British Rail Class 377

The British Rail Class 377 Electrostar is a British dual-voltage electric multiple unit passenger train built by Bombardier Transportation on its Electrostar platform at Derby Litchurch Lane Works from 2001 to 2014. The trains work suburban services in South London and main-line commuter services to Sussex, Surrey, Kent and the South Coast, replacing Class 421 and 423 slam-door stock more than 40 years old. Their air conditioning and higher power use forced upgrades to the 750 volt DC third-rail supply, and the collapse of Railtrack after the Hatfield rail crash delayed that work, so the units did not enter service until 2003. Sub-classes 377/2, 377/5 and 377/7 carry pantographs for 25 kV AC overhead lines, and the class uses Dellner couplers instead of the Tightlock couplers of the Class 375.