On each train, the cab car is attached at the end closest to the downtown Boston terminal station for the particular line (either North or South Station), and the locomotive is attached at the end farthest from the terminal station. On each train serving the North Station lines, the "ADA" coach used to carry mobility-limited persons is attached next to the locomotive, allowing level boarding at all suburban stations featuring mini-high platforms. On the other hand, on each train serving the South Station lines, the cab car also serves as the "ADA" coach. (The "ADA" coaches support compliance with the Americans with Disabilities Act of 1990.)