A417 Missing Link project starts build of new underbridge
Concrete beams are being lifted into place for a new underbridge
The A417 Missing Link project has hit its next major milestone – building a new underbridge that will form part of a major new junction.
National Highways, along with contractor Kier, has this week started lifting 53 20-tonne pre-stressed concrete beams into place that carry nine lanes of traffic over the new Shab Valley junction.
Once lifted into place, the beams will form an underbridge 20 metres wide and 62 metres long, providing access to nearby kennels, residents and factories when switched from existing to new road through Shab underbridge.
It will also allow traffic from the A436 Seven Spring and the B4070 Birdlip to easily enter and exit the new A417 without disrupting the flow of traffic.
Concrete beams were chosen over steel beams as a construction solution due to their performance and practicality.
The reduced weight of concrete enables construction using a smaller crane which simplifies logistics, manages health and safety risks, and lowers overall construction costs when compared with a steel girder construction.
Longer term, it also reduces maintenance requirements by utilising an integral construction and concrete specification tailored to local environmental conditions.
Celine Acard, National Highways’ Senior Project Manager for the A417 Missing Link, said: “We’re really proud of the progress we’re making on this major upgrade of the A417, and work taking shape on the new Shab Valley junction is a testament to our pace and efficiency on the scheme.
“We’re keen to make sure that this scheme benefits the local community as well as motorists and the new junction will ensure easy access to and from the main carriageway whilst minimising disruption.
Colin Fowler, Head of Highways at Tony Gee who designed the bridge, added: “The philosophy behind the junction design was to work with the natural topography, setting the underpass within the Shab Valley.
“This will reduce the elevation of the A417 carried by the bridge, minimising visual and noise impact of the new road. A bridge set into the landscape in this way required a structural solution which would last.
“The integral bridge with precast prestressed concrete beam deck will require only minimal maintenance through its’ lifetime and importantly will not require closure of the A417 above to do it.”
Following the beams being lifted into place, the new nine lanes of carriageway, five of which make up the main A417, will be built on top, along with entry and exit slip roads.
The underbridge is a major milestone for the scheme, with its construction allowing National Highways to look towards a traffic switch from the existing A417 and onto the new stretch of road in early 2026.