Forth Road Bridge

2007 Schools Wikipedia Selection. Related subjects: Engineering; Road transport

Forth Road Bridge

The Forth Road Bridge, viewed from the Fife side, straddling the Firth of Forth.
Official name	Forth Road Bridge
Carries	Motor vehicles ( A90 road) Cyclists ( National Cycle Route 1) Pedestrians
Crosses	Firth of Forth
Locale	Edinburgh, Scotland
Maintained by	Forth Estuary Transport Authority
Design	Suspension bridge
Longest span	1006 m (3298 ft)
Total length	2512 m (8242 ft)
Width	Dual two-lane carriageway, two cycle/footpaths (total width 33 m)
Clearance below	44.3 m
AADT	~32,000 vehicles (2004 estimate)
Opening date	4 September 1964
Toll	Motorcycles - free Cars - £1 Goods vehicles - £2

The Forth Road Bridge is a suspension bridge in east central Scotland. The bridge, built in 1964, spans the Firth of Forth, connecting the capital city Edinburgh at South Queensferry to Fife at North Queensferry. The toll bridge replaced a centuries-old ferry service to carry vehicular traffic, cyclists, and pedestrians across the Forth; rail crossings are made by the adjacent and historic Forth Bridge.

Issues regarding the continued tolling of the bridge, and those over its deteriorating condition and proposals to have it replaced or supplemented by an additional crossing, have caused it to become something of a political football for the Scottish Parliament.

History

The first crossing at what is now the site of the bridge was established in the 11th century by Margaret, queen consort of King Malcolm III, who founded a ferry service to transport religious pilgrims from Edinburgh to Dunfermline Abbey and St Andrews. Its creation gave rise to the port towns which remain to this day, and the service remained in uninterrupted use as a passenger ferry for over eight hundred years. As early as the 1740s there were proposals for a road crossing at the site, although their viability was only considered following the construction of the first Forth bridge in 1890.

The importance of the crossing to vehicular traffic was underpinned when the Great Britain road numbering scheme was drawn up in the 1920s. The planners wished the arterial A9 road to be routed across the Forth here, although the unwillingness to have a ferry crossing as part of this route led to the A90 number being assigned instead.

There was a period of renewed lobbying for a road crossing in the 1920s and 1930s, at which time the only vehicle crossing was a single passenger and vehicle ferry. Sir William Denny championed the expansion of that service in the 1930s, providing and operating two additional ferries on behalf of the London and North Eastern Railway that aimed to supplement the services of the adjacent railway bridge. Their success allowed for the addition of two more craft in the 1940s and 1950s, by which time the ferries were making 40,000 crossings, carrying 1.5 million passengers and 800,000 vehicles annually.

With the then-newest and nearest bridge spanning the Forth (the Kincardine Bridge, built in 1936) still around fifteen miles upstream, the upsurge in demand for a road crossing between Edinburgh and Fife prompted the UK government establish the Forth Road Bridge Joint Board by Act of Parliament in 1947 to oversee the implementation of a new bridge to replace the ferry service. The final construction plan was accepted in February 1958 and work began later that year.

Mott, Hay and Anderson and Freeman Fox & Partners designed and constructed the bridge at a cost of £11.5 million, while the total cost of the project including road connections and realignments was £19.5 million. Seven lives were lost during construction before the bridge was opened by Queen Elizabeth II and the Duke of Edinburgh on 4 September 1964. The ferry service was discontinued as of that date. The bridge's management was delegated to the FRBJB, and remained so until 2002 when its operation was transferred to a new body with a wider remit, the Forth Estuary Transport Authority.

Statistics

High-tensile wires suspending the deck of the northbound carriageway.

The bridge's central main span is 1006 m (3298 ft) long, its two side spans are each 408 m (1338 ft) long, and the approach viaducts are 252 m (827 ft) on the north side and 438 m (1437 ft) on the south side; at a total length of 2512 m (8242 ft), it was the longest suspension bridge outside the United States and the fourth-largest in the world at the time of its construction. The bridge comprises 39,000 tons of steel and 115,000 cubic metres of concrete. Its width comprises a dual carriageway road with two lanes in each direction bounded by cycle/footpaths on each side. The main strung cables are 590 mm in diameter and each carries 13,800 tonnes of the bridge's load by suspending 11,618 5 mm diameter high tensile wires.

The bridge forms a crucial part of the corridor between south-east and north-east Scotland, linking Edinburgh to Perth, Dundee and Aberdeen by the A90 road and its sister M90 motorway which begins at the bridge's northern terminus. The bridge carried around 2.5 million vehicles in its first year but this figure has risen steadily over time to around 11.8 million vehicles in 2004. The bridge carried its 250 millionth vehicle in 2002.

It was awared Historic Scotland's Category A listed structure status in 2001.

Tolling issues

The bridge has been tolled since opening to pay for the cost of construction and maintenance. The current toll is £1 for most vehicular traffic, increased from 80p in October 2005. The toll for buses with over sixteen seats is £1.40, and most goods vehicles pay £2.

Initially, it was suggested that tolling would cease once the original cost of construction plus interest accrued had been repaid - this was done in 1993 and tolls were slated for removal by May 1995. However, the legislation enabling the levying of tolls has instead been renewed by Parliament (originally that of the UK but now the responsibility of the Scottish Parliament) on three separate occasions in 1998, 2003 and 2006.

Originally, a toll was paid for each direction of travel with sets of toll booths on both carriageways. In 1997, a decision was made to double the northbound toll (then 40p, to 80p) and remove the southbound toll. The belief was that almost all traffic makes a return journey across the bridge, resulting in a reduction of congestion for southbound traffic without reducing overall toll revenues.

The Forth Estuary Transport Authority (FETA) has justified the continued use of tolls by suggesting they are necessary for a raft of maintenance and improvement works. These include the construction of defences around the submerged piers forming the bases of the main towers in the event of collision in the Firth. The main towers have also been strengthened with internal steel columns (the original tower structure having been hollow) and had hydraulic rams jack up these sections to transfer a portion of the load to the new steelwork. Also, the vertical cables suspending the deck have had their bolts replaced after a single detected failure. A new paint system required development for the bridge (the original having been phased out due to environmental concerns) and the toll plaza and booths have been replaced allowing more comfort for toll-collection staff and the introduction of electronic tolling.

Variable tolling proposals

In late 2005, FETA's committee approved a proposal for a complete revamp of the system of toll levies. The minimum toll would be set to the existing £1 figure, but would increase dependent on the time of day, rising to a maximum of £4 for evening rush hour travel. All tolls would be halved for cars with more than one occupant, as an incentive to drivers to share cars and make fewer journeys. According to FETA's chairman Lawrence Marshall, the system would provide the most efficiency, claiming that 80% of peak-time journeys are made by single-occupant vehicles. The proposal, passed with the chairman's casting vote after the committee was deadlocked, was referred to the Scottish Executive in December 2005, and implementation planned for October 2007 subject to approval by transport minister Tavish Scott. Environmental groups welcomed the proposal, although local politicians condemned it as simply a means of raising capital. At the same time, a counter-argument was tabled by Fife councillors proposing the complete removal of tolls..

The Scottish Parliament debated the proposals in January 2006, and the affair became a major political issue after Westminster-based MPs Gordon Brown and Alistair Darling ( Chancellor of the Exchequer and Secretary of State for Scotland respectively) were seen to describe the variable tolling plan as "dead in the water". Scottish First Minister Jack McConnell insisted his Labour Party colleagues were misquoted and himself refused to rule out the plan, receiving considerable condemnation from the opposition Scottish National Party.

The political situation was particularly important given that by late January 2006, campaigning was well underway for a by-election scheduled to take place for the Westminster constituency of Dunfermline and West Fife in which the north end of the bridge is situated. The by-election, scheduled for February 9, was contested by - in addition to the major political parties in Scotland - an Abolish Forth Bridge Tolls Party. It was eventually won by Liberal Democrat candidate Willie Rennie, overturning a large Labour majority on a 16% swing.

In the aftermath of the by-election defeat, media speculation suggested the Executive had turned against the proposals, and Tavish Scott eventually confirmed their rejection and the retention of the existing toll structure on 1 March. FETA condemned the decision, while local opposition MSPs charged the minister that his tolling review short-changed Fifers as tolls were axed on the Erskine Bridge leaving tolls on only the Forth and Tay Road Bridge, both in Fife.

Structural issues

An inspection of the integrity of the cables underway on the bridge.

There has been concern at FETA over the structural wear-and-tear of the bridge. The planned theoretical capacity for the bridge (30,000 vehicles per day) is routinely exceeded as traffic levels have outstripped predictions. FETA predicts the demand will rise to an average of 40,000 vehicles per day by 2010 and the Scottish Executive admit that 60,000 vehicles is not uncommon for weekday travel. This has raised concerns about the lifespan of the bridge, originally planned at 120 years.

2003 saw an inspection programme launched (at a cost of £1.2 million) to assess the condition of the bridge cables after excessive corrosion was discovered in a number of bridges in the United States of a similar design, size, and era. The study, which was completed in 2004, found that 22 (out of over 11,000) high-tensile steel wires are known to have snapped. There have been allegations of poor workmanship on the bridge which, combined with the adverse weather while it was being constructed, has led to speculation that these steel wires have become crossed instead of being parallel as intended.

Further investigation of the implications of this is underway, with a study using listening devices to monitor any further strands snapping and pinpoint their location within the main cables. The traffic loads and worries over corrosion have halved the bridge's predicted lifespan to just 50-60 years; there are fears a ban on heavy goods traffic will be necessary by 2013, due to the severe stress the traffic loading has on the bridge and internal corrosion of the steel cables. A full closure is feared to be necessary by 2020.

A number of options are being considered to increase the bridge's lifespan. These include an extensive dehumidification programme to slow the corrosion rate of the cables. Engineering consultants Faber Maunsell expect to begin work on the project in 2006. The works, if approved, are planned to take two years at a cost of £12 million. As part of the works, some of the corroded cable strands are to be spliced.

Proposals for a new Forth Road Bridge

The Forth Bridges, with the road bridge crossing to the left of the rail bridge.

With a complete closure of the existing Forth Road Bridge predicted by approximately 2020 without drastic action, there is a threat of serious economic consequences, due to the strategic importance of the bridge in the Scottish transport network and the estimated 10+ year timescale for construction of a replacement.

Proposals for an additional road crossing had initially been drawn up in the early 1990s, but met stiff opposition from environmentalists and from Edinburgh City Council on the grounds of the increased traffic it would generate. Following the Labour victory in the 1997 General Election, the proposals were shelved; however, they have resurfaced as of 2005, given the concerns over the existing bridge's lifespan. A new bridge, either as a complement to the existing bridge or as a complete replacement, is now under consideration by FETA, with its cost estimated at £700 million. There remains considerable opposition to the project on the same grounds as before, particularly from the Scottish Green Party.

A decision on the proposal is expected by Easter 2006.