Mapping New York's Hidden Transit Demand

Traditional transit in New York is fairly easy to monitor, and newer systems such as CitiBike share their data publicly for analysis. The city's transit mix is much more complicated however, and to truly get an idea of what's going on you need to analyze more informal systems. The New Yorker recently surveyed the city's informal dollar van system. You can easily see the established routes making their way through traditionally underserved areas.

I was interested in an even more informal and less well defined system: taxi shares. Companies like Uber and Lyft did not discover cab sharing, they simply provided a way to formalize it. Before these technologies existed, those in the know could simply wait by a bus stop and expect a livery cab to come more frequently than a city bus. Once the cab fills up, each passenger pays $2, and gets taken to the nearest subway station.

I knew this informal arrangement existed on 108th St in Forest Hills, roughly between the Long Island Expressway and the Forest Hills-71st express stop, and was curious if it existed elsewhere. The smaller scale nature of it would make it harder to find established routes. Now that borough taxis have been centralized, taxi GPS data can now be reliably collected for the outer boroughs. Thanks to the legwork Chris Whong did FOILing the data, I was able to visualize potential routes.

Using trips during the month of June 2014, I searched for cab rides that ended at subway stations. I limited my search to the morning rush hour (7AM - 10AM), since it's easier for spontaneous routes to develop when everyone is heading to a central subway station. 

To try to establish a pattern, I first checked out the route along 108th St I knew about:

108th Street pretty clearly shows up as a cluster. Looking at other stops, guesses can be made about where similar cab sharing might be going on. Two stops down in Kew Gardens, for example, a stronger pattern emerges coming from the south, and potentially the east:

In addition to smaller express stops, there was a similar pattern around the terminus at Ditmars:

And Clark St, which seems to be an alternative to the F and G lines in South Brooklyn:

Major express stops would probably require a bit more research. Roosevelt Ave in Jackson Heights for example had a large volume of cabs flowing towards it:

There could perhaps be a few routine lines here, but it seems a bit more evenly spread out. You can see a similar pattern with Atlantic Avenue in Brooklyn:

And E 180th Street in the Bronx:

Check out the full map below(or click here to open in a new window). Click on the stations to filter cabs terminating there and try to find anything I missed. I'd be interested to hear from anyone who has experience with these shares!