Shinjuku is often referred to as the world's busiest station in terms of daily passenger throughput. The station acts as a hub to connect rail traffic between central Tokyo and its western suburbs through a range of inter-city rail, commuter rail and metro lines.

The title of the "busiest train station by the number of trains" traditionally belongs to Clapham Junction in London, England. While it is not the busiest by passenger volume (that title usually goes to Shinjuku in Tokyo), Clapham Junction handles an incredible 100 to 180 trains per hour during peak times. It serves as a massive interchange where the lines from London Victoria and London Waterloo converge, meaning nearly every train heading to the south and southwest of England passes through its 17 platforms. In 2026, the station remains a marvel of scheduling, with a train arriving or departing roughly every 20 seconds. If you measure "busiest" by platforms, the title goes to Grand Central Terminal in New York with 44 platforms. However, in terms of sheer "traffic density" and the technical challenge of moving hundreds of heavy rail services through a single throat every single hour, Clapham Junction is the undisputed global leader, often referred to as the "Gateway to the South."