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The Second Severn Crossing ((ウェールズ語:Ail Groesfan Hafren)) is the M4 motorway bridge over the River Severn between England and Wales, inaugurated on 5 June 1996 by HRH The Prince of Wales to augment the traffic capacity of the original Severn Bridge built in 1966. The bridge marks the lower limit of the River Severn and the start of the Severn Estuary. Its location is farther to the south than the old bridge and, being more in line with the landward sides of the M4 motorway, is a shorter journey when travelling between England and South Wales. The junctions at each end are designed for most traffic to use this crossing – to use the old Severn Bridge crossing one has to leave the M4 and join the M48 motorway either at Aust or near Magor. The new crossing carries more traffic than the Severn Bridge, which is still in use. It is wider than the Severn Bridge, having three lanes and narrow hard shoulder each way, compared with the two lanes, cycle path and footpath of the original crossing. The path taken by the bridge is close to that of the Severn Tunnel which has carried the railway line beneath the river bed since 1886. Much of the estuary is mudflats at low tide, but at high tide can be covered by up to 14 metres of water. This presented the engineers with a unique set of constraints with packets of work being scheduled at low tide and being completed with the short windows allowed by the tides. The concession given to the consortium which financed, built and operate the bridge required them to take over the outstanding debt on the original Severn Bridge and to operate the two bridges as a single entity. Tolls are set annually by the government based on the change in the previous year's Retail Price Index. On the expiry of the concession the consortium is required to hand the bridge over into public ownership. It was reported in 2012, that the process of repayment was likely to continue until the early 2020s due to the introduction of a revised settlement to the operator in return for accepting payment by debit and credit cards. As part of the announcement, it was stated that even after repayment was complete the toll charge would likely remain at the same levels.〔http://www.bbc.co.uk/news/uk-wales-19967175〕 ==Background== The Severn Estuary presented a barrier between the Bristol area and South Wales. The estuary has a maximum tidal range of 14.5 metres, the second highest in the world and during a rising or falling tide, strong currents of up to 8 knots (4 m/s). Much of the estuary is mud flats that are exposed at low tide that have been designated a Special Protection Area. The central part of the estuary is a navigable channel which, at the site of the bridge, is known as "The Shoots". The bridge is upstream from Avonmouth and the Port of Bristol, but downstream from the Port of Sharpness. The Gloucester Harbour Trustees have responsibility for controlling navigation in the estuary's tidal waters upstream from the bridge.〔(【引用サイトリンク】Gloucester Harbour Trustees: About the trustees )〕 Until 1966, road travellers had the option of either using the Aust Ferry which had operated since medieval times (and as a car ferry since 1926) or by making the detour via Gloucester.〔Journeys between Newport and Bath are reduced from 161 km to 69 km -(ViaMichelin ).〕 In 1966 the first Severn road bridge, a four-lane suspension bridge was opened carrying the M4 motorway from England into South Wales. By 1984 traffic across the first Severn Bridge had tripled and it was projected that by the mid-1990s the old bridge would be running at capacity. A study was commissioned into the building of a second crossing – either a tunnel or a bridge. The consultants reported back in 1986 recommending that a new bridge be built downstream from the existing bridge.〔(【引用サイトリンク】Second Severn Crossing )〕 In 1988 it was announced that tenders would be invited from private consortia to fund, build and operate the bridge for as specified period. The consortium would also take over the management and the £100 million debt of the old bridge. Tenders were invited in 1989 and in 1990 the concession to build the bridge was awarded to Severn River Crossing plc.〔(【引用サイトリンク】The Severn Crossing – Facts and Figures )〕 Construction work started on 26 April 1992 and the bridge was opened by the Prince of Wales on 5 June 1996.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Second Severn Crossing」の詳細全文を読む スポンサード リンク
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