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Infrastructure insights: bridges, tunnels and viaducts

We’re responsible for the 30,000 bridges, tunnels and viaducts on Britain’s rail network. 

Our regular maintenance projects often include essential works on some of these structures.

These included a bridge in the Manea area between Ely and Peterborough over Christmas. We replaced timbers as part of a project to reverse years of weather-related erosion.

In Newcastlewe carried out waybeam renewal on the listed King Edward Bridge. We replaced the timber beams supporting the track as part of a 12-year renewals programme.

Preserving the past… for the railway of the future

Many of our bridges, tunnels and viaducts date from the Victorian era; looking after some of the country’s most celebrated structures is a privilege and a challenge.

Maintenance is important but that’s just one part of our work. Railway passenger numbers have doubled in the past 20 years so we have to modernise and adapt our infrastructure as part of our Railway Upgrade Plan.

Our asset teams check whether they can accommodate new electric trains and those carrying freight. They also carry out repairs as required.


Technological advances are improving the way we work in tunnels and on other structures. In September 2018, Network Rail Scotland used a track-based three-dimensional scanner for the first time to precisely model the railway infrastructure ahead of the arrival of new, state of the art trains.

Ensuring new trains fit on existing lines has never been more crucial or time critical. The Trimble GEDOScan system – operated by Network Rail’s team of absolute track geometry (ATG) engineers – collected detailed information about the track and surrounding features such as bridges, parapets, and platforms. It can quickly gather precise, high-resolution data for use in track clearance assessments on our structures.

3D technology gathers data in one of our tunnels

Innovation: avoiding bridge reconstruction

Bridge jacking at Tennison Road bridge in Croydon

Overhead line equipment has to be installed to electrify the railway. This usually means there needs to be a greater distance between the railway and any bridges above, so the overhead equipment fits beneath the bridge. Typically, the methods to create this extra headroom are either lowering the track or demolishing the bridge arch and replacing it with a precast concrete unit.

Where possible, we avoid reconstructing bridges because it’s usually the most expensive option and can disrupt the road and rail network. It can be the best choice if a bridge is in poor condition but technical alternatives can provide solutions that avoid this costly reconstruction.

The Rail Safety and Standards Board (RSSB) teamed up with Network Rail and the Department for Transport to try to find potential innovative solutions.

RSSB, Network Rail and the Department for Transport launched the Avoidance of Bridge Reconstruction competition in February 2014 as a co-funded innovation-based project. Its aim was to find solutions to increase the clearance beneath masonry arch bridges without the need to rebuild these structures.

The competition was open to all industry. Of 11 submissions, nine were funded through phase one (feasibility study) and four won funding for the phase two full-scale demonstrator project off the live rail network. This stage was needed to confirm that any technical design assumptions were valid and to prove the methods and equipment worked correctly.

ElevArch jacking technique

One of the proposals that made it to this final stage was from Freyssinet and Bill Harvey Associates, who developed the bridge-jacking solution ElevArch, which now has UK and international patents and has won numerous industry awards.

The demonstrator took place in autumn 2016 on a bridge at Moco Farm near Winslow, Buckinghamshire. The segmental arch design dates from 1850 on the mothballed Bicester-Bletchley line, which will be part of East West Rail phase two. The bridge is 4.3m wide with a 10.1m span, and was designed by renowned civil and mechanical engineer Robert Stephenson.

Bridge-jacking is a technique usually used for bridges with a flat-deck span made of steel or concrete, so this was the first time in the world it had been attempted on a masonry arch bridge.

The benefits of ElevArch include reduced costs, shorter and fewer possessions, and reduced environmental impact. The structure is also retained, improving heritage value.

Watch the video below to find out more about the ElevArch technique:

Case study: Ordsall Chord bridge replacement 

Manchester’s Ordsall Chord is one of our most high-profile projects. It’s the the flagship scheme in the Great North Rail Project, linking Manchester’s three main railway stations – Piccadilly, Oxford Road and Victoria –  and helping to transform travel in the  North of England.

In 2017, it won the prestigious Major Project award at the Rail Industry Innovation Awards.

The chord will reduce journey times and enable faster, more frequent services to run through the city to and from other major economic centres in the north by reducing railway congestion by 25% in the railway hub of Manchester.

It was built as part of an alliance between Network Rail, Skanska BAM, Amey Sersa and Siemens:

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