‘Box structure’ flyover saves £70m and six months for East West Rail: Bletchley flyover box structure drone shot October 2021

Tuesday 16 Nov 2021

‘Box structure’ flyover saves £70m and six months for East West Rail

Region & Route:
North West & Central
| North West & Central: Central

Engineers have saved £70m of taxpayers’ money by using creative new methods to build a railway flyover as part of the East West Rail project.

Network Rail and the East West Rail Alliance are restoring the Oxford-to-Cambridge line by removing and replacing a flyover which crosses the busy West Coast main line at Bletchley - all while keeping trains and passengers moving safely.

The new structure, on the line between Bicester and Bletchley, is being built to last 120 years with minimal future maintenance required.

Instead of replacing the old flyover like-for-like - which would involve closing the West Coast main line below to build five supporting columns in between the tracks - East West Rail project engineers have used modern methods of construction to build a protective ‘box structure.’

It acts very much like a rectangular railway tunnel, removing the need for separate supporting columns and providing a platform for the flyover to sit on.

This means the West Coast main line - which is one of the busiest mixed-use passenger and freight railway routes in Europe - doesn’t have to be closed during the flyover replacement taking place above as the box structure provides a protective, physical barrier.

This keeps both passenger and freight trains safe below and the workforce safe above.

Mark Cuzner, East West Rail Alliance project director, said: “By working smarter we’ve been able to speed-up the project by around six months. At the start of the project, we built a protective wall next to the West Coast main line so we could safely build the box structure during the day when the railway is open, instead of working piecemeal at night-time when the railway is closed.

“Most of the components for both the box structure, and the flyover, arrived pre-built and were simply assembled on site, like a model kit or set of Duplo bricks. The simplicity of construction meant we could safely reduce the workforce onsite by 60%, cut the previously-forecast cost by £70m and get the job done six months quicker than planned.”

Simon Blanchflower CBE,  East West Rail Company chief executive officer, said: “The transformation of the iconic Bletchley flyover has really brought the East West Rail project to life and brings communities from Oxford to Cambridge ever closer to a new, sustainable transport link across the region”

Key figures from this innovative construction technique include:

  • £70m saved by reducing the need to close the railway
  • Modern methods of construction speeds-up project by six months
  • 70% of components arrived pre-built and were simply assembled on site
  • Simplicity of construction meant onsite workforce could be reduced by 60%
  • New flyover will last 120 years (previous one lasted only 60 years)

In the coming months track will start to be laid over the new structure.

It replaces a 1960s-built concrete railway flyover which wasn't suitable to carry the new East West railway.

The huge demolition project on the old structure took place throughout 2020 and involved some of the UK's largest cranes.

For more information on the East West Rail project visit: www.networkrail.co.uk/east-west-rail/ 

Notes to Editors

  • Bletchley flyover’ was built in the early 1960s and allows trains travelling from West to East to cross over the West Coast main line.  As part of East West Rail the flyover is being rebuilt to modern day standards making sure the structure can accommodate trains for another 120 years. It is an essential part of the project which will see the first direct rail link between Oxford, Bicester, Bletchley and Milton Keynes in more than 50 years.
  • Sections of the flyover were demolished in 2020 and the reconstruction of the new structure is now complete ready for the next stage of the project which will install the track and signalling.
  • The work to dismantle and rebuild the structure over the West Coast Main Line, one of Europe’s busiest railway lines, was innovatively planned, designed and carried out with minimal disruption to passengers and train services.
  • In total 15 of the existing flyover spans – each weighing circa 300 tonnes and 9 piers were removed, which involved mobilising three of Europe’s largest mobile cranes.
  • The rebuild included an innovative design to install the flyovers support structure using 138  oncrete shell abutments and culminated in the installation of 103, 40 tonne precast concrete beams required to construct the new box bridge over the WCML during the early May bank holiday in 2021. During this possession the project team also dismantled and reassembled the complex web of 25,000-volt overhead electric cables underneath the new flyover.
  • Waste material from the dismantled spans and piers was recycled and reused in other infrastructure elements along the Bicester-Bletchley route, creating additional environmental and efficiency benefits.
  • East West Rail is planned to be delivered in three Connection Stages:
  1. Connection Stage One: Oxford to Bletchley and Milton Keynes
  2. Connection Stage Two: Oxford to Bedford
  3. Connection Stage Three: Oxford to Cambridge
  • Network Rail was responsible for developing the first part of the East West Rail, connecting Oxford with Bicester, and is a partner in a construction alliance to deliver Connection Stage 1 of the project, where East West Railway Company (EWR Co) and Network Rail are acting as the Department for Transport’s joint sponsors.
  • The East West Rail Alliance is delivering the Connection Stage One phase of the scheme and consists of Network Rail, Atkins, Laing O’Rourke and VolkerRail.
  • EWR Co is now developing the route to enable services to run to Cambridge via Bedford and plans to seek statutory powers under the Planning Act 2008, following a period of extensive consultation.

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