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Bypass

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Bypass
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M6 Preston Bypass - Coppermine - 1302.jpg
The Preston Bypass was Britain's first motorway
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Throughpass
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Relief Road


The Maidenhead Bypass was an early section of M4

A Bypass (historically by-pass or bye-pass) is a section of road constructed so as to avoid a town centre, or other particularly congested area. They are constructed to both reduce delays on a route, and to improve safety on the section of road that has been bypassed. They are usually constructed to a higher standard than that the major route replaced and, while often longer than the route that it replaces, are usually quicker to use.

Sometimes bypasses go around entire urban areas, but occasionally they are an improved route that deliberately passes through a town. These are known as a throughpass, though the Department for Transport in England tends to use relief road, e.g. for the M67 at Denton and the A650 at Bingley.

Bypasses can be problematical. If frontage development is allowed on them (as is often the case with commercial development), then the new road can become just as congested as the old road (sometimes more so), and the traffic flow improvement is reduced. Sometimes this requires that a second (or even third) bypass is constructed. Shrewsbury, Shropshire is famous for having two bypasses, whilst Willenhall, Staffordshire and Dartford, Kent have had three constructed; although in the latter case, not all relieving the same route.

Construction of bypasses can be controversial. By their very nature, the new road (unless it is a throughpass) passes through a rural area surrounding a town, which can lead to environmental concerns and protest such as during the construction of the A34 Newbury Bypass in Berkshire. This concern conflicts with other concerns regarding traffic safety and pollution caused by stationary traffic in the town being bypassed. There are also occasions where bypasses are not wanted by communities due to fears of loss of trade. Most villages along the old routes have lost their local petrol stations and roadside cafés because of the loss of passing trade.

Many of the long distance motorways within Great Britain were constructed as a series of bypasses that were joined together, for example, sections of the M6 include the Preston Bypass, Lancaster bypass, Stafford bypass, Penrith bypass and Carlisle bypass, each of which was opened before its adjacent sections to north and south; whilst the first section of M54 opened as the Wellington bypass; and sections of M4 include the Maidenhead bypass, the Slough bypass, the Newport bypass and the Port Talbot bypass. In the early days of motorway construction, temporary numbers were often allocated to these short bypasses, for example, the M20 Maidstone bypass was originally allocated A20(M); and the Port Talbot bypass allocated A48(M). Sometimes these very early allocations were not used when the motorway opened - for example, the A8(M) Renfrew bypass opened as M8.




Bypass
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