the new york city subway is a rapid transit system that is in new york city, united states. it is run by the metropolitan transportation authority (mta). it is one of the biggest rapid transit systems in the world, with 472 stations. it has 245 miles (or 394 km) of routes on 691 miles (or 1112 km) of railway track. the new york city subway almost never closes; the trains run 24 hours a day, 7 days a week, all year. the system has only closed three times, most notably during the september 11 attacks and when hurricane sandy flooded its tracks.