In the United States only four systems offer service 24 hours per day and 365 days per year: the New York City Subway, the Chicago 'L' system, PATH trains, .
A subway party is a celebration that occurs on a mass transit system. Generally, people meet at a predetermined station in their city's mass transit system, wait until their numbers have achieved critical mass, and board the train. From there, revelers may engage in many different activities, from playing music and dancing to exchanging gifts.