The presented table depicts vary operated time and conditions of the underground railway systems in 6 cities(London, Paris, Tokyo, Washington DC, Kyoto, and Los Angeles).
A conspicious positive correlation is evident in the length of history and route in those systems. For example, London’s railway systems started in 1863, exceeding 10 times in the kilometres of route of Los Angeles’, which opend in 2001. However, the scale of underground railway networks doesn’t translate to utilization. Particularly noteworthy is that altough the system in London is the largest, it even fail to achieve a half of passengers amount yearly by Tokyo, which is 1927, compared to 775 by London.
Several factors likely contributed to those phenomenon. One of the explainations of the correlation between operated time and route scale is that cities with long history like London and Paris didn’t pay much attention in traffic in the beginning of urbanazation because cars and other heavy vehicles were not popular back then, causing roads designed relatively narrow. After a rapid proliferation of the motor vehicles as a result of city advancement, the old cities had to develop underground railway systems to reduce traffic jam on the ground, leading expansions of railway networks. However, large systems stands for passager capacity, not passager quantity, which also decided by city population. This may explain why asian cities like Tokyo and Kyoto get unmatched numbers in passagers per year.
In conclusion, underground railway systems are indispensable in developed cities now. With the time passing by, length of railway route and passagers carrying per year are poised to increase.