[LeoPanthera]

It depends how you measure it.

NYC has the most stations, 424.

Shanghai has the most track, 743 km, and the most annual riders, 2834.69m.

[chrischen]

A quick Google says the Tokyo metro moves over 3.3 billion a year.

[LeoPanthera]

Perhaps that number is for "rides" and not "people".

[JCharante]

Same type of number as the one given for Shanghai, I doubt that subway system moves 2x the population of China every year worth of unique individuals.

[ant6n]

It depends on who you ask.

Ask a New Yorker, and the NYC subway is the greatest in the world (oh and PATH is not part of the subway system, cuz it's not MTA and goes to New Jersey).

Also, NYC itself is the greatest city on the world. ;-)

[remarkEon]

If I were to be the one deciding how to measure this, the “biggest” subway would be the one that moves the most people per day.

[magicalhippo]

For me, complexity would have to be a factor.

A single ring line would in my view count as smaller than a more traditional "flared out" system, assuming they moved the same amount of passengers.

Maybe a complexity factor based on number of distinct tunnels multiplied by number of riders? Hmmm, metrics are hard...

[vmception]

Nah, breadth and depth

[peterpost2]

dont forget width!