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Track and infrastructure upgrades on the Great Western main line

Major infrastructure upgrades have been delivered to allow more trains to run more reliably. These include:


Stockley Bridge replacement works April 2014_136396

A flyover has been installed at the junction to Heathrow in west London to add capacity to this busy section of the railway. This flyover consists of a new bridge which carries the trains coming from Heathrow over the Great Western main line leading to a viaduct and two ramps to link in with the tracks heading into Paddington.

At 120m long, the 1,000-tonne bridge was the largest single-span rail bridge to have been installed anywhere to the west of London since the days of Brunel and the whole structure stretches to more than a mile in length. 

The flyover carries Elizabeth line and Heathrow Express services heading towards central London enabling them to join the Great Western Main Line without delaying or being delayed, by other trains using the route. The flyover came into service in January 2017.

The bridge has been named ‘Sams Bridge’, after Richard Sams who had been the project engineer on Stockley from its inception in 2011 and whose work on the project played a major part in ensuring its success. Richard sadly died suddenly in 2014 while on holiday in Mexico.


Contstruction of new diveunder at Acton_carousel_210013

A dive-under is an underpass which allows trains to pass under another railway track without being held up by trains on the above track. The dive-under at Acton has been constructed so that trains leaving the nearby freight yard do not delay passenger trains heading toward central London. 

Freight trains leave the yard by crossing the passenger tracks between Ealing Broadway and Acton Main Line stations. The new dive-under allows Paddington-bound passenger trains to pass under an existing freight train without being delayed, increasing capacity and reliability.

The excavation of the dive-under itself began in October 2013 following nearly two years of work to re-configure the freight yard, which involved moving the tracks in the yard eight metres to the north, line by line over many weekends, and then putting in a new junction. The dive-under came into service in January 2017.


Overhead power works near between Maidenhead and Slough_218136

The build of the Elizabeth line also included the electrification of the Great Western route between Stockley Flyover and Maidenhead, beyond which the task was picked up by Network Rail’s Great Western Mainline electrification team. 

This work involved the installation of 1,400 piles beside the tracks to provide foundations for the overhead line equipment and the erection of steel structures at approximately 50-metre intervals on both the main and relief lines to support the overhead wires. Vegetation also needed to be cleared along the trackside in order to provide a safe environment for the operation of the high voltage wires.

Installation competed in 2017 and the overhead lines have been supporting the Elizabeth line and Great Western Railway electric trains since.

Contact us

If you have queries about the work taking place please contact Network Rail, which is delivering the Crossrail upgrades: