The Central Line suffered the highest level of delays of any line on the Tube network in 2014/15. Apart from industrial action, which happens in one off events, the biggest cause of delay was train fleet problems. This accounted for more delays on the Central Line than any other.
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 410,144 Lost Customer Hours per period on the line. That is 29% higher than the second most delayed line, the Jubilee.
Over the past 10 years as Lost Customer Hours have been reduced across the network the Central line has remained a persistent offender. It has shown the least improvement in all lines since 2003/04.
The Central Line opened in in 1900 and its flat fare of 2 old pennies from Bank to Shepherd’s Bush earned it the nickname of the Tuppenny Tube. In the 1990s it became the second line after the Victoria to introduce automated operations where the train is largely controlled by a computer system monitored by a driver. Unlike the Victoria Line, automated operations are not a significant cause of lost hours on the line.