huge anchorages on either side of the bridge to anchor the cables supporting the deck, a cable-stayed bridge uses the cables to support the deck on both sides of the main support tower. A benefit of a cable-stayed design here is that more of the existing park space can be saved below the span. The Montreal REM uses the new Samuel-De Champlain Bridge<\/a>, and Sound Transit in Seattle is proposing a cable-stayed bridge for their West Seattle Link extension<\/a>. <\/p>\n\n\n

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\"Birds-eye\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Birds-eye view of IBX extension north to Harlem and LGA. Close up on Randall’s Island with new bridge.

<\/figcaption><\/figure>\n<\/div>\n\n\n

On Randall\u2019s Island, the viaduct would parallel the Triborough Bridge on the eastern side. The line could have a station next to Icahn Stadium, though the utility would need to be studied given its limited use. The line would then turn west, paralleling the Manhattan approach to the Triborough Bridge, descending into a tunnel. The Harlem River runs along the west side of Randall\u2019s Island and is much shallower than the East River. A TBM or an immersed tube could be used to build the short, 600 foot long tunnel under the water.<\/p>\n\n\n\n

In Manhattan, the new tunnel would cut across 124th St from the East River to Park Ave. 125th St would, by this time, contain the 2nd Ave Subway extension. This extension is planned to have a large underground complex connecting to the Lexington Ave Line, as well as an entrance by the Metro North station. The IBX terminal would plug into this complex, providing in-station transfers to the 4,5,6 and Q trains, as well as a connection to Metro North. Given that this station, which already has high ridership, will see even more passengers transferring, a large platform and mezzanine will be required. The tunnel will extend past the station to provide storage space for trains.<\/p>\n\n\n\n

I have not calculated whether or not a new train yard will be needed. This is mostly due to not knowing what is being proposed for the IBX yard planned at Brooklyn Army Terminal. Should additional space be needed, it may be possible to repurpose parking lots under the Triborough Bridge on Randall’s Island for additional tracks.<\/p>\n\n\n

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\"Overview\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Overview of the Harlem-125th St station complex. Running along 124th St, the IBX terminal (pink) will connect with the new Lexington Ave and 2nd Ave lines stations through the to-be-built ancillary buildings (orange).<\/figcaption><\/figure>\n<\/div>\n\n\n

LaGuardia Airport Branch<\/p>\n\n\n

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\"Map\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Map showing how the PANYNJ routed both a NYCT subway and light rail line along an infeasible route.<\/figcaption><\/figure>\n<\/div>\n\n\n

An often proposed northern extension of the IBX is to LGA, directly. Given that the current Q70 SBS bus connects Roosevelt Ave and LGA already, a rail line replacing this route seems to make sense. When Gov. Kathy Hochul killed the previous AirTrain plan, she instructed the PANJNY to consider all other alternatives, including an extension of the IBX (technically, the report proposed a light rail line, but it was noted that this could connect to the IBX.) An extension of the NYCT N\/W trains was also considered. In doing so, the PANYNJ built for themselves a set of parameters so strict that no project other than the cheapest of bus improvements passed the test.<\/p>\n\n\n\n

There is a large interceptor sewer and storm drain that is built virtually around the entire borough of Queens. This sewer collects waste and water from smaller sewers before it reaches the East River and funnels them into water treatment facilities; one of which is located at the edge of Astoria, just west of LGA. This sewer runs along 19th Ave, then roughly along the edge of the airport property, and under the Grand Central Parkway. The route of the NYCT N\/W trains extension, as well as the light rail line, were drawn virtually along the entire route of the sewer tunnel.<\/p>\n\n\n\n

\"Map\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Map of Queens, showing the interceptor sewer (purple line) encircling the borough. Source: Opensewersatlas<\/a><\/figcaption><\/figure>\n\n\n\n

Both the sewer and much of the airport property were built through soggy wetlands, requiring them to be supported underground by hundreds of wooden piles. Wooden piles that are fully submerged don\u2019t rot, so the continued support of both the sewer and airport requires these piles to be undisturbed. Any tunnel would therefore need to be dug especially deep (150-200 feet) to avoid both the sewer and piles. While technically feasible, the high construction cost and extra travel time to reach the surface ruled out this idea.<\/p>\n\n\n

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\"Major\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Major Constructability Challenges for Options Approaching the Airport from the West and Southwest. PANYNJ<\/figcaption><\/figure>\n<\/div>\n\n\n

FAA restrictions prevent construction and even temporary tall structures within a certain distance from runways. This eliminates any type of viaduct would run too close to the runway. Even using cranes for tunnel construction is out. When considering extending either the NYC subway N\/W trains from Ditmars Blvd or an extension of the IBX from Roosevelt Ave, the PANYNJ consultants routed both options directly through the restricted zone. <\/p>\n\n\n\n

If we imagine that the PANYNJ never wanted to build the AirTrain in the first place (this was one of Andrew Cuomo’s bright ideas), it\u2019s easy to see why they set up an unworkable plan from the beginning.<\/p>\n\n\n\n

In order to find a solution that could actually work, while considering the real physical constraints, we can find an alternative route which combines the best of the NYCT N\/W trains and IBX extension. <\/p>\n\n\n\n

In the plan I outlined above, the IBX tunnel would hug the BQE frontage road before turning west along Astoria Blvd. Where the line turns, a branch can be constructed that would turn east, along the Grand Central Parkway. This branch would connect to both the southern leg (to Brooklyn) and western leg (to Harlem) via a flying junction, accomplished by constructing a bi-level tunnel.<\/p>\n\n\n\n

The branch would continue east in a tunnel under Astoria Blvd South to 82nd St. Instead of hugging airport property, the new tunnel runs around it: at 82nd St the tunnel makes a slight turn down 24th Ave until 88th St. There would be a station at 82nd St for local riders, and for a short shuttle bus connection to LGA Terminal A, with an intermediate station at Hazen St.<\/p>\n\n\n\n

The city block bounded by 88th St, 23rd Ave, 89th St, and 24th Ave contains a giant parking lot for Budget Car. This is where a portal will be built. The line will make a sharp turn north at 88th St, come above ground, and cross over the parking lot of Vaughn College on a viaduct. The line then crosses over the Grand Central Parkway, outside the restricted zone, and continues to both LGA terminals. Stations will be at Terminal B, and Terminal C.<\/p>\n\n\n

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\"Map\n\t\t\t\n\t\t\t\t\n\t\t\t<\/svg>\n\t\t<\/button>
Map showing how the IBX North alignment avoids the LGA runway and interceptor sewer issues.<\/figcaption><\/figure>\n<\/div>\n\n\n

The IBX will shift from a simple line connecting Brooklyn and Queens into a complex network linking Upper Manhattan, the Bronx, Westchester Co., and LGA as well. Three services will be established: the X train from Brooklyn Army Terminal to Harlem-125th, the Y train from Brooklyn Army Terminal to LGA, and the Z train from Harlem-125th to LGA. (The existing Z train, which runs skip-stop service with the J can simply be renamed the K or something else.)<\/p>\n\n\n\n

The IBX as it\u2019s proposed today is 14.5 miles long, built along an existing ROW, with 19 stations, is said to cost $5.5 billion. Now, this number was calculated before the tunnel under All Faiths Cemetery was added (not to mention the new Trump tariffs.) My assumption is that a more realistic cost-estimate is around $7 billion, which is still a good value for what the IBX will bring.<\/p>\n\n\n\n