There are getting to be a lot more bicycles in the subway and the cars weren't designed to hold them. Near the exits they're a safety hazard and wherever they are they take up the space of several people. Their wheels make your clothes dirty if you happen to touch them; the chains and fenders can do worse than that. Something needs to be done to accommodate bikes (and maybe baby carriages and wheelchairs) in particular cars of the train and restrict them elsewhere.
Here are four bicycles that a family of tourists decided to bring into a single car — and chain to the poles — 18 July, 2013, 9:45 p.m. They must have entered in lower Manhattan, but the train soon got crowded. I estimate that these four bikes took up the space of 15 people.