Werrington Dive Under

Werrington Dive Under (also known as the Werrington Grade Separation) is a replacement dual track grade separated railway junction at Werrington Junction, north of railway station in Cambridgeshire, England. The junction leads to the Great Northern/Great Eastern Joint line (GN/GE) which goes through to and beyond. Completed and opened in December 2021, the dive under allows trains on the west side of the East Coast Main Line (ECML) to access the GN/GE line without conflicting with the faster passenger services on the ECML.

The dive under was constructed by a 'jacked deck' on slide paths installed in access tunnels. The curved 'jack deck', pushed into place beneath the main running lines, will be the first use of such a structure in the United Kingdom. The installation uses a patented method of construction.

Original junction

When the line closed between and Spalding in 1982, freight traffic, instead of cutting across the western edge of the Fens, was diverted through Peterborough station. Trains therefore had to use Werrington Junction, located north of Peterborough railway station, for access to/from the GN/GE line. In order to use the junction trains have to cross the lines used by the fast ECML passenger services on the level and, in the case of trains to Spalding, also use the Up Fast line for three miles between Peterborough station and the junction. This can cause delay to fast passenger trains.

Railtrack, Network Rail's predecessor, recognised that the ECML was congested and so upgraded the GN/GE line to accommodate the heavy container trains to and from the east coast ports. However Werrington Junction was still a significant bottleneck.

The dive-under

In 2016 Network Rail submitted a Transport and Works Act Order (TWAO) to the Secretary of State for Transport to build either a flyover or a dive-under to avoid the fast lines north of Peterborough and allow passenger and freight trains to access all lines without affecting other faster services. In summer 2018 Chris Grayling approved the order after a public inquiry favoured the dive-under option in preference to the flyover. Initially costings were estimated to be in the region of £100 million, but the agreed cost on approval was £200 million.

The project saw the construction of of new line which runs underneath the fast lines, culverting works on Marholm Brook, and the movement of the lines westwards over the culverted brook. This means that trains for the GN/GE line no longer need to cross the fast lines on the level, nor use the Up Fast line between Peterborough station and the junction. The project, coupled with other ECML improvement schemes (such as the four-tracking from to Woodwalton), improved capacity on the line through Peterborough by 33%, according to Network Rail. This equates to two extra train paths an hour in 2021, when the work was completed. This will, in turn, cut 21 minutes off the fastest to service, 13 minutes off the fastest King's Cross to service, and it will also see an increase of 1,050 'Intercity' possible seats per hour on express trains through Peterborough.

The Spalding and Peterborough Transport Forum claimed that increasing the number of freight trains operating through Spalding would cause the level crossing barriers in the town to be down for 24 minutes of every hour. The Campaign for Better Transport praised the works and stated

The construction will involve use of the UK's first curved box jack, which will consist of ten sections joined together, creating a curved box. The contractors expect to remove of earth and the box will weigh .

The junctions at the north and south ends were connected in November 2021, as was the signalling. However, regulatory approval will mean a projected opening date in December 2021. Provision has been made for future overhead electrification works if necessary.

See also

* Hitchin Flyover - a flyover at Hitchin to alleviate traffic problems in accessing the Cambridge line north of Hitchin
* Nuneaton North Chord - a flyover on the West Coast Main Line at Nuneaton constructed for similar reasons

Video of tunnel box being pushed into place

References

External links

Network Rail news release with computer generated video of the new lineTWAO government documentsVideo of the box being pushed under the ECML, hosted on BBC News

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Rail junctions in England
Rail transport in Cambridgeshire
Tunnels in Cambridgeshire
Peterborough
East Coast Main Line