This tool is for riders of the New York City Subway in New York, New York, USA.
Have you ever been riding a local train to a local stop in the New York City Subway when you saw an express train across the platform? You may have wondered whether getting on that express train would allow you to overtake a local train ahead of yours. You did not know whether you would simply end back up on the same local train when it comes to make the final leg of the trip to your stop. If you took the gamble and boarded the express train, you either saved yourself time or spent energy unnecessarily.
This tool (“Should I Cross Platform Onto Express Train,” or SICPOET) should help you in your decision. It uses realtime train movement data from the MTA’s data feed to find the fastest path from one stop to another. (Technically speaking, it constructs a directed graph and then runs Dijkstra’s shortest path algorithm on it.) This tool prioritizes the earliest arrival above all else; it assumes that all transfers can be made instantly, and if it is faster to go in the wrong direction and then double back, the tool will instruct you to do so. This is pure speed; no attention is paid to your human limitations.
Please be aware that the tool only shows trips on lines for which realtime data have been published. Neither this site nor the MTA guarantees the accuracy of the data in any way. You therefore should not rely on this tool for finding your way through the subway; rather, use it to guide you in choosing between options along your commute with which you are already familiar. If you select a start or end stop that is not served by any trains with realtime data, you will see an error message saying that the stop is invalid.
If you did not read the previous paragraph, read this: the tool does not show routes that do not have realtime data! There may be a faster way to get where you are going that involves one or more trains for which the MTA has not published live vehicle location data. Look at the name of the tool; this is only supposed to help you decide whether to get on an express or local train. For a good city-mapping app, try Citymapper.