One of the most interesting things I learned about subway systems while researching for this post is that no one agrees on how long subway systems are. The world’s longest subway system is given by different sources as that of Seoul, Shanghai, Beijing, or London.
Part of the discrepancy can obviously be accounted for by time: the longest subway system in 2002 won’t necessarily hold that record in 2014. But when the site updated in 2003 that claims London is the longest gives its length as 415km, whereas the official Transport for London site currently says 402km—what gives? In this case, I’m tempted just to shrug and chalk it up to human error. But the Seoul subway system is sometimes cited as having a total length of over 900km, making it easily the longest subway system in the world, when other sources give the length of the complete system (it’s run by several different companies, which only adds to the confusion) as between 450-650km. It could be because some are measuring total track length, whereas others are using total route length. The second method makes more sense, since having two lines of track next to each other on the same route doesn’t allow you to travel any farther! Given that distinction, my bet’s on Beijing or Shanghai for the true record-holder—depending on who’s expanded more recently at this point.
The shortest subway is less disputed: the Tünel in Istanbul, Turkey runs on a route of (probably) only 573m (1,880ft). The length is variously given as 554.8m, 573m, and 606.5m; since the English version of the official website doesn’t have the information at all, I chose the one that was both the median and mode as far as the sources I checked were concerned.
The oldest and perhaps most well-known metro system in the world is the London Underground, which first opened as an underground railway in 1863. Operation began on the first electric underground railway in 1890. Despite its name, less than half of the Underground is actually subterranean.
So what makes a subway a subway? If 55% of the iconic Tube is aboveground, where’s the cutoff point? Well, first off, in most of the UK, the word subway doesn’t refer to a rapid transit system but rather a pedestrian underpass below a road or other obstacle. So hardly anyone calls the London Underground by that term. That aside, there is, unsurprisingly, no universal definition for what constitutes a subway. It’s generally lumped in with other names for rapid transit systems, like metro, U-Bahn, and (by some definitions) heavy rail. What any given system is called changes more by locality than by specs.
They are, however, all distinguished from a light rail, which shares right-of-way with street traffic rather than running on its own separate system.