The route is recognised as a significant bottleneck, magnified further by the opening of the Ordsall Chord in 2017 and timetable change in May 2018 which increased the number of services through Manchester city centre from 12 to 15 trains per hour.
[3] This uplift in services had a detrimental impact on punctuality and reliability, ultimately playing a major factor in the failure of the Arriva Rail North franchise in 2020.
The corridor is on a 1.5-mile-long (2.4 km) viaduct,[5] built by the Manchester, South Junction and Altrincham Railway in the late 1840s as a near continuous series of red brick vaulted arches, interspersed with iron or steel bridges.
[10] In an attempt to obligate the Department for Transport to provide funding for the Oxford Road upgrade to improve punctuality, Network Rail declared the Castlefield corridor 'congested' in September 2019.
However, the phased recovery process enabled both Northern and TransPennine Express to achieve a higher percentage of reliability and service than in the period immediately before the lockdown.