
Small Dean Viaduct
The striking 345 metre long Small Dean Viaduct just south of Wendover will carry the HS2 line across the A413, Small Dean Lane and the Chilterns rail line. After crossing the viaduct, northbound trains will pass the town of Wendover in a short tunnel designed to reduce its environmental impact.
A shared foot and cycle path will also be delivered by HS2 alongside the main road as it passes under the viaduct between the A413 London Road roundabout and the houses near Rocky Lane. This will eventually form part of the Misbourne Greenway project designed to link Wendover with Great Missenden.
Viaduct construction
Viaduct design
Designed to be seen from close-up the viaduct is one of only two places in the Chilterns where the HS2 route will be above ground level, with the underside of the viaduct just 6 metres above the road, supported by five ‘Y’ shaped piers.
The viaduct’s beams will be made from weathering steel, which naturally ages to a characteristically dark russet finish to echo the natural tones of the surrounding landscape. The pale concrete parapet and noise barrier along the top of the viaduct is designed to throw the dark steel into shadow, helping to give the appearance of a lighter and thinner structure. The piers are also designed to be as slender as possible.
Structurally, the viaduct beams will use an innovative ‘double composite’ approach, like the nearby Wendover Dean Viaduct. This involves two steel beams sandwiched between two layers of reinforced concrete to create a super strong but light weight span, dramatically cutting the amount of embedded carbon in the structure. The side of the beams will also have deck stiffeners to help manage the structural forces while allowing for a lighter weight beam.

Slide 1 of 5: HS2 Small Dean Viaduct pier and girder alongside the A413.

Slide 2 of 5: HS2 Small Dean Viaduct close up of strengtheners above a pier.

Slide 3 of 5: HS2 Small Dean Viaduct A413 looking south.

Slide 4 of 5: HS2 Small Dean Viaduct from above crossing A413 and Chiltern rail line.

Slide 5 of 5: HS2 Small Dean Viaduct A413 looking north.
Key facts
- Length: 345m
- Height: 6m
- Number of piers: 5
- Construction approach: ‘Double composite’ steel beams for strong but lightweight spans.
Keeping you informed

Stay informed about the works
Find information about HS2 works and activities taking place in your area.

Managing impacts of construction
Find out information about how we manage construction impacts.

Construction look-ahead
Read our three-month lookahead for associated work in Buckinghamshire and Oxfordshire.

Find out what HS2 means for Buckinghamshire and Oxfordshire
This section provides you with information about HS2 works and developments in your area.
Find out more