How The Mind-Bogglingly Complex Subway Stays Running

Within just over 20 years, Shanghai’s subway system has become the largest in the world, at 617 km. Just how does this expansive, not to mention complicated, puzzle get maintained?

 

After the lights of all but the latest-night bars have gone out, the engineers of the Shanghai subway toil into the night, making sure one of the world’s most complex subway systems continues to serve its daily ridership of 10 million.