Hi there, this is my first post here so I apologize if there's anything I did wrong.
Anyway, I have been curious about this ever since I moved to the city last year. I live near the terminus of a train, and I've noticed that every time a train enters or leaves the station, it lets out a very loud hiss after it brakes. It sounds like a large burst of air. I've been paying attention at other stations and it seems that trains on other lines do this at their first and last stop as well, but I've never heard it at intermediary stops. What causes them to make that noise?
Thanks!
