Despite its age it has one of the lowest levels of delays on the network. Signal failure is the main cause of lost time, accounting for 23% of delays, compared to a network average of 14%.
Transport for London measures delays in what it calls Lost Customer Hours (LCH). These are calculated by multiplying the delays in minutes by the number of passengers. TfL records all delays over 2 minutes. It uses the financial year from April to March and splits the year in 13 equal periods for performance measurement.
Data in the London Underground Performance Almanac for the last full year shows there was an average of 94,441 Lost Customer Hours per period on the Metropolitan line.
Along with the District, Circle, and Hammersmith and City lines a modernisation project is about to get underway on the Metropolitan including up dates to the signals system, which TfL admits “belongs in a museum” although still functions safely.