By 1914 the pattern of Glasgow's railway network had been set. It was owned by the Caledonian (CR), Glasgow & South Western (GSWR) and North British (NBR) railways, and by the Glasgow District Subway, with its circular underground route. Since the electrification of the tramways in 1898-1902, the suburban rail routes had suffered badly from competition, halting further development. The east-west lines through the city centre were particularly badly hit and several stations closed between 1914 and the 1950s. The major changes were in ownership.
During the First World War all mainline railways came under Government control and the advantages of some amalgamation became obvious. An Act was passed in 1921 creating four large companies to absorb most of the country's railways from 1 January 1923. Two of these companies shared Scotland's railways: the London, Midland & Scottish (LMSR) absorbed the CR and GSWR ending their traditional rivalry; and the London & North Eastern (LNER) took over the NBR. The LMSR and LNER remained rivals for both suburban and mainline services. Glasgow Corporation took over the Glasgow District Subway in 1922 and electrified it in 1933-5. On both suburban and main lines the mainline companies introduced improved locomotives and rolling stock.
After the Second World War the Labour Government nationalised the railways with effect from 1 January 1948 as British Railways. It, too, built new locomotives and rolling stock, but did not alter services much. In the mid-1950s, however, a modernisation programme was started with diesel locomotives and railcars replacing steam-operated services and some electrification that included the Glasgow suburban services. The first phase, on the north side of the city, was begun in the 1950s, opening in 1960.