the London area were amalgamated to form the London Passenger Transport Board, generally known as London Transport. The railway was known as the "Central London Line", becoming the "Central line" in 1937. The 1935–40 New Works Programme included a major expansion of the line. To the west new tracks were to be built parallel with the Great Western Railway's New North Main Line as far as Denham. To the east, new tunnels would run to just beyond Stratford station, where the line would be extended over the London & North Eastern Railway suburban branch to Epping and Ongar in Essex, as well as a new underground line between Leytonstone and Newbury Park mostly under Eastern Avenue so as to serve the new suburbs of north Ilford and the Hainault Loop. Platforms at central London stations were to be lengthened to allow for 8-car trains. Construction started, the tunnels through central London being expanded and realigned and the stations lengthened, but it proved impossible to modify Wood Lane station to take 8-car trains and a new station at White City was authorised in 1938. The line was converted to the London Underground four-rail electrification system in 1940. The positive outer rail is higher than on other lines, because even after reconstruction work the tunnels are slightly smaller. Most of the tunnels for the extensions to the east of London had been built by 1940, but work slowed due to the outbreak of the Second World War until eventually being suspended in June. The unused tunnels between Leytonstone and Newbury Park were equipped by the Plessey Company as an aircraft components factory, opening in March 1942 and employing 2,000 people. Elsewhere, people used underground stations as night shelters during air raids. The unopened Bethnal Green station had space for 10,000 people. In March 1943, 173 people died there when a woman entering the shelter fell at the bottom of the steps and those following fell on top of her. Post war Construction restarted after the war, and the western extension opened as far as Greenford in 1947 and West Ruislip in 1948. The powers to extend the line to Denham were never used due to post-war establishment of the Green Belt around London, which restricted development of land in the area. The eastern extension opened as far as Stratford in December 1946, with trains continuing without passengers to reverse in the cutting