NYC subway challenge

Inspired by seeing this old article on Hacker News, here's a challenge for you: In the (current) NYC subway system, find two stops A and B such that to get from A to B, you need to take 4 trains. (This isn't 1980 anymore; I'm pretty certain there aren't any pairs requiring 5 trains.) We can set out several difficulty levels: 1. Ultra-easy version: There just has to be some time of day / day of the…