|Location Map ( geo)|
|Caernarfonshire • Anglesey|
(Rebuilt early 1970s)
|Crossings related to the A55|
|Chester Bypass Bridge • Conwy Tunnel • Holyhead - Dublin ferry • Holyhead - Dun Laoghaire ferry • Pen-y-Clip Tunnels • Penmaenbach Tunnels • St Asaph Bypass Bridge • Stanley Embankment|
Britannia Bridge was built by Robert Stephenson to carry the Chester and Holyhead Railway across the Menai Strait. It is situated a mile west of Telford's Menai Suspension Bridge and was begun in 1846 and opened in 1850. The original structure was of a type then known as a tubular bridge, which would today be called a box-girder bridge: two rectangular-section wrought iron tubes supported by a series of tall masonry towers, with the rail tracks inside the tubes. This was similar to Stephenson's rail bridge at Conwy but bigger. An alternative proposal involving arched construction was ruled out because of the need to maintain clearance for tall ships below. The strait itself is crossed in two spans, with a central tower founded on the Britannia Rock, from which the bridge gets its name.
The tubes were severely damaged in a fire in 1970 but the towers remained. The bridge was re-built with steel truss arches supporting a new reinforced concrete deck, carrying a single rail track alongside a maintenance access road. The first train after reconstruction crossed in 1972. Work started in 1977 to add a road deck above the railway; this opened in 1980 to carry the A5 which, following completion of the new dual carriageway across Anglesey, was re-designated as A55 in 2001.
The road deck is of WS2 standard and is the only non-dualled section of the A55. In 2007, a public consultation was held on options for dualling the crossing, of which nothing came. In 2016 a new consultation was started (source: BBC News).
Bizarrely, this is not the only road-rail bridge named Britannia Bridge in Caernarfonshire: see Britannia Bridge (Porthmadog).