First/Last Mile Conduit
Bike share services are an increasingly available alternative transportation mode that provides an additional mobility network throughout cities. As cities encourage more transit use and lower car dependency, the bike to transit intermodal model becomes particularly important in achieving environmental and socioeconomic balance. First/last mile solutions connect people to transit options outside of a station's 1-mile catchment area. The disconnect that communities encounter often results in car dependency, which provides an undue economic burden on the lower income citizen and negatively impacts the environment.
This study investigates the relationship between Citi Bike and subway ridership in New York City and how Citi Bike end and start stations affect ridership boardings and alightings of corresponding subway stations.
For this project's scope I analyzed the entire year of 2018 Citi Bike ridership. The aggregate trips for the year 2018 in Citi Bike were 20,551,697. Due to the large data frame size, Citi Bike data was computed in Jupyter Lab using python script. The data was concatenated to show each station's longitude, latitude, start counts, and end counts in addition to the trip duration and user type. Due to the high volume of unique trips, only origin-destination pairs that acquired more than 1,500 trips were presented in the Citi Bike Origin Destination Trip Matrix map.
Subway Ridership & Citi Bike Route Analysis
As displayed in the Subway Ridership & Citi Bike Trip Routes 2018 map, higher subway boardings per station rates correspond with Citi Bike trips, suggesting that ridership provides a first/last mile linkage. The Dekalb Ave station (Inset D) has relatively high subway boarding, and a high level of Citi Bike trips extending east into the low transit serviced Fort Greene neighborhood. This Citi Bike route trend is also seen in Williamsburg (Inset C) radiating around the highly utilized Bedford Avenue and Graham Avenue stations. Citi Bike trips extend to areas with fewer and more dispersed subway connections. Additionally, Astor Place and Union Square stations (Inset B) have high levels of trips reaching eastern Manhattan, again in neighborhoods with limited subway services. Similar but less distinct trends are present along with the Nostrand Ave station radiating into central Bedford Stuyvesant and Ditmars Boulevard station in Astoria. Stations that appear to correlate with high levels of Citi Bike routes also have relatively high boarding rates. Spatial analysis suggests that Citi Bike is potentially used as a first and last/mile connector to people further from subway stations.
Subway Ridership & Citi Bike Station Proximity Analysis
The Subway Ridership & Citi Bike Station Proximity Count 2018 map shows no significant trend on subway boarding levels against the number of Citi Bike stations within proximity to the subway station. High numbers of subway boarding within midtown and downtown Manhattan appear to have a relationship between ridership and docking station counts. Still, the apparent trend is unlikely to be significant due to the high volume of commuters within those areas.
Multivariate regression analysis was conducted on the correlation between the start count and end count for Citi Bike ridership and subway boarding and alighting counts. In the analysis, coefficients remained relatively the same across each Citi Bike start and end counts, at 0.4 with a 35% prediction power based on the adjusted R-squared. This indicates that subway ridership increases as corresponding Citi Bike stations increase in trip starts and ends.
However, when multivariate regression analysis was conducted on the number of Citi Bike stations within the 0.125 buffer surrounding the subway station, no significant correlation was found. This implies that subway ridership is not influenced by Citi Bike infrastructure alone.
Spatial and statistical analysis suggests a direct and positive correlation between subway ridership and Citi Bike ridership within proximity to subway stations. The maps in Figure 2 and Figure 3 visually show spatial trends that indicate high numbers of Citi Bike routes are used as conduits for first/last-mile connections. Increased Citi Bike ridership supports subway ridership. However, there is no statistical significance between the number of Citi Bike stations within a 0.125 buffer of a subway station and ridership rates. These statistical patterns indicate that promoting ridership is more important than strategically placed Citi Bike infrastructure when addressing first/last mile solutions.
Citi Bike has announced a sizable expansion of docking stations and services that will be fully implemented by 2023. The plan extends services further into Queens and Brooklyn as well as into upper Manhattan and South Bronx, as displayed in the Citi Bike Planned Phase 3 Expansion 2019-2023 map.
The map Subway Access, 2018 Citi Bike Stations & Bicycle Infrastructure (ride.citibikenyc.com) illustrates the current conditions of subway access within a 7-minute walking catchment area in and around the 2018 study area. The areas outside the study zone, where Citi Bike service will expand in the future, have larger gaps between subway stations. This more disparate access to subway stations indicates a higher need for first/last mile solutions that Citi Bike expansion could provide.
The Subway Access, 2018 Citi Bike Stations & Bicycle Infrastructure map also displays the existing bike path network encompassing protected lanes, striped lanes, and sharrows. The protected lanes offer the highest level of safety by providing a physical barrier that separates the cyclist from traffic. The striped lane, which separates and designates a path exclusively for cyclists, is slightly less safe compared to the
protected bike lane but still effective. Sharrows
provide the least protection for cyclists
by marking the pavement in the street with a bicycle icon to indicate the safest place within active traffic to ride. Areas that reside outside of the 2018 study area have significantly fewer bike routes, low levels of protected or striped bike lanes and almost no sharrows.
As outlined in the statistical analysis, Citi Bike infrastructure alone does not drive Citi Bike ridership rates. A 2019 survey conducted in England found that safety concerns were the highest-ranking factor in why people chose not to ride a bike in the city. The survey found that 24% of people avoided riding a bike due to road safety concerns. Another 16% cited that too much traffic and traffic were going too fast (Department for Transport, England 2019). This suggests that perceived safety and safety infrastructure, such as bike lanes, traffic calming, and pedestrian leading intervals, can impact a citizen's inclination to choose bicycling as a mode of transportation.
For Citi Bike to be an effective first/last mile conduit, Citi Bike users must have access to safe bicycle routes and street conditions that can increase ridership. Citi Bike should work with the NYCDOT to collaborate on increasing bicycle infrastructure throughout these new service areas. By doing so, cycling for all citizens,
Subway Access, 2018 Citi Bike Stations & Bicycle Infrastructure
not just Citi Bike users, will become safer. Improved bicycle infrastructure will also address some of the trepidation that citizens have about riding a bike in the city and make it more likely that citizens who need a first/last mile connector will take advantage of Citi Bike services as a solution.