High Quality Content by WIKIPEDIA articles! The Fairmount Line or Dorchester Branch is a line of the MBTA Commuter Rail system in Boston, Massachusetts, USA. Except for a short portion in Milton, it lies entirely within Boston, progressing in a southwesterly trajectory, passing through the neighborhoods of Dorchester, Mattapan and Hyde Park. It sees service roughly every half hour during rush hours and every hour at other times, with no night or weekend service. Most trains reverse direction at the south end at Readville, but a few continue onto the Franklin Line or Providence/Stoughton Line. The Fairmount Line itself has only five stations - three plus the two termini, South Station and Readville; however, four additional stations are planned to be open by 2015.