answers: 1883
context: class numbers begin with a '3', Southern Region 3rd rail DC EMUs with a '4' and other DC EMUs with a '5'. In the late 1960s, the need for a new EMU design was recognised. Prototypes of the "British Rail New Generation", "1972" or "PEP" design were built and placed in passenger service in 1971. Built from aluminium, with all vehicles powered and employing rheostatic braking, the production units were built by BREL York Works with two sets of air-operated doors on the sides of the car and fully automatic tightlock couplers. The first units were the dual voltage Class </s> 1963. The Metropolitan Railway was opened in 1863 with wooden carriages hauled by steam locomotives, but at the start of the 20th century the railway was seeing increased competition in central London from the new Underground Electric Railways of London (UERL) tube lines and the use of buses. The use of steam underground led to smoke-filled stations and carriages which was unpopular with passengers, and conversion to electric traction was seen as the way forward. Because of the jointly operated "Inner Circle" co-operation with the District Railway was essential. A jointly owned experimental train of six coaches was tested on </s> 36% uses the 660/750 V DC third-rail system. The electrified network is set to expand over coming years, as 25 kV electrification is extended to currently unelectrified lines, such as the Great Western Main Line, the Midland Main Line and lines in the North of England as part of the Northern Hub. The first electric railway in Great Britain was Volk's Electric Railway in Brighton, a pleasure railway, which opened in 1883, still functioning to this day. The London Underground began operating electric services using a fourth rail system in 1890 on the City and South London Railway, now part
question: when were electric trains introduced in the uk