Central line (London Underground) interchange, it was ruled out on grounds of cost, the disruption it would cause to the Central line while being built and because the platforms would be too close to sidings at Liverpool Street and would not be developed until after Crossrail is fully operational. The developers of the "First Central" business park at Park Royal, west London, were planning a new station between North Acton and Hanger Lane. This would have served the business park and provided a walking distance interchange with Park Royal station on the Piccadilly line. This is not being actively pursued; London Underground has said
Seoul Subway Line 5 underground railway tunnels of any kind constructed. Today it is the third longest continuous underground subway tunnel in the world, just behind Guangzhou Metro Line 3 and Beijing Subway Line 10. The line was built 1990~1996 and is an important east-west link connecting Gimpo Airport, the Yeouido business area, downtown Seoul, and the Gangdong residential districts. In 1996 Line 5 was implemented with Automatic train operation. However, it was deemed that a driver would be necessary in case of a breakdown of the automation system, therefore each subway train has one driver on board. It was the world's longest underground