To wait or not to wait, that is the question that engineer Erik Bernhardsson answered in his recent analysis of the MTA’s real-time API. In his post titled NY Subway Math he determined that if you’re in a hurry, you should only wait for a train to arrive for 11 minutes (h/t Technically). At this point, the chance that there’s a serious delay begins to rise. As he notes, “The interesting conclusion is that after about five minutes, the longer you wait, the longer you will have to wait. If you waited for 15 minutes, the median additional waiting time is another 8 minutes. But 8 minutes later if the train still hasn’t come, the median additional waiting time is now another 12 minutes.”
Bernhardsoon started looking at the data to “understand if to what extent waiting for a subway is ‘sunk cost’ vs. an investment.” He illustrates this in the graph above, where you can see how long you’re likely to wait for a train based on how long you’ve already waited. The blue line is the median, and the yellow is the 90th percentile. On a normal day, you’ll wait less than five minutes, but 11 minutes is where you’ll hit that dreaded yellow line that makes mechanical issues, sick passengers, and the like much more plausible.