The Providence and Worcester Railroad shares tracks with Providence/Stoughton Line trains between Providence and Wickford Junction; it uses a freight-only track between Providence and Central Falls. No freight operates on the Needham Line, the Northeast Corridor between Readville and Back Bay, the Old Colony mainline between Boston and the Greenbush Line junction in Braintree, the Plymouth/Kingston Line, and most of the Greenbush Line. CSX also operates on most northside lines; prior to its 2022 purchase by CSX, Pan Am Railways operated over these lines. Pan Am Southern (planned to be replaced by the Berkshire and Eastern Railroad) operates over the Fitchburg Line west of Ayer. Their combined Freight Main Line between Mechanicville, New York, and Mattawamkeag, Maine, shares tracks with sections of the Fitchburg, Lowell, and Haverhill lines. No freight service is operated over the Newburyport/Rockport Line north of Salem. Weight limits and loading gauge vary across the system. The full Framingham/Worcester line is rated for car weights of , sections of lines that are part of the Freight Main Line for , and other lines for lower weights. The western portion of the Framingham/Worcester Line and the southern section of the Providence/Stoughton line can accommodate cars up to (AAR Plate H or Plate K). The Fitchburg Line west of Ayer can accommodate cars up to (AAR Plate J), while most of the other northside lines can accommodate up to (AAR Plate F). The inner Fitchburg and Newburyport/Rockport Lines, and the southside except for the outer Framingham/Worcester Line, have height restrictions smaller than Plate F. Fares MBTA Commuter Rail uses a zone fare system, with fares increasing with distance. Zone 1A includes the downtown terminals and other inner core stations up to about from downtown. Ten additional zones, numbered 1 through 10, extend outwards from Boston. Each zone is about 5 miles, with most outer terminals in zones 6 through 8. Only two stations use further zones: in Zone 9, and in Zone 10. Zone 1A fares are identical to MBTA subway fares (though subway passes on CharlieCards are not accepted, except for Fairmount Line stations that have CharlieCard validator machines). , one-way fares within Zone 1A are $2.40, while fares between further zones and Zone 1A range from $6.50 for Zone 1 to $13.25 for Zone 10. Trips that do not enter Zone 1A have less expensive interzone fares; , these range from $2.75 for travel within a single