The MetroRail (commonly referred to as the Metro) is the rapid transit system used in the Washington D.C. area. It is administered by the Washington Metropolitan Area Transit Authority (which also operates MetroBus). It services Montgomery County and Prince George's County in Maryland as well as Fairfax County, Arlington County, and the City of Alexandria in Virginia.
Since 1976 it has grown to include 5 lines (with a 6th in the construction stages), 86 stations, and 106.3 miles of track. It is the 2nd busiest transit system in the United States, after the New York City Subway. In 2008, 215.3 million trips were taken on the MetroRail.
Passengers enter and exit the transit system using a wallet sized, stored value, paper card with a magnetic-strip. Frequent riders often use a SmarTrip proximity card. Fares vary on time of day and distance travelled.