BRIT'S SUBWAY is a term used to refer to the London UNDERGROUND, also known as the TUBE. It is a rapid transit system serving a large part of Greater London and some parts of Buckinghamshire, Hertfordshire and Essex in the United Kingdom. The TUBE is the oldest UNDERGROUND railway network in the world, having opened in 1863. It is made up of 11 lines, 270 stations and 402 kilometers of track. The TUBE is operated by Transport for London and is the most popular form of public transport in the city.