Copley Outbound T Exit
If you're taking the Green Line from Park Street to Copley Square you end up exiting up the street at a different location than the inbound trains. The outbound trains end up under the intersection of Boylston Street and Dartmouth Street. The inbound train ends up near the Boston Public Library Main Entrance.
What's tricky is that as you walk through the terminal, there's no clear indicator on where you appear at street level. This is important because you don't want to exit to street level and then find that you have to cross the street because you came out of the wrong door.
The exit are separated by Dartmouth Street, and the exits are on opposite sides of the street.
Check out this picture:
There are no signs to indicate where the exits will take you!
You should go left if you want to go to the Boston Public Library, visit the Boston Marathon Finish Line, Apple Store or the Old South Church. Exit right if you want to go to Copley Square, Trinity Church and CVS.
Perhaps someday the MBTA will put up a sign to help people navigate out of the station properly.
Note: Some people may think this is a silly blog post. But it can be frustrating when you arrive at the station and have no clue on which exit to take.