The London Underground system comprises intro 11 lines, including Bakerloo, Central, Circle, Metropolitan, Northern, District, Hammersmith & City, Jubilee, Piccadilly, Waterloo & City, Victoria that serve overall 270 stations, which are operated by the Transport for London, coded as TfL.
The Underground serves around 270 stations, from which 16 Underground stations are accessible outside the London region: 8 can be reached on the Metropolitan line and other eight on the Central line. Five out of these stations serve Amersham, Chalfont, Latimer, Chorleywood, and Chesham on the Metropolitan line, while Epping serves on the Central line; Those stations are beyond the 'M25 London Orbital' motorway.
The rest 32 stations serve London boroughs; 6 stations serve Bexley, Croydon, Bromley, Kingston, Sutton, and Lewisham; However, these six stations are not provided by the Underground network, while the Hackney has Old Street, right on the Northern line Bank branch, and Manor House, available on the Piccadilly Line, is open only inside of its boundaries. Lewisham was served via the East London Line, which had stations at New Cross and New Cross Gate. However, later the station and its line were transferred to the London Overground network in the 2010s.
King's Cross St. Pancras was ranked as the busiest station on the network in 2017, which was used by 97 million passengers, while Roding Valley was the least used station, with only 368,413 passengers. The total number of annual exits and entries or all stations was 2.946 billion in 2017.
Below there is the list of those stations which reached over 33.5 million passengers during 2017:
Besides, Transport for London announced plans and aims to extend the Northern line and add two new stations to the network. More preciously, Battersea Power Station and Nine Elms are being expanded, both are served by the Northern line, Zone 1, both in Wandsworth, are dated to open by the year 2021.