In 1900 the British Westinghouse Electrical & Manufacturing Co Ltd bought land in Trafford Park and built a factory which went into production in 1902 for the manufacture of mechanical and electrical equipment for the generation, transmission and use of electricity. In 1919, Trafford Park Works became owned by British Westinghouse’s successor, Metropolitan-Vickers Electrical Company (MV). The main shops, in common with factory construction throughout Trafford Park, were single floor type, with bays 1,000 feet in length, and had direct railway communication with the docks and trunk systems of the country. The main office block was a copy of the Westinghouse building in Pittsburgh, USA and the factory was to the American design and used imported steelwork for construction. Products manufactured at the Works included gas engines, stationary steam engines, electric generators, transformers, switchgear, meters, motors, control gear, and arc lamps. During the First World War, British Westinghouse built some small petrol-electric locomotives for the War Department Light Railways. In 1928 the Works were taken over by Associated Electrical Industries (AEI), which merged Metropolitan-Vickers and British Thomson-Houston, though these two companies continued their own trading names. Traction design and manufacture was always a minority of the workload at Trafford Park with the largest operations generally turbine manufacture. Very few vehicles were built there, and traction machines (i.e. motors, inductors and generators) were largely built in other places – notably at Sheffield or Rugby. Trafford Park traction manufacture was largely that of assembling control gear – contactors, switches, drivers’ controllers, camshaft controllers, relays etc. and building these into frames or equipment boxes for installation in vehicles made elsewhere. An important part of the Trafford Park Works site was the general switchgear operation, mainly for generation or distribution installations. The on-site Switchgear Testing Company was a “testing house” for these products and contributed to testing and development of traction circuit breakers and switchgear. During the Second World War MV acting for the Ministry of Aircraft Production produced more than a thousand Lancaster Bombers in the adjacent Mosley Road building. The company also manufactured war munitions and in the laboratories developed what became known as Radar. In 1959 the newly formed AEI Traction Division established its headquarters at Trafford Park, with a product range that included electric and diesel-electric locomotives; electrical equipment for tram-cars, trolley buses and trolley mining locomotives and traction motors. AEI was taken over by the General Electric Company (GEC) in 1967 whose Witton Works closed in 1969, with the design office and traction manufacture transferred to Trafford Park, as a result of the GEC reorganisation and mergers. GEC Traction Ltd took over the Works in 1972. In 1990 the former Low Voltage Switchgear site at Trafford Park (West Works) was renovated to be the new manufacturing facility for GEC Alsthom Traction, with an electronics workshop, machine shop and plating baths, and an assembly shop for switchgear, equipment cases and power modules. This building was vacated in 1998 when power modules and switchgear was moved to Tarbes in south west France. The Works housed the administrative, commercial and accounting functions, the majority of the design departments and the development section with its associated workshops and laboratories. The manufacturing area was devoted primarily to the production of components of traction control and railway signalling equipment. In 1993, as part of the rationalisation of the equipment group, it was announced that the headquarters of GEC Alsthom Traction would move to Preston, leaving only Power Module design and manufacture at Manchester, with the eventual closing of all activities at Trafford Park in 1998. The iconic original Westinghouse building was demolished and the site is now (2015) largely devoted to container handling and logistics operations.

In 1910 the state-owned South African Railways and Harbours (SAR&H) organisation was created, after the four colonies of the Cape, Natal, Transvaal and the Orange Free State were amalgamated into the new Union of South Africa. In 1916, SAR&H took over the activities of the Central South African Railways, the Cape Government Railways and the Natal Government Railways. In 1924 the last privately owned railway line in South Africa was taken over by SAR&H; the New Cape Central Railway between Worcester and Voor Bay. In 1920 electrification of South Africa’s railways was completed, and in 1924 the first electric test train ran between Ladysmith and Chieveley in Natal. In 1950 the first portion of the new Johannesburg station was opened and construction was completed on the huge workshops complex at Koedoespoort. In 1960, diesel locomotives were introduced on a large scale to SAR&H. In 1981, SAR&H changed its name to South African Transport Services (SATS) and took on South Africa’s railway, harbour, road transport, and aviation and pipeline operations.

Metropolitan-Vickers Electrical Co Ltd was the new trading name given to British Westinghouse Electric and Manufacturing Co on 8 September 1919. The predecessor company had sold its controlling share to the Metropolitan Carriage Wagon Co in 1916 in order to gain membership of the Federation of British Industries. In 1919, Vickers acquired the Metropolitan Carriage Wagon Co, along with its controlling share in British Westinghouse, prompting the change in name to Metropolitan-Vickers Electrical Co Ltd. The American owned British Westinghouse had established its English operations at Trafford Park in 1899, and Metropolitan-Vickers Electrical Co Ltd continued on the same site from 8 September 1919. The company was initially known for its electricity generators, later diversifying into the manufacture of steam turbines, switchgear, transformers, electronics and railway traction equipment. The passing of the Electricity (Supply) Act in 1926 provided a boost to the company’s post-war fortunes, with the creation of the National Grid generating demand for the company's products. In 1928, Metropolitan-Vickers Electrical Co Ltd merged with its rival British Thomson Houston Co Ltd, retaining both names for trading purposes. The following year, on 4 January 1929, Associated Electrical Industries Ltd (AEI) acquired Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd. Again, both trading names were retained, and a fierce rivalry was established between the firms which the parent company was unable to control. In 1931, Sir Felix Pole joined Metropolitan-Vickers Electrical Co Ltd as its new chairman. He oversaw a period of expansion for the company leading into the Second World War. In 1939, seeking a more concise name for the company, the Board of Directors decided upon Metrovicks, which became interchangeable with the official company name of Metropolitan-Vickers Electrical Co Ltd. Under Sir Felix Pole's chairmanship, Metropolitan-Vickers developed new products for the aviation industry and during the war was one of the sites where Lancaster bombers were built. In 1941, the company developed the first British axial-flow jet engine, the Metrovick F.2. Following the Second World War, the company appointed Oliver Lyttelton as chairman, with the aim of increasing the efficiency and productivity of AEI. Despite his success in achieving this aim, Lyttelton was unable to resolve the commercial rivalry between Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd. During his second period as chairman, from 1954-1963, Lyttelton, now Lord Chandos, oversaw the development by Metropolitan-Vickers Electrical Co Ltd of the first commercial transistor computer, the Metrovick 950. Chandos also resolved to extinguish the competition and internal divisions between Metropolitan-Vickers Electrical Co Ltd and the British Thomson Houston Co Ltd, and both company names ceased to be used from 1 January 1960, with all subsidiaries going on to trade under the name of Associated Electrical Industries Ltd.

The Transport Act 1947 nationalised virtually all British transport, including the railways, waterways, and road haulage. These were transferred to a newly-created operating body, the British Transport Commission (BTC). The British Transport Commission began operations on 1st January 1948, under Chairman Sir (later Lord) Cyril Hurcomb. At this time, the British Transport Commission acquired the “Big Four” grouped railways, with virtually all minor railways as well, together with the London Passenger Transport Board. This automatically transferred the assets of the rail companies to BTC, including ships, ports, hotels, and investments in bus, coach, and haulage companies. Two bus companies, Tilling and Scottish Motor Traction, were soon added, as well as long-distance road hauliers. The Transport Act charged the British Transport Commission with the task of charged with “integrating” various forms of transport into single public service. The British Transport Commission did not directly operate transport services. Operations were delegated to five separately appointed executives: Docks and Inland Waterways, Hotels, London Transport, Road Transport, and Railways. The Railways Executive operated under the name British Railways. In 1949, the Road Transport Executive was divided into two separate executives: Road Haulage and Road Passenger. The Commission exercised financial control over these Executives, and managed them through schemes of delegation. The Commission attempted to fulfil its statutory duty to “integrate” public transport by introducing Area Schemes. These were designed to establish regional monopolies for road passenger transport, ports, and harbours. “Integration” was also to be promoted through Charges Schemes, in which the true costs of different modes of transport were to be reflected in the charges. This was designed to attract traffic to the most economic and efficient mode of transport. The structure of Executives was dramatically altered by the Transport Act 1953, which abolished all Executives, with the exception of London Transport. Responsibility for the operation and maintenance of transport systems was delegated to the chief regional managers. The railways were reorganised into a system of area boards for each of its six regions. In September 1953, Sir Brian Robertson became Chairman. Disposal of the haulage fleet also began at this time, but a lack of buyers made this difficult. Rising costs, industrial action and competition from road traffic meant that the British Transport Commission was in financial trouble by 1955. It sought relief from this by publishing The Modernisation and Re-equipment of British Railways, a plan which proposed an investment in the railways of £1,240m over fifteen years. The main features of this plan were the replacement of steam with electric and diesel traction, the electrification of principle routes, and the introduction of new coaching stock. Despite the modernisation plan, the financial position of the British Transport Commission worsened. Two government reviews, in 1956 and 1959, concluded that the Commission was unwieldy and had an insufficiently commercial outlook. Sir Brian Robertson retired in May 1961, and was replaced by Dr Richard Beeching. The BTC was abolished by the Transport Act 1962. It was replaced with five new authorities that were answerable to the Minister of Transport: the British Railways Board, the British Transport Docks Board, the British Waterways Board, the London Transport Board, and the Transport Holding Company. Dr Beeching became chair of the British Railways Board.

GEC Traction (GECT) was formed in 1972 as part of the GEC Power Engineering Group following earlier amalgamations of the traction divisions of the General Electric Company (GEC), the English Electric Company (EE) and Associated Electrical Industries (AEI). A wholly owned subsidiary company of GEC, the company had offices and works, located at Trafford Park in Manchester, at Strand Road in Preston, and at Attercliffe Common, Sheffield. The headquarters of GEC Traction was Trafford Park, Manchester (previously the headquarters of English Electric-AEI Traction) with design of rotating machines at Preston and Sheffield, and manufacturing activities for control equipment at Manchester and Preston. GEC Traction designed and manufactured a full range of traction machines and control equipment for electric vehicles, including electric locomotives and multiple unit trains for main-line and mass-transit railway systems (dc up to 3,000 volts, and ac up to 50,000 volts), diesel-electric locomotives and trains, mining and industrial locomotives, tramcars and trolleybuses. GEC Traction was the leading supplier of traction equipment in the UK and had a wide market around the world, particularly in South Africa, Australasia, Hong Kong, South Korea, South America and Pakistan. In 1979 the Industrial Locomotive Division of the former English Electric which was based at Vulcan Works, Newton-le-Willows was merged into GEC Traction, which later became a separate company, GEC Industrial Locomotives Ltd. During the late 1980s and 1990s the firm underwent major rationalisation, involving closure of several sites including Attercliffe Common in Sheffield in 1985 and the company’s headquarters at Trafford Park in Manchester in 1998. The company name GEC Traction endured until a merger with the French Alsthom group in 1989, which created GEC Alsthom Traction, which was still a branch of the main company GEC Alsthom.

Córas Iompair Éireann (CIÉ) was formed as a private company under the Transport Act in 1944 and incorporated the Great Southern Railways (GSR) and the Dublin United Transport Company. CIÉ was nationalised and changed to a corporation status under the Transport Act in 1950 by merging with the Grand Canal Company. CIÉ railways became Iarnród Éireann in the mid 1980s.