World War II had seriously disrupted Scotland's railways due to the LMS and LNER rolling stock in Scotland being transferred to the major cities in Northern England in order to replace what had been destroyed by German air-raids. At the time, the Government believed that only state intervention could provide the necessary re-supplying of rolling stock and save several unprofitable routes from closure.
Following the election of the Labour government in 1945, the railways were nationalised on 1 January 1948 under the terms of the Transport Act 1947. Through the creation of the Scottish Region of British Railways, all Scotland's railways were brought under a unified system of management for the first time.
The major change to passenger services became apparent in the late 1950s, with the introduction of diesel locomotives, diesel multiple units and - most of all - the electrification of the Glasgow area local services and the introduction of the "Blue trains", as well as the final withdrawal of steam locomotives in 1967.
During the mid 1960s many routes were closed under the "Beeching Axe", plus some after the resignation of Dr Richard Beeching - most notoriously the Waverley Line from Edinburgh to Carlisle.
In 1974 cross-border electric Inter-City services from Glasgow Central to London Euston commenced, with the completion of the West Coast Main Line electrification project. In 1979 the Argyle Line project saw the reopening and electrification of the railway line through Glasgow Central Low Level station. The Glasgow Central to Ayr line was electrified in 1986. The one closure of this period was the Kilmacolm line in 1983.
The Edinburgh Waverley - Glasgow Queen Street service was operated by diesel multiple units from the late 1950s until 1970, when "push-pull" trains of Mark 2 carriages with a Class 27 diesel locomotive at each end were introduced. These were replaced by Class 47 locomotives and Mark 3 carriages in 1979. These were in turn replaced by Class 156 then Class 158 units in the early 1990s.