Network Rail engineers have finished renewing track through a narrow Victorian railway tunnel on the West Coast Main Line.

It describes the work as “complex” and “trickily tight”, and promises that its completion will improve West Coast Main Line journeys for passengers and freight.

The work involved removing four hundred metres of railway line through Northchurch Tunnel between Berkhamsted and Tring in Hertfordshire.

Network Rail carried out the work as part of the Central Rail Systems Alliance (CRSA), which is a partnership with Balfour Beatty, Atkins and TSO. They began the work last Tuesday (New Year’s Eve) and finished on Saturday (4 January).

The work site encompasses three tunnels. Between them, they take the West Coast Main Line’s four tracks underground. The two fast lines share a tunnel, while the two slow lines have a tunnel each.

The oldest of the tunnels was built in 1836. Workers needed to replace track in one of the slow tunnels, but could not use traditional techniques in such a tight space. This made the renewal logistically “tricky”.

Moreover, this is a section of one of the busiest mixed-use passenger and freight rail routes in Europe. Network Rail had to close both slow lines to trains while carrying out the work. All trains used the fast lines instead. Because of this, operators had to run a reduced service.

Workers carried out the upgrade in distinct stages. This enabled them to remove the old equipment and material before bringing the new tracks in.

The work involved:

• installing 672 new sleepers on 24 track panels
• removing 1,860 tonnes of old spoil from the tunnel
• laying 2,200 tonnes of new ballast
• using six engineering trains
• installing 430 metres of steel rail
• staff working a total of 2,440 hours.

Today (Monday, 6 January), Network Rail is conveying its thanks to passengers for showing patience during the period that their journeys were disrupted.

“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.”

Neil O’Toole, Network Rail Capital Delivery senior programme manager