Metropolitan line

The Metropolitan line, colloquially known as the Met, is a London Underground line between Aldgate in the City of London and Amersham and Chesham in Buckinghamshire, with branches to Watford in Hertfordshire and Uxbridge in Hillingdon. Printed in magenta on the tube map, the line is 41.4 miles (66.7 km) long and serves 34 stations. Between Aldgate and Finchley Road, the track lies mostly in shallow "cut and cover" tunnels, apart from short sections at Barbican and Farringdon stations. The rest of the line is above ground, with a loading gauge similar to those of main lines. Almost 94 million passenger journeys were made on the line in 2019.

This line is one of two Underground lines that cross the Greater London boundary and proceed outwards into the Home Counties, the other being the Central line. It is the only Underground line with an express service at peak times; the longer distance between stations means trains can achieve the system's highest speeds, up to 62 miles per hour (100 km/h), on some sections.