No More Pan Am District 4

As of October 2, 2010, there is no longer a District 4 on Pan Am Railways.  District 3 now covers everything west from about MP312.  It was always helpful having a district change half way between Ayer and Hoosac Tunnel.  When chasing a freight, you could tell just how far it had gone even if you didn't catch what milepost it was near.  Now, you better have a clue about those mileposts!