Density, Landuse and Travel Statistics for NYC Subway and Proposed IBX Station Areas
Data presented in the below charts have been retrieved from multiple sources, and aggregated per buffer area that are shown in the following map.
https://transitcosts.com/NYU/IBX/MAPS/Station_Areas/index.html#13
The buffer areas have been determined based on the boundaries of census tracts that overlap with a 800-meter (0.5 mile) radius circle around every NYC subway station and proposed IBX station locations.
Each pair of box and whiskers in these charts represent the range of values found for all the existing subway station buffer areas (on the left) and for the station buffer areas around the proposed IBX stations (on the right). The station areas with outlier values are represented by blue circles, and values within the 2nd and the 3rd quartiles are shown by the colored boxes. Whiskers represent the 1st and the 4th quartiles. Hover over the chart to see more detail. (Outliers are calculated by x> Q3 + 1.5*IQR and x<Q1 – 1.5*IQR, where x=the outlier values, Q1 and Q3= the upper values of the first and the third quartiles, and IQR=Q3-Q1).
Density Stats of All Stations
Density Stats of All Stations Excluding Manhattan
Here we look at the most commonly used indicators as part of Transit Oriented Development assessments.
Population density per square mile
(Data source: Replica)
Analyzing 4,399 stations in 2010 3,417 stations in 2000 (existing and proposed fixed transit) in 54 metropolitan areas in the US, Renne and Ewing found that where the density is 25,000 residents/square mile or higher, 40% of the commuters traveled on public transit, where it is between 10,000-25,000 residents/square mile, share of transit commuters dropped to 14% and between 4,000-10,000 residents/square mile, only 2% of the commuting trips happened on transit.
The median density across all station areas excluding the IBX stations is 46.5k/sqm, for station areas excluding the Manhattan and IBX stations, it is 43.6k/sqm and for the IBX stations, it is 39.2k/sqm. While the IBX stations are less dense than the other station areas, a majority of them fall in the range that according to Renne and Ewing, would be considered TOD areas. The most densely populated IBX station area is the northern terminus Roosevelt Avenue where the IBX is planned to connect with the E,F,M,R and 7 trains; while the least dense area is the Metropolitan Station area it is to connect with the M line.
Built Area per Acre
(Source: Map Pluto)
Total built floor area (in square feet) per acre of land is considered an important metric representing density of the built area, independent from the kind of use or the buildings occupancy.
Residential Units per Acre
(Source: Map Pluto)
The number of residential units per acre of land, is another commonly used metric that determines the “TODness” of station areas, as the more residential units there are, the more number of trips a transit station is expected to generate.
A wide range of values for this metric has been considered “the minimum” for a station area to be considered a successful TOD, by researchers. Cervero and Guerra take 9 and 12 households (hh) per acre as minimums for light rail and heavy rail transit respectively. Renne and Ewing found that across the US fixed transit stations that they consider TOD, 78% have more than 8 residential units/acre, and only 29% TODs have more than 25 residential units/acre; while the average number of residential units of the areas they considered TOD were 22 residential units/acre.
NYC subway station areas have a median residential unit/acre value of 38.6, but when we exclude Manhattan stations, this value falls to 29.6. IBX station areas have 22.9 residential units per acre, which is lower than most NYC stations, even if we exclude Manhattan which has the highest values for this metric, but they can be considered average, when compared with the station areas that Renne and Ewing deemed TODs.
The highest and lowest values for this metric across the IBX stations are Metropolitan Ave. and Roosevelt Avenue stations respectively, as would be expected based on the population density.
Work Trips per Acre and Jobs per Acre
(Sources: Replica, work-purposed trips ending in the area and US Census Jobs data)
This metric shows the employment density which indicates the potential for an area to be a destination for commuting trips thus its potential to generate transit ridership.
Based on the two sources we used to calculate this metric, which yielded similar results, NYC stations range between 220 to 150 jobs and about 2 jobs per acre. The median number of jobs per station area in NYC is 21.5 (avg of two sources), excluding Manhattan, it is 16, and across the IBX stations, there are 14 jobs/acre on average, within the buffer areas. Kamruzzaman deems 20 jobs/acre (8/hectare) a minimum for a residential TOD and 160 jobs/acre (65/hectare), a minimum for an activity center TOD in Brisbane, Australia. Thus, several Manhattan station areas would be considered activity center type TODs for Kamruzzman, but most IBX station areas fall below the residential TOD threshold.
Looking at the values of this metric, and the land use metrics that follow, we can broadly comment that commercial uses and employment should be encouraged to expand around IBX stations to support ridership and make the investment to build the line, a feasible one.