Bushey power supply upgrade to West Coast Main Line

Project summary

This project involved the procurement, construction, testing and commissioning required to implement a 25-0-25 kV auto-transformer system between Bourne End and North Wembley, as well as modification of Acton Lane feeder station to improve the resilience of traction power supply to the West Coast Main Line (WCML). This required multiple access possessions to deliver the work, ultimately benefiting both passengers and freight customers.

During a 6-day shutdown of the WCML, engineers conducted surveys and upgrade works. RSK Group companies Octavius Infrastructure and Global Rail Construction delivered the work over the Easter 2026 period for Network Rail.

The background

The Bushey electrical upgrade project aimed to deliver auto-transformers to the electric lines between Bourne End in Buckinghamshire and North Wembley in London, while introducing broader infrastructure upgrades to enhance resilience through to Euston in central London on the WCML. The project also aimed to increase capacity for the line to facilitate growth and mitigate congestion.

This involved removing a series of oil-filled transformers and updating with an auto-transformer system (+/- 25 kV 50 kV system), which reduces voltage drop, extends range and minimises electromagnetic interference. The work included creating three new substations and refurbishing two existing units. The first phase of the work converted the remaining areas of legacy power supply systems to the new system, modified the feeder busbar at Acton Lane, introduced a back-up power supply and brought assets up to modern safety standards.

Work originally began on the project in autumn 2025, but the Easter bank holiday 2026 was identified as a suitable 6-day window for which the required line shutdown could take place.

Multidisciplinary approach/strategy

RSK Group company Octavius Infrastructure led the project for Network Rail and closely collaborated with sister RSK Group company Global Rail Construction. This collaborative effort contributed to the project’s success where, from the outset, both teams aligned on shared objectives, communication protocols and a unified approach to risk and programme management. This created a seamless working environment where expertise, resources and decision‑making flowed naturally across organisational boundaries. The ability to integrate planning, coordinate logistics and respond collectively to emerging challenges ensured that the project remained on track without compromising quality or efficiency.

Both companies upheld a joint commitment to safety, maintaining the same high standards and reinforcing these through consistent briefings, shared learning and a proactive safety culture that encouraged everyone on-site to speak up and take ownership. This unified approach resulted in the safe delivery of all works, with no major incidents and a strong record of compliance throughout the project. The partnership demonstrated how two businesses from the same group can operate as one cohesive team, delivering outcomes through trust, alignment and shared values.

The challenges

Upgrading the WCML’s power supply at Bushey presented a long-standing challenge. Access to the line, where local commuter services run on slow lines alongside a busy section of the main line, had been the principal challenge. To deliver the upgrades safely, the line needed to be closed to traffic and the overhead lines turned off, which is not possible at any given time due to the frequency of use.

Delivery of the work also had to account for the unusual configuration at Bushey, where the AC overhead lines are positioned directly adjacent to the DC conductor rails on the slow lines. The WCML uses overhead AC (25 kV) for express trains, while local services, particularly on the slow lines, historically operated on DC third rail.

Due to the frequency of traffic, planning and execution of the works were carried out to extremely short timescales, taking just 12 weeks of planning and 6 days on-site when the lines were closed.

The solutions

During the project mobilisation period, the teams attended interface meetings with the project discipline leads to review the redline drawings and verify the infrastructure that had been installed to date. This process enabled the team to effectively plan the remaining works while integrating activities with other contractors contributing to the project.

The interface reviews also identified areas where people and plant interactions presented potential operational and safety challenges. By identifying these interfaces early, the team was able to implement revised sequencing and safe-working arrangements to minimise works taking place around moving plant. Higher-risk activities were rescheduled to later stages of the possession, when plant movements had reduced, while still maintaining the planned outputs and overall programme milestones.

This collaborative planning approach improved coordination across all disciplines, enhanced safety within the work site and ensured the efficient delivery of the works within the restricted possession window.

The impact

As a result of coordinated efforts, the closure of the line at Bushey enabled the safe and successful completion of the electrical works, providing long-term benefits to both the rail sector and the wider community. The power supply upgrades will improve the resilience, reliability and capacity of the WCML, supporting increased service performance and future growth in passenger and freight demand. Enhanced power infrastructure will also facilitate the continued modernisation and decarbonisation of the railway network by supporting more efficient electric train operations.

For passengers and local communities, the project contributes to a more reliable railway with fewer delays and improved service continuity. In the wider sector, the collaborative planning methods, interface management processes and innovative delivery techniques adopted during the works provide a strong example of how complex upgrades can be delivered safely and efficiently within highly constrained operational environments. These lessons and best practices can be applied to future rail infrastructure projects across the industry.