The South Rail Systems Alliance (SRSA) has completed a major programme of infrastructure upgrades on the West Anglia main line.

Appointed in September 2023, the SRSA, comprising Colas Rail UK, Network Rail, and AECOM, delivered a package of works between Shepreth and Cambridge. This multidisciplinary project was carried out in collaboration with station contractor Murphy and signalling partner Alstom.

Key upgrades included:

• Renewal of 5.7km of track and the realignment of 1.4km to accommodate the station's new four-platform configuration

• Installation of eight new track switches

• Upgrades to the overhead line electrification system, including 110 new foundations, 79 new structures, and nearly 10km of new wiring

• Installation of eight new signals

• Remodelling of Shepreth branch junction to support higher train speeds

• Modernisation of supporting systems such as communications, telecoms, and power supply infrastructure


Construction milestones were reached through carefully coordinated blockades and weekend works, including a significant blockade over Christmas 2023 to divert the main lines and enable platform construction.

Further upgrades took place during key weekends in May and June 2024, when new switches and crossings were installed and overhead lines modified to maintain power to the realigned tracks.

In Christmas 2024, SRSA successfully completed the remodelling of Shepreth branch junction, extending the junction and softening the curve radius. This enhancement will allow trains to pass through the junction at 50mph—up from the current 30mph—once signalling upgrades are completed in late 2025.

As part of this work, two new tracks were also connected to their final alignments through Cambridge South, completing its transformation into a four-track, four-platform station.

The SRSA delivered more than 124,000 staff hours across 10,000 shifts without any major incidents, reflecting a strong focus on safety and innovation, including the use of geofencing and worker tagging technologies.

Beyond the rail infrastructure, SRSA contributed to local community initiatives in partnership with the local authority's environmental team, undertaking volunteer activities such as litter removal, vegetation management, and new fencing installation at a nearby nature reserve.

With the rail systems phase now complete, contractor Murphy will continue the station’s fit-out through to autumn 2025. Network Rail and Alstom are also progressing with the next stage of the signalling renewal programme, which will enable the new Cambridge South station to open in early 2026.