How often do you get onto a packed train?

Transporting people and freight has always been a challenge for city planners around the world. To cope with the ever-increasing number of commuters, city planners are going underground to create networks that transport people efficiently.

Some noteworthy tunnels:

As cities continue to grow, the effectiveness of transportation directly impacts the quality of life for city dwellers. It is important for city planners to keep planning ahead before the demand becomes overwhelming.