The 1800 series was introduced in 1991 as two-car commuter-style sets to be coupled to six-car 1000/1200 series sets on limited express services during the busy peak hours. Sets are also used on their own or in pairs on other services.
Formations
, the fleet consists of nine two-car 1800 series sets and two two-car 1850 series sets, formed as follows.
The 1800 series trains were first introduced in 1991, to augment the 1000/1200 series trainsets. In 1992, three more two-car sets were built, reusing the underframes and electrical equipment from withdrawn 7500 series "Panorama Car" EMU cars.
Refurbishment
From 2017, the fleet underwent a programme of refurbishment. The first 1800 series set to be refurbished and reliveried was 1808 in May 2017.