High Quality Content by WIKIPEDIA articles! MARC (Maryland Area Regional Commuter) (reporting mark MARC), known prior to 1984 as Maryland Rail Commuter Service, is a regional rail system comprising three lines in the Baltimore-Washington Metropolitan Area. MARC is administered by the Maryland Transit Administration (MTA), a Maryland Department of Transportation agency, and is operated under contract by CSX Transportation and Amtrak. MARC does not operate on weekends. Service is suspended or reduced on select holidays. With some equipment capable of reaching speeds of 125 mph, MARC is considered the fastest commuter railroad in the United States.