Manchester, South Junction and Altrincham Railway

In the early part of the 20th century, the MSJ&AR steam trains came under increasing competition from electric tramways, which by that time ran the whole way from Manchester to Altrincham and closely followed the route of the railway.

Various electrification proposals were studied to counter this threat, although it was only after the 1923 Grouping that concrete action was taken. Following Grouping, ownership and management of the line was taken over by an MSJ&AR Committee, representing both the London, Midland and Scottish Railway (LMS) and the London and North Eastern Railway (LNER). The LNER was particularly interested in the electrification of mainline railways and in 1928 a government report had recommended 1500 V DC overhead as the national standard system.

Despite the LNER's enthusiasm for electric traction, the LMS was the company responsible for installing most of the new electrification infrastructure on the line, while 22 new 3-car electric multiple units (EMUs) were built for the line by Metropolitan-Cammell to an LMS design. The new rolling stock was of wooden frame construction and a conservative design, with individual compartments throughout (without corridors) and offering both first- and third-class accommodation. The electric multiple units were all based at a new depot, located just south of Altrincham and Bowdon station on the site of the original MSJ&AR Bowdon terminus.

The new trains began test runs in 1930 and on 11 May 1931 the London Road to Altrincham local service became fully electric. Coinciding with the electric service, new suburban stations were opened at Dane Road and Navigation Road. The station formerly called Old Trafford Cricket Ground (which had opened only for matches at the nearby Lancashire County Cricket Club, or Manchester United football ground) was opened full-time and renamed Warwick Road.

The Altrincham Electrics provided a faster, more frequent service than the steam trains they had replaced, and resulted in an 89% increase in patronage on the line within the first five years. The new electric service also stimulated further suburban housing development close to the line, and provided an early example of today's marketing taglines when the railway's publicists dubbed the initials MSJ&AR as Many Short Journeys and Absolute Reliability.

As well as local trains, the Altrincham Electrics also provided express services at certain times of day, making use of a four-track section of line between Sale and Old Trafford. Some of the all-station electric trains ran only between Manchester and Sale, while steam-hauled passenger and goods trains also used the MSJ&AR to travel to destinations beyond the boundaries of electrification at either end of the line. Passenger trains ran from the ex-Cheshire Lines Committee (CLC) line from Chester Northgate to Manchester Central, diverging from the MSJ&AR at Cornbrook Junction. There was also a local service from the ex-LNWR line from Warrington Arpley, via Lymm which terminated at Manchester London Road.

The success of the MSJ&AR and the reliability of the 1500 V DC distribution encouraged the LNER to pursue further electrification. These projects were disrupted and delayed by World War II, but in 1954 the first mainline electric railway in northern Britain was completed from Sheffield Victoria to Manchester London Road via the Woodhead route, using 1500 V DC overhead. This line approached London Road from the east and although it was equipped with the same electrification system as the MSJ&AR and had its own fleet of 1500 V DC suburban EMUs (later to be classified as Class 506), the two electric lines were never connected at London Road and the two types of EMU never ventured onto each other's territory.

In common with most railway routes, passenger traffic on the MSJ&AR declined significantly in the 1960s as travel patterns changed and more people had access to private cars. As a result, the Altrincham Electric express services were withdrawn, along some of the rolling stock and many of the goods trains using the route. The quadruple section of MSJ&AR track was reduced to conventional double track in 1963 and Manchester Central station closed on 5 May 1969, with trains from the ex-CLC Chester and Warrington lines being diverted to terminate at Oxford Road.