Severn Barrage - Trans-barrage Transport Links

Trans-barrage Transport Links

It is possible that some types of barrage could be used for transport links between southern England and southern Wales, and more specifically the areas around Bristol and Cardiff. The east-west position of any future barrage will impact the utility of any transport links across it. Various proposals include a dual carriageway road giving a further crossing in addition to the Second Severn Crossing and the Severn Bridge. The road would have to be taken over the sea locks on a bridge at a height of the Bridge of the Americas (i.e. with a clearance of 61.3m) if the locks are Panamax-sized.

Some proposals also include a double track railway line across the barrage. A railway would have a longer approach up to a fixed bridge over the locks. The approach would be greatest for non-electrified heavy railway capable of taking freight, slightly less for non-electrified passenger line, and less still for electrified passenger line. There is no electrification presently in the Bristol or Cardiff areas, but this would change with the electrification of the Great Western Main Line. An alternative to a fixed bridge would be a swing bridge, though there is concern expressed at this reducing capacity through the locks and on the railway. However, two swing bridges, one at either end of the lock would mean that one bridge could be kept open to railway traffic at all times. The double track could be reduced to single track at this point without creating too much of a bottleneck, or if double track is required this could be worked around by grade separating the two lines and having double-decked bridges. The line could then be used to partially relieve the Severn Tunnel.

The option for a new fixed rail link has implications for several wider transport proposals. One of the proposed routes for an Irish Sea Tunnel is from Fishguard, which would generate large amounts of extra freight traffic which the current Severn tunnel – already operating at capacity – could not handle. Additionally, a new high speed rail route has been suggested between London, Bristol, and Cardiff, which faces similar capacity constraints.

If the barrage is built further west, any transport connection would instead link more isolated areas of the Devon-Cornwall peninsula with the cities of South Wales and the ports of Pembrokeshire.