Classic Projects: the Severn Bridge
The story behind the Severn Bridge
The original suspension bridge road crossing linking England and Wales at the Severn Estuary helped economic and industrial development. But the designers seriously under-estimated the growth in traffic volumes...
In keeping with its strategic and economic importance, over the centuries the River Severn has been bridged more than 100 times. Perhaps with the exception of the Iron Bridge at Ironbridge Gorge, none is as iconic as the original motorway suspension toll bridge constructed in the 1960s.
Connecting Aust, Gloucestershire, with Chepstow, Monmouthshire, the Severn Bridge was designed to replace a ferry service that was struggling with road-vehicle traffic-flow after the Second World War. But there was a more pressing economic reason behind servicing the increasing traffic flow into Wales. The decline of the South Wales extraction industries meant that the region desperately needed inward investment. To attract new technologies there needed to be quick and reliable road links with the rest of the UK.
The idea of bridging the Severn at this geographical location had been around since the early 1800s in order to improve mail connections. This need was eventually satisfied by the construction of the Severn Tunnel rail line in 1886. Proposals for a road crossing were then met with stiff opposition from the Great Western Rail Company, which operated the line.
After the Second World War there were ambitious plans to expand Britain's trunk-road network. However, development of the Severn Bridge was postponed to allow work to go ahead on the Forth Road Bridge, with the result that the Severn Bridge project was not properly started until 1961.
Over the course of planning and construction there have been many contractors associated with the project, but broadly speaking the Severn Bridge was designed by Freeman, Fox and Partners, with the substructure construction by John Howard & Co, while the superstructure contractors were Associated Bridge Builders. The term 'bridge' is misleading, as the crossing comprises four separate units. From east to west:
* Aust Viaduct which connects to the first gravity span of the bridge itself;
* Severn Bridge: a conventional suspension bridge spanning the Severn Estuary with deck supported by two cables between two steel towers;
* Beachley Viaduct that crosses a small peninsular of the same name;
* Wye Bridge: a cable-stayed bridge that crosses the border between England and Wales.
When Queen Elizabeth opened the bridge in 1966 the toll for a single car crossing was 2s 6d. Taking into account inflation, this works out at a shade over £2 today, but due to currency depreciation the same journey in 2013 will cost £6. The collection of tolls is a bit of a political hot potato, as only vehicles entering Wales are required to pay. Those exiting have a free run into England. The practical reason for this is to avoid motorists having to queue on the bridge itself in times of heavy use. But campaigners see this as discriminatory, and have accused the government of levying a tax on entering Wales.
With traffic peaking at 50,000 vehicles per day on the original bridge, the requirement for a second crossing was identified. On completion in 1996, the Second Severn Crossing carried a new stretch of M4 into Wales, while the section of the motorway serviced by the original bridge was renamed the M48. The Severn Bridge today carries only 25 per cent of traffic crossing the estuary.
|To start a discussion topic about this article, please log in or register.|
"This issue we honour a national hero, and the subject of Benedict Cumberbatch's latest film, codebreaker Alan Turing"
- Graphene Nobelist set to revolutionise fuel cell tech
- Drift modelling to help find lost MH370
- IET partners with ITN to produce online engineering special
- New hub aims to commercialise quantum tech
- New law will require shipping sector to monitor CO2 emissions
- Launching cubesats from stratospheric balloons
- What to Specialise in Electronics Engineering?? [03:02 am 03/04/14]
- Britain to have just one remaining coal pit by the end of 2015 [01:11 am 03/04/14]
- LV Generator Star point earthing - UK [08:35 pm 02/04/14]
- East West Rail - the Oxford to Bedford route [07:33 pm 02/04/14]
- Small nuclear power [06:06 pm 02/04/14]
The essential source of engineering products and suppliers.