The A line and the C line have the same route in the subway system. The C uses the local track and stops at every station. The A is the Express. I need local so I get on the C sit on the bench and see the A pull in into the station on the Express track on the other side of the platform. We do this for a couple of stations. Then we approach 72nd Street. Suddenly the A train is on the track right behind me. Somewhere between 59th and 72nd in the dark tunnels of the subway system we must have crossed each others tracks. Very scary. I had suspected this behavior earlier but never saw it so blatanly. I call it magic.