Metropolitan line the top green light over a yellow light, and clear two green lights. The Metropolitan line's suburban rail character opposed to other London Underground lines is also shown by the long distances between stops. Eight of the top 10 furthest apart stations on the Underground are on the Metropolitan line. The section between Chalfont & Latimer and Chesham is the longest at , whilst the Finchley Road to Wembley Park section is the second longest, and Rickmansworth to Chorleywood the fourth longest overall. The Metropolitan line is the only London Underground line to operate an express service. Designed for commuters
London Overground than a solid single line, to distinguish it from the colour-coded Underground lines. The London Overground also uses a variant of the TfL roundel. TfL denotes its different transport modes such as London Underground or London Buses with variants of the roundel device using a range of colours, and the London Overground version consists of an orange ring with a blue bar. The roundel has its origins in a 1933 design by the London Passenger Transport Board and has spawned many variations. Unlike other National Rail stations, London Overground stations which are not served by another National Rail operator now