In , the system had a ridership of , or about per weekday as of , making it the third-busiest heavy rail rapid transit system in the United States, in number of passenger trips, after the New York City Subway and Chicago "L", and the fifth-busiest in North America. In June 2008, Metro set a monthly ridership record with 19,729,641 trips, or 798,456 per weekday. Fares vary based on the distance traveled, the time of day, and the type of card used by the passenger. Riders enter and exit the system using a proximity card called SmarTrip.
