Crossings
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| Bridges • Tunnels • Causeways • Ferries | ||
This page is intended to give a brief outline of the different types of Crossings found on British and Irish . Please follow the links below to gain more detail on a specific type.
In terms of the road network, a crossing is a means of carrying a road across an obstacle, be that a river, railway, another road, and so on. The most common form therefore is the Bridge, but the term also encompasses Causeways, Culverts, Tunnels, Ferries, and in a broader sense, Cuttings and Embankments and Hill Passes.
Bridges
Bridges are by far and away the most common form of crossing on the British and Irish road network. They quickly and efficiently carry roads over numerous obstacles, including Rivers, Canals, Railways, Channels between islands and, of course, other roads. The oldest bridges still in common use are generally masonry Arch Bridges, but over the last century the bridge has developed numerous other forms. The simplest are Girder Bridges or Concrete Bridges, utilising a simple beam or slab to span the obstacle. These, in turn, have developed into Suspension Bridges and Cable Stayed Bridges to span wider channels or (in other parts of the world more than the UK) wide valleys. Multiple spans have also been used to form viaducts, either to cross valleys, or elevate a road in an urban area.
A development of the standard bridge theme is the Moving Bridge, which can be moved out of the way of the water course (normally) to allow unrestricted movement of tall vessels. The two most common form of Moving Bridges are Swing Bridges and Lifting Bridges.
Culverts
A culvert is essentially a very small bridge, these days usually constructed by placing large pipes under the road to carry the water course. In the past, Box Culverts were often constructed, using stone slabs on top of stone walls to form the pipe. There are also a few instances these days of pipes under roads which are large enough to also carry a farm track. This is in some respects a very cheap and easy way of constructing a bridge, but requires the right ground conditions and other factors to be a viable option.
Causeways
A Causeway is a structure which crosses water, or a flood plain, with an elevated roadway. Although there is normally a bridge section incorporated in the overall structure, this is usually only a small proportion of the overall length. Causeways are widely used in the Scottish Highlands and Islands, both to link islands together, cross lochs and inlets and also to simply cross boggy ground near a loch or river. Some of the structures referred to as Causeways have long, low lying, bridge sections incorporated in the, such as the Kyle of Tongue Causeway, while others, like the Churchill Barriers either have no means of water passing from one side to the other, or rely on water filtering through the rock / concrete banks beneath the road. The tradition of building Causeways in the far north of Scotland is very old, with Crannogs - houses built on stilts in lochs - dating back thousands of years using causeways to reach them, albeit often just submerged beneath the surface to hide it from unwelcome visitors.
The other common form of Causeway is effectively little more than a road across a beach, such as the Lindisfarne Causeway, or the causeways connecting the tidal islands in the estuaries around the Essex Coast.
Tunnels
Across Europe, Tunnels are a common means of carrying a road through difficult terrain. However, for a number of reasons, despite being common on our rail networks, they have been avoided by British road engineers. The most common types of tunnel in Britain are Cut and Cover or simply overbuilt structures, where either a trench is dug and then roofed over, or a road simply becomes a tunnel when buildings are erected above it, such as the M8 tunnel in central Glasgow (right). In both instances most are short, measured in hundreds of metres. There are a few road tunnels under rivers in the UK, the Clyde Tunnel in Scotland, Conwy Tunnel in Wales, Tyne Tunnel in northern England, and several which pass under the Thames in London.
Ferries
Being Island nations, both the UK and Ireland rely on Ferries to connect their road networks to mainland Europe. There are also numerous ferry routes within our islands, not just connecting the numerous islands together, but also providing short cuts across river estuaries and harbour areas, as well as the Windermere Ferry, the last inland vehicle ferry still operating in the UK. Since 1950 numerous ferry services have been replaced by bridges, or fallen into disuse as more and more people use cars rather than walking or riding, meaning that the former shortcuts are no longer so useful.
Lists of Crossings by County
Lists of Crossings by Authority
