The innovation – believed to be a world first – has avoid the need to demolish a Victorian railway bridge by making the bridge usable by new electric trains. Use of the technology saved an estimated US$56 million in the cost of rebuilding the structure.

Network Rail now investigating deploying the technology nationally, backed by the data it has gathered since completion of the Intersection Bridge in Wales.

Electrification of the railway running between London and Cardiff was completed just over a year ago. As diesel trains were replaced with electric ones, Network Rail engineers were tasked with the job of installing overhead wires and cables to run them. Most routes were designed during Victorian times and this often means that large structures like bridges need to be reconstructed before electrification is installed.

Network Rail engineering expert Richard Stainton said: "Intersection Bridge – situated in the centre of Cardiff, on the Wales route – is a prime example. The structure is too low to safely fit all the kit required.

"Ordinarily, this would force Network Rail to demolish it and rebuild it at a greater height to keep electric trains a safe distance away from the bridge as they pass under, and stop them from electrifying the bridge itself, or anything on it."

In this case however, Network Rail coated the underside of the bridge with electric-resistant paint. This is a new technology that has been developed with the University of Southampton.

Electric-resistant paint on Intersection Bridge in Cardiff

It was used alongside specially developed lineside kit, including surge arresters and insulated bridge arms, to insulate the bridge from electricity and make it safe for electric trains to pass under.

In what Network Rail said is a world first, the electric resistant paint was combined with voltage-controlled clearance (VCC), which allowed the electrical clearance gap to be reduced by 20mm from the overhead line equipment (OLE) to the bridge, and 70mm from the OLE to the train roofs.

This meant around US$56 million of savings as the bridge did not need to be knocked down to start from scratch.

Peter Smith-Jaynes, regional asset manager, electrification, Wales & Western, said: "It's a really complex situation at Cardiff Intersection Bridge. It's a very busy rail-over-rail bridge, with a canal underneath that, and it's surrounded by high-rise buildings. Just accessing the bridge would have been difficult but knocking it down and rebuilding it would have been nearly impossible. We had to find another solution.”

Stainton said: "Typically, a third of electrification project expenditure is on reconstruction and modifying of civils structures – tunnels, bridges and stations – to allow the installation OLE with the necessary clearances.

"This solution will create enormous efficiencies; allowing future electrification projects to be installed and energised without multi-million-pound expenditure – potentially saving the tax-payers as much as £100 million [US$140 million].

"It will also significantly reduce the number of rail closures – for access – lowering the disruption to passengers, road networks and railway neighbours."

Smith-Jaynes added: "As a Welshman, I'm proud we've been able to trial this innovative, new technology here in Cardiff, and can look back on it knowing we've made a difference, potentially saving the taxpayer millions as we roll it out on future electrification projects elsewhere."