What is the name of the longest subway system?

NYC i believe

AnswerNew York City is the correct answer only if by "longest" the questioner means the longest by miles of track. The Metropolitan Transit Authority reports that the system currently has "approximately 660 miles" of track in "revenue service" - in other Words, serving passengers. (Another 180 miles of track is in "non-revenue service," such as in subway yards.) By that measure the system dwarfs all others in the world. However, it's also deceptive. New York's subway is the world's only system that offers extensive express service, meaning that almost every line consists of four tracks rather than two.

A more intuitive measure of "longest" subway is miles of route, which gives a much better idea of how much territory a system covers. By that measure, Shanghai is the current winner, at 260 miles. London comes in second at 258 miles, followed by New York (228) Tokyo (181), Seoul (178), and Madrid (176).

For more, please see urbanrail.net, the most authoritative on-line source for subways (I'm not affiliated with the site - just a user).

Since April 10 2010, Shanghai has become the holder of this record with 420 km of route, carrying more than 5 million passengers per day.