How Would the Interborough Express Serve New York City?

How Would the Interborough Express Serve New York City?

An analysis shows the impact the proposed rail service could have on mobility and land use.

By Eric Goldwyn
and Elif Ensari

New York Governor Kathy Hochul kicked off 2022 promoting the Interborough Express (IBX), a new transit project connecting Brooklyn and Queens in New York City. While the project is in its earliest stages, the broad outline is to reintroduce passenger transit service along an existing railway that’s currently used for freight.

MTA has identified a number of critical needs that the project would address, including improving transit service in parts of Brooklyn and Queens, supporting economic development by promoting transit-oriented development, and improving transit access to employment centers.

It’s estimated that the proposed service would reach nearly 100,000 riders per day along the 14-mile alignment. While there’s a long way to go before IBX enters into service, an analysis of travel behavior and land use along this corridor shows how it could have a transformative effect on neighborhoods in Brooklyn and Queens, and on New York City overall.

Some findings we explore below (click links to jump ahead):

  • Connecting travelers: Pre-pandemic, there were about 12,000 subway trips daily that started and ended in the IBX corridor — a small but meaningful number given limited connectivity.
  • Mode share: Transit mode share within the corridor is low, but considerably higher for trips ending in it.
  • Land use: Existing land-use data shows strong potential for transit-oriented development in the area.

How IBX would connect Brooklyn and Queens

Subway lines crossing the Interborough Express route.
Data sources: 1. Interborough Express alignment: Ben Oldenburg 2. Subway lines: OSM

According to Replica Places’ 2019 data, a typical weekday saw approximately 12,000 subway trips that started within a half-mile of the IBX route, went into Manhattan, and then returned to somewhere in the corridor. That makes up less than 2% of the total trips that start and end within the current IBX corridor, but they are significant, in our view, because they capture how poorly the current subway network facilitates these trips.

By stitching together several subway lines at their outer reaches, IBX could facilitate these kinds of trips that currently require lengthier journeys toward or into Manhattan. All of these circuitous trips, which averaged 43 minutes each way, required subway-to-subway transfers, at a minimum.

IBX could also support greater transit equity for the city: Black and Hispanic commuters are overrepresented in these long journeys, comprising 62.7% of long subway trips within the corridor, compared with 50.4% of all trips within the corridor.

Charts of race and ethnicity breakdowns of travelers within the IBX corridor. The population of subway trip-takers is 37.2% Black, 25.5% Hispanic or Latino, 22.2% white, and 13.2% Asian. The population of all trip takers is 29.4% white, 27.1% Black, 23.3% Hispanic or Latino, 18% Asian.
Source: Replica

IBX would dramatically simplify this trip by eliminating the subway-to-subway transfer and detour through Manhattan. Faster, more predictable trips via IBX should also stimulate ridership and attract more riders who currently opt for driving, or choose not to make similar trips altogether.

Replica Places shows attributes of long subway trips that start and end within the IBX corridor.

In addition to the benefits of creating new single-seat rides within the corridor, IBX will likely be used by passengers to transfer to another line within the corridor rather than serve complete trips. Over time, however, we imagine that it will also spur new kinds of development within the corridor, which will encourage more single-seat rides within it.

Today’s subway ridership supports the case for IBX

Of the 640,000 trips per day across the IBX corridor, more than 25% are made by automobile, compared with only 10% that are made by bus or subway.

But trips that originate outside the IBX corridor and terminate inside of it look notably different. Of the nearly 400,000 daily trips into the IBX corridor, 58% were made by public transit. This sharp contrast suggests that when New Yorkers can find a bus or subway to take them to their destination in the IBX corridor, more often than not, they will opt for transit.

This is an encouraging finding: It suggests that better connectivity throughout the corridor will lead to greater transit ridership within it.

Percentage of total trips made by transit terminating in the IBX alignment.
Data sources: 1. Travel data: Replica; 2. Interborough Express alignment: Ben Oldenburg; 3. Subway lines: OSM.)
Trips within IBX bufferTrips into IBX buffer
Total trips640,000380,000
Public Transit9.8%58%
Private Auto13%13.6%
Taxi0.7%1.0%
Auto Passenger13%0.5%
Biking8.1%0.5%
Walking48.6%20.4%
Commercial/Freight2.2%6%

What IBX means for land use and transit-oriented development

Another exciting element of IBX is its potential to give low-density areas of the city a chance to redevelop around transit infrastructure, rather than dedicating more space to asphalt.

When we looked at the distribution of land uses within a half-mile of the alignment, we found that IBX will run through neighborhoods where the largest share of the zoning permitted low-density housing. According to Replica’s land-use data, the leading land use in the study area is single-family residential, which accounts for 36% of the land area.

Source: Replica

The second largest land-use category in the study area is multi-family residential, but it only accounted for 19% of the land area. By increasing the amount of density allowed along the corridor, there will be greater opportunities to create vibrant mixed-use neighborhoods similar to those found closer to the center of the city, develop more housing, shift driving trips, and absorb additional population as it moves to Brooklyn and Queens.

These supportive land-use changes are especially critical where IBX intersects with other trains, such as in Midwood, Brooklyn or Middle Village, Queens where IBX will connect with the M train. Middle Village, even on its busiest streets, such as Fresh Pond Road is dominated by two- to four-story buildings and suburban style strip malls. On side streets, like Admiral Avenue, the zoning is more restrictive, with height caps that limit buildings to a maximum of 35 feet even though Admiral Avenue is adjacent to the Metro Mall and the M train’s terminus.

Land use around the IBX corridor.
Data sources: 1. Land use: Replica; 2. Interborough Express alignment: Ben Oldenburg; 3. Subway lines: OSM.

One of the six project goals for IBX is to promote transit-oriented development and stimulate investment along the corridor. The best way to maximize the potential of transit-oriented development is to allow a bit more density along the corridor. By allowing bigger buildings and eliminating parking requirements, IBX can be a catalyst to transform single-family properties into six- to ten-story multifamily apartment buildings whose residents will use IBX, drive ridership, and justify the final cost of building IBX.

Even if the existing zoning along the corridor doesn’t change, we anticipate that IBX will allow demand for housing to spread more evenly across the corridor so that people can find housing adjacent to transit more easily. Just as we expect more people to use IBX to travel within the corridor via transit than currently do once IBX opens, we believe that IBX will make it more attractive to live within the IBX corridor in areas that aren’t well served by the subway, such as portions of East Flatbush and Maspeth, and by promoting new development at nodes like Broadway Junction, which will now see IBX intersect with the J, Z, A, C, L, and Long Island Rail Road.

In the last decade, according to our analysis, which differs from the MTA’s, we found that the population within the corridor grew by 7% from 600,700 to 642,821. Similarly, Brooklyn and Queens saw their combined populations increase by nearly 9% or 400,000 residents between 2010 and 2020.

More transit infrastructure and more housing are needed to keep pace with this robust population growth. As the areas around existing subways, such as the lines that extend beyond the proposed IBX alignment without intersecting, such as the 2, 3, 4, 5, F, B, Q, D, and R, become more expensive and crowded, IBX will enable that pent up demand for housing to locate anywhere within the corridor because there will be no gaps in the subway network, which enable access to New York’s schools, jobs, and amenities.

IBX has the potential to improve New York’s transit network by strengthening connectivity across the network and bringing denser, transit-oriented development to low-density areas of the city. Density, when combined with ample housing, jobs, and ubiquitous transit, provides the framework for a more sustainable, productive, vibrant, and equitable city.

Eric Goldwyn is a program director at NYU’s Marron Institute of Urban Management.

Elif Ensari is a research scholar at NYU’s Marron Institute of Urban Management.

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