Engineers have completed a complex track renewal through a narrow Victorian railway tunnel to improve West Coast Main Line journeys for passengers and freight.

Network Rail and its contractors* started work on New Year’s Eve to replace 400 metres of railway line through Northchurch Tunnel between Berkhamsted and Tring. Three tunnels take the West Coast Main Line’s four tracks underground on this section of one of Europe’s busiest mixed-use passenger and freight rail routes.

At this location the two fast lines share a tunnel, and the slow lines have one each – the oldest of which was built in 1836. As track needing replacing through one of the slow tunnels, it made the renewal logistically tricky as traditional techniques were not an option in such a tight space.

Instead work had to be done in specific stages** to get all the old equipment and material out before the new railway could go back in. In total the work between 31 December and 4 January saw:

  • 672 new sleepers installed on 24 track panels
  • 1,860 tonnes of old spoil removed from the tunnel
  • 2,200 tonnes of new track foundation stone (ballast) laid
  • Six engineering trains used
  • 430 metres of steel rail installed
  • Staff working a total of 2,440 hours to get the job done

Because of the complexity of the essential upgrade, both slow lines were closed to trains throughout the project, with all trains using the fast lines instead.

All lines reopened on Saturday 4 January, and on Monday, January 6, passengers are being thanked for their patience as trains ran at a reduced timetable during the improvement work. Neil O’Toole, Network Rail Capital Delivery senior programme manager, said: “We know there’s never an ideal time to close a section of railway, so I’d like to thank passengers whose journeys may have taken a little longer while we made these important improvements through Northchurch Tunnel.

“This track renewal was a bit of a Rubik’s cube to complete as we had to do each stage in a predefined sequence and the job took nearly three years to plan. It was our priority to make it work and get the railway reopened on time.

“From today passengers will have a much smoother ride and fewer delays caused by further maintenance now we’ve brought the track here bang up to date.” This work through the 189-year-old tunnel has been completed in the Railway’s 200th Anniversary year.

Railway 200 marks the bi-centenary of the invention of the first passenger railway between Darlington and Stockton in September 1825. 

NB: *The work was delivered on behalf of Network Rail by the Central Rail Systems Alliance (CRSA), which is a partnership of Network Rail, Balfour Beatty, Atkins and TSO.

**The process of the work was:

  • Track panels had to be carefully removed one by one
  • Then bulldozers pushed old ballast spoil out each end of the tunnel and taken away by engineering trains
  • A new ballast bed was then created and 60ft panels installed within the tunnel using a front loading (Kirow) crane.  
  • A special ballast dropping train then travelled over the temporary rails (slave rails) dropping ‘top ballast’ before rail-mounted machines were used to profile it
  • A specialist Tamper machine was then used to lift the track and shake the ballast below, so the track was in the correct position for trains.
  • The ‘60ft slave rails’ were then removed and replaced by longer continuous pieces of rail which have fewer welds giving a smoother ride for trains and need less future maintenance