The following is a list of all heavy rail rapid transit systems in the United States, ranked by average weekday ridership. All figures are average weekday unlinked passenger trips (i.e. line transfers on multiline systems register as separate trips). The data is provided by the American Public Transportation Association's Ridership Reports Statistics for the third quarter of 2011, unless otherwise noted.[1]
| Rank | System | Largest city served | Weekday ridership | Route length | Weekday ridership per mile | As of | Opened | Stations | Lines |
|---|---|---|---|---|---|---|---|---|---|
| 1 | New York City Subway ** | New York City | 7,820,700 | 229 mi (369 km) | 34,152 | Q3 2011 | 1904 | 468 | 24 |
| 2 | WMATA Metrorail ** | Washington, D.C. | 1,003,100 | 106.3 mi (171.1 km) | 9,437 | Q3 2011 | 1976 | 86 | 5 |
| 3 | CTA 'L' ** | Chicago | 729,100 | 107.5 mi (173.0 km) | 6,782 | Q3 2011 | 1893 | 144 | 8 |
| 4 | MBTA (or "The T") Red, Orange, and Blue Lines* and ** | Boston | 530,400 | 38 mi (61 km) | 13,958 | Q3 2011 | 1897 | 51 | 3 |
| 5 | BART* and ** | San Francisco | 381,100 | 104 mi (167 km) | 3,664 | Q3 2011 | 1972 | 44 | 5 |
| 6 | SEPTA Market-Frankford and Broad Street Lines* and ** | Philadelphia | 300,000 | 25 mi (40 km) | 12,000 | Q3 2011 | 1907 | 50 | 2 |
| 7 | PATH* and ** | New York City | 259,100 | 13.8 mi (22.2 km) | 18,775 | Q3 2011 | 1908 | 13 | 4 |
| 8 | MARTA | Atlanta | 246,500 | 47.6 mi (76.6 km) | 5,179 | Q3 2011 | 1979 | 38 | 4 |
| 9 | Los Angeles County Metro Rail Red and Purple Lines* and ** | Los Angeles | 161,000 | 17.4 mi (28.0 km) | 9,253 | Q3 2011 | 1993 | 16 | 2 |
| 10 | Metrorail ** † | Miami | 60,000 | 22 mi (35 km) | 2,727 | Q3 2011 | 1984 | 22 | 1 |
| 11 | Baltimore Metro Subway* and ** | Baltimore | 58,400 | 15.5 mi (24.9 km) | 3,768 | Q3 2011 | 1983 | 14 | 1 |
| 12 | Tren Urbano | San Juan | 37,900 | 10.7 mi (17.2 km) | 3,542 | Q3 2011 | 2004 | 16 | 1 |
| 13 | PATCO Speedline* | Philadelphia | 36,100 | 14.2 mi (22.9 km) | 2,542 | Q3 2011 | 1936 | 13 | 1 |
| 14 | RTA Rapid Transit Red Line* | Cleveland | 18,600 | 19 mi (31 km) | 979 | Q2 2008 | 1955 | 18 | 1 |
| 15 | Staten Island Railway | New York City | 14,800 | 14 mi (23 km) | 1,057 | Q3 2011 | 1860 | 22 | 1 |
Those systems marked with an asterisk (*) offer connection to a light rail system; only the parts of the systems that are not light rail are counted in the statistics presented here.
Those systems marked with a double asterisk (**) offer connections to commuter rail systems.
(†)The Miami Metrorail connects with Metromover; only figures for Metrorail are counted in these statistics