 Class 334 trains are powered using overhead wires at 25 kV AC.A total of 40 three car units are in use (numbered 001-040), of which 38 were delivered from Alstom trains in 1999, although due to teething problems, two extra were ordered and they did not enter service until 2001.The Class 458 is operated by South Western Railway on services from London Waterloo to Reading, Weybridge, Windsor & Eton Riverside, and circular metro routes from Waterloo via Richmond and Hounslow.