You can always count on repair-related disruptions with the subway system, but white signs posted in the stations and on the trains describe stations and trains affected. There are also maps posted in every station and somewhere on every train, but not nearly enough. Once through the subway entrance turnstiles, you may have to wait until you are on the train to consult a map. Some stations are marked only by a sign with the station name and the lines that pass through it. Lines are identified by a letter or number, a color, and the endpoints of the line.
Local service makes all stops, while express service skips several stops at a time.
Check your map to determine which lines are which, or you may end up in the Bronx when you wanted to stop on the Upper West Side. On the subway map, every station lists the trains that stop there. If a letter or number is printed in bold typeface, the line always stops at that station. Light typeface signifies that the line does not operate at all times or that it sometimes skips that station. There is a key to these exceptions in the upper right corner of the subway map.