Channel Tunnel

Caption	Map of the Channel Tunnel
Location	English Channel (Strait of Dover)
Coordinates	Folkestone: Coquelles:
Status	Active
Start	Folkestone, Kent, United Kingdom
End	Coquelles, Pas-de-Calais, France
Open	6 May 1994 (tunnel)14 November 1994 (passenger service)
Owner	Eurotunnel
Operator	EurotunnelEurostarDB Schenker Rail (UK)SNCF
Character	Through-rail passenger and freight. Vehicle shuttle.
Linelength
Notrack	2 single track tunnels1 service tunnel
Gauge	(standard gauge)
El	25 kV AC OHLE

The Channel Tunnel (), (also referred to as the Chunnel) is a undersea rail tunnel linking Folkestone, Kent in England with Coquelles, Pas-de-Calais near Calais in northern France beneath the English Channel at the Strait of Dover. At its lowest point, it is deep. At , the Channel Tunnel possesses the longest undersea portion of any tunnel in the world, although the Seikan Tunnel in Japan is both longer overall at , and deeper at below sea level.

The tunnel carries high-speed Eurostar passenger trains, Eurotunnel Shuttle roll-on/roll-off vehicle transport—the largest in the world—and international rail freight trains. but British political and press pressure over compromised national security stalled attempts to construct a tunnel. causing a minor diplomatic disagreement over the siting of the Sangatte refugee camp, which was eventually closed in 2002.

Origins

Proposals and attempts

In 1802, French mining engineer Albert Mathieu put forward a proposal to tunnel under the English Channel, with illumination from oil lamps, horse-drawn coaches, and an artificial island mid-Channel for changing horses.

In the 1830s, Frenchman Aimé Thomé de Gamond performed the first geological and hydrographical surveys on the Channel, between Calais and Dover. Thomé de Gamond explored several schemes and, in 1856, he presented a proposal to Napoleon III for a mined railway tunnel from Cap Gris-Nez to Eastwater Point with a port/airshaft on the Varne sandbank at a cost of 170 million francs, or less than £7 million.

mid-Channel]]

In 1865, a deputation led by George Ward Hunt proposed the idea of a tunnel to the Chancellor of the Exchequer of the day, William Ewart Gladstone.

After 1867, William Low and Sir John Clarke Hawkshaw promoted ideas, but none were implemented. An official Anglo-French protocol was established in 1876 for a cross-Channel railway tunnel. In 1881, British railway entrepreneur Sir William Watkin and French Suez Canal contractor Alexandre Lavalley were in the Anglo-French Submarine Railway Company that conducted exploratory work on both sides of the Channel. On the English side a diameter Beaumont-English boring machine dug a pilot tunnel from Shakespeare Cliff. On the French side, a similar machine dug from Sangatte. The project was abandoned in May 1882, owing to British political and press campaigns advocating that a tunnel would compromise Britain's national defences.

In 1955, defence arguments were accepted to be irrelevant because of the dominance of air power; thus, both the British and French governments supported technical and geological surveys. Construction work commenced on both sides of the Channel in 1974, a government-funded project using twin tunnels on either side of a service tunnel, with capability for car shuttle wagons. In January 1975, to the dismay of the French partners, the British government cancelled the project. The government had changed to the Labour Party and there was uncertainty about EEC membership, cost estimates had ballooned to 200% and the national economy was troubled. By this time the British Priestly tunnel boring machine was ready and the Ministry of Transport was able to do a experimental drive.

Arrangement

The British Channel Tunnel Group consisted of two banks and five construction companies, while their French counterparts, France–Manche, consisted of three banks and five construction companies. The role of the banks was to advise on financing and secure loan commitments. On 2 July 1985, the groups formed Channel Tunnel Group/France–Manche (CTG/F–M). Their submission to the British and French governments was drawn from the 1975 project, including 11 volumes and a substantial environmental impact statement.

In France, with its long tradition of infrastructure investment, the project garnered widespread approval and in April the French National Assembly gave unanimous support and, in June 1987, after a public inquiry, the Senate gave unanimous support. In Britain, select committees examined the proposal, making history by holding hearings outside of Westminster, in Kent. In February 1987, the third reading of the Channel Tunnel Bill took place in the House of Commons, and was carried by 94 votes to 22. The Channel Tunnel Act gained Royal assent and passed into English law in July of that year.

The Channel Tunnel is a build-own-operate-transfer (BOOT) project with a concession. TML would design and build the tunnel, but financing was through a separate legal entity: Eurotunnel. Eurotunnel absorbed CTG/F-M and signed a construction contract with TML; however, the British and French governments controlled final engineering and safety decisions, which are now in the hands of the Channel Tunnel Safety Authority. The British and French governments gave Eurotunnel a 55- (later 65-) year operating concession to repay loans and pay dividends. A Railway Usage Agreement was signed between Eurotunnel, British Rail and the Société Nationale des Chemins de fer Français guaranteeing future revenue in exchange for the railways obtaining half of the tunnel's capacity.

Private funding for such a complex infrastructure project was of unprecedented scale. An initial equity of £45 million was raised by CTG/F-M, increased by £206 million private institutional placement, £770 million was raised in a public share offer that included press and television advertisements, a syndicated bank loan and letter of credit arranged £5 billion. The cost overrun was partly due to enhanced safety, security, and environmental demands.

Construction

Eleven tunnel boring machines, working from both sides (England to France) of the Channel, cut through chalk marl to construct two rail tunnels and a service tunnel. The vehicle shuttle terminals are at Cheriton (part of Folkestone) and Coquelles, and are connected to the English and French motorways (M20 and A16 respectively).

Tunnelling commenced in 1988, and the tunnel began operating in 1994. In 1985 prices, the total construction cost was £4.650 billion (equivalent to £ billion today), an 80% cost overrun. At the peak of construction 15,000 people were employed with daily expenditure over £3 million. Ten workers, eight of them British, were killed during construction between 1987 and 1993, most in the first few months of boring.

Completion

and French President François Mitterrand]]

A small, two-inch (50-mm) diameter pilot hole allowed the service tunnel to break through without ceremony on 30 October 1990. On 1 December 1990, Englishman Graham Fagg and Frenchman Phillippe Cozette broke through the service tunnel with the media watching. Eurotunnel completed the tunnel on time, Following the ceremony President Mitterrand and the Queen travelled on Le Shuttle to a similar ceremony in Folkestone. replacing the original slower link to Waterloo International railway station. On High Speed 1 trains travelling at speeds up to , the journey from London to Paris takes 2 hours 15 minutes and London to Brussels takes 1 hour 51 minutes.

In 1996, the American Society of Civil Engineers, with Popular Mechanics, selected the tunnel as one of the Seven Wonders of the Modern World.

Engineering

in York, England, showing the circular cross section of the tunnel with the overhead line powering a Eurostar train. Also visible is the segmented tunnel lining]]

Surveying undertaken in the twenty years before tunnel construction confirmed earlier speculations that a tunnel route could be bored through a chalk marl stratum. The chalk marl was conducive to tunnelling, with impermeability, ease of excavation and strength. While on the English side the chalk marl ran along the entire length of the tunnel, on the French side a length of had variable and difficult geology. The Channel Tunnel consists of three bores: two diameter rail tunnels, apart, in length with a diameter service tunnel in between. There are also cross-passages and piston relief ducts. The service tunnel was used as a pilot tunnel, boring ahead of the main tunnels to determine the conditions. English access was provided at Shakespeare Cliff, while French access came from a shaft at Sangatte. The French side used five tunnel boring machines (TBMs), the English side used six. The service tunnel uses Service Tunnel Transport System (STTS) and Light Service Tunnel Vehicles (LADOGS). Fire safety was a critical design issue.

Between the portals at Beussingue and Castle Hill the tunnel is long, with under land on the French side, under land on the UK side and under sea. This makes the Channel Tunnel the second longest rail tunnel in the world, behind the Seikan Tunnel in Japan, but with the longest under-sea section. The average depth is below the seabed. On the UK side, of the expected of spoil approximately was used for fill at the terminal site, and the remainder was deposited at Lower Shakespeare Cliff behind a seawall, reclaiming This land was then made into the Samphire Hoe Country Park. Environmental impact assessment did not identify any major risks for the project, and further studies into safety, noise, and air pollution were overall positive. However, environmental objections were raised over a high-speed link to London.

Geology

Successful tunnelling under the channel required a sound understanding of the topography and geology and the selection of the best rock strata through which to tunnel. The geology generally consists of northeasterly dipping Cretaceous strata, part of the northern limb of the Wealden-Boulonnais dome. Characteristics include:

Continuous chalk on the cliffs on either side of the Channel containing no major faulting, as observed by Verstegan in 1698

Four geological strata, marine sediments laid down 90–100 million years ago; pervious upper and middle chalk above slightly pervious lower chalk and finally impermeable Gault Clay. A sandy stratum, glauconitic marl (tortia), is in between the chalk marl and gault clay

A layer of chalk marl (French: craie bleue) in the lower third of the lower chalk appeared to present the best tunnelling medium. The chalk has a clay content of 30–40% providing impermeability to groundwater yet relatively easy excavation with strength allowing minimal support. Ideally the tunnel would be bored in the bottom of the chalk marl, allowing water inflow from fractures and joints to be minimised, but above the gault clay that would increase stress on the tunnel lining and swell and soften when wet.

On the English side of the channel, the strata dip less than 5°, however, on the French side, this increases to 20°. Jointing and faulting is present on both the English and French sides. On the English side, only minor faults of displacement less than exist. On the French side, displacements of up to are present owing to the Quenocs anticlinal fold. The faults are of limited width, filled with calcite, pyrite and remoulded clay. The increased dip and faulting restricted the selection of route on the French side. To avoid confusion, microfossil assemblages were used to classify the chalk marl. On the French side, particularly near the coast, the chalk was harder, and more brittle, and more fractured than on the English side. This led to the adoption of different tunnelling techniques on the French and English sides.

Surveying

Marine soundings and samplings by Thomé de Gamond were carried out during 1833–1867, establishing the seabed depth at a maximum of and the continuity of geological strata (layers). Surveying continued over many years, with 166 marine and 70 land-deep boreholes being drilled and over 4,000-line-kilometres of marine geophysical survey completed.

Tunnelling

Tunnelling between England and France was a major engineering challenge, with the only precedent being the undersea Seikan Tunnel in Japan. A serious risk with underwater tunnels is major water inflow due to the water pressure from the sea above under weak ground conditions. The Channel Tunnel also had the challenge of time—being privately funded, early financial return was paramount.

The objective was to construct: two diameter rail tunnels, apart, in length; a diameter service tunnel between the two main tunnels; pairs of diameter cross-passages linking the rail tunnels to the service tunnel at spacing; piston relief ducts diameter connecting the rail tunnels at spacing; two undersea crossover caverns to connect the rail tunnels. The service tunnel always preceded the main tunnels by at least to ascertain the ground conditions. There was plenty of experience with tunnelling through chalk in the mining industry. The undersea crossover caverns were a complex engineering problem. The French cavern was based on the Mount Baker Ridge freeway tunnel in the USA. The UK cavern was dug from the service tunnel ahead of the main tunnels to avoid delay.

Precast segmental linings in the main TBM drives were used, but different solutions were used on the English and French sides. On the French side, neoprene and grout sealed bolted linings made of cast iron or high-strength reinforced concrete were used. On the English side, the main requirement was for speed and bolting of cast-iron lining segments was only carried out in areas of poor geology. In the UK rail tunnels, eight lining segments plus a key segment were used; on the French side, five segments plus a key segment. On the French side, a diameter deep grout-curtained shaft at Sangatte was used for access. On the English side, a marshalling area was below the top of Shakespeare Cliff, and the New Austrian Tunnelling method (NATM) was first applied in the chalk marl here. On the English side, the land tunnels were driven from Shakespeare Cliff, the same place as the marine tunnels, not from Folkestone. The platform at the base of the cliff was not large enough for all of the drives and, despite environmental objections, tunnel spoil was placed behind a reinforced concrete seawall, on condition of placing the chalk in an enclosed lagoon to avoid wide dispersal of chalk fines. Owing to limited space, the precast lining factory was on the Isle of Grain in the Thames estuary. Six machines were used, all commenced digging from Shakespeare Cliff, three marine-bound and three for the land tunnels. A 900 mm gauge railway was used on the English side during construction.

In contrast to the English machines, which were simply given alphanumeric names, the French tunnelling machines were all named after women: Brigitte, Europa, Catherine, Virginie, Pascaline, Séverine.

Railway design

, a vehicle shuttle train. The largest railway wagons in the world,

Power supply

All tunnel services run on electricity, shared equally from English and French sources. Power is delivered to the locomotives via an overhead line (catenary) at .

A large proportion of the railway south of London uses a 750 V DC third rail to deliver electrical power; however since the opening of High Speed 1 there is no need to use the third rail system for any part of the Eurostar journey. High Speed 1, the tunnel itself and the route to Paris has power provided via overhead catenary at 25 kV 50 Hz. The railways on "classic" lines in Belgium are also electrified by overhead catenaries, but at 3000 V DC. The maximum allowed speed is .

Track system

The American Sonneville International Corporation track system consisting of UIC60 rails on 900A grade resting on microcellular EVA pads, bolted into concrete was chosen. The larger European GB+ loading gauge was used rather than one of the smaller UK alternatives; this gauge is maintained on High Speed 1 as far as Barking in east London. Ballasted track was ruled out owing to maintenance constraints and a need for geometric stability.

Rolling stock

Eurotunnel Shuttle

Initially 38 Le Shuttle locomotives were commissioned, working in pairs with one at each end of a shuttle train. The shuttles have two separate halves: single and double deck. Each half has two loading/unloading wagons and twelve carrier wagons. Eurotunnel's original order was for nine tourist shuttles.

HGV shuttles also have two halves, with each half containing one loading wagon, one unloading wagon and 14 carrier wagons. There is a club car behind the leading locomotive. Eurotunnel originally ordered six HGV shuttles rakes.

Freight locomotives

Forty-six Class 92 locomotives for hauling freight trains and overnight passenger trains (the Nightstar project, which was abandoned) were commissioned, which can run on both overhead AC and third-rail DC power.

International passenger

Thirty-one Eurostar trains—based on the French TGV—built to UK loading gauge, and with many modifications for safety within the tunnel, were commissioned, with split ownership between British Rail, French National Railway Company and National Railway Company of Belgium. British Rail ordered seven more for services north of London.

At the end of 2009, extensive fire-proofing requirements were dropped and Deutsche Bahn received permission to run German Intercity-Express (ICE) trains through the Channel Tunnel in the future. On 19 October 2010 Deutsche Bahn ran the first ICE train through the Channel Tunnel arriving in St. Pancras after evacuation tests in the tunnel were a success.

Service locomotives

Diesel locomotives for rescue and shunting work are Eurotunnel Class 0001 and Eurotunnel Class 0031.

Operation

Usage and services

of freight. Freight vehicle shuttle numbers dropped in 1996/7 owing to closure of the service after the November 1996 fire]] in west Folkestone. The terminal services shuttle trains that carry vehicles, and is linked to the M20 motorway]] is the last view of England for most passengers embarking at the Cheriton terminal]]

Services offered by the tunnel are:

Eurotunnel Shuttle (formerly Le Shuttle) roll-on roll-off shuttle service for road vehicles,

Eurostar passenger trains,

through freight trains.

Both the freight and passenger traffic forecasts that led to the construction of the tunnel were largely and universally overestimated. Particularly, Eurotunnel's commissioned forecasts were over-predictions. Eurostar passenger numbers continued to increase, reaching 9,528,558 in 2010.

{| class="wikitable" |- !ROWSPAN="2" |  Year  !COLSPAN="3" | Passengers transported... |- ! by Eurostar(actual ticket sales) !! by Eurotunnel Passenger Shuttles Through freight volumes peaked in 1998 at 3.1 million tonnes. However, with continuing problems, this figure fell back to 1.21 million tonnes in 2007, increasing again slightly to 1.24 million tonnes in 2008. | 16.7 | 18.4 |- | 2004 | 1,889,175 | 17.0 | 18.6 |- | 2006 | 1,569,429 | 18.4 | 19.6 |- | 2008 | 1,239,445 | 10.0 | 11.2 |- | 2010 | 1,128,079 In September 2006 EWS, the UK's largest rail freight operator, announced that owing to cessation of UK-French government subsidies of £52 million per annum to cover the Channel Tunnel "Minimum User Charge" (a subsidy of around £13,000 per train, at a traffic level of 4,000 trains per annum), freight trains would stop running after 30 November.

Economic performance

Shares in Eurotunnel were issued at £3.50 per share on 9 December 1987. By mid-1989 the price had risen to £11.00. Delays and cost overruns led to the share price dropping; during demonstration runs in October 1994 the share price reached an all-time low value. Eurotunnel suspended payment on its debt in September 1995 to avoid bankruptcy. In December 1997 the British and French governments extended Eurotunnel's operating concession by 34 years to 2086. Financial restructuring of Eurotunnel occurred in mid-1998, reducing debt and financial charges. Despite the restructuring The Economist reported in 1998 that to break even Eurotunnel would have to increase fares, traffic and market share for sustainability. A cost benefit analysis of the Channel Tunnel indicated that there were few impacts on the wider economy and few developments associated with the project, and that the British economy would have been better off if the tunnel had not been constructed.

Under the terms of the Concession, Eurotunnel was obliged to investigate a cross-Channel road tunnel. In December 1999 road and rail tunnel proposals were presented to the British and French governments, but it was stressed that there was not enough demand for a second tunnel. A three-way treaty between the United Kingdom, France and Belgium governs border controls, with the establishment of control zones wherein the officers of the other nation may exercise limited customs and law enforcement powers. For most purposes these are at either end of the tunnel, with the French border controls on the UK side of the tunnel and vice versa. For certain city-to-city trains, the train itself represents a control zone. A binational emergency plan coordinates UK and French emergency activities.

In 1999 Eurostar posted its first ever net profits, having previously made a loss of £925m in 1995. At Folkestone there are of mainline track and 45 turnouts with eight platforms. At Calais there are of track with 44 turnouts. At the terminals the shuttle trains traverse a figure eight to reduce uneven wear on the wheels. Kent's regional development would benefit from the tunnel, but being so close to London restricts the benefits. Gains are in the traditional industries and are largely dependent on the development of Ashford International passenger station, without which Kent would be totally dependent on London's expansion. Nord-Pas-de-Calais enjoys a strong internal symbolic effect of the Tunnel which results in significant gains in manufacturing.

The removal of a bottleneck by means like the Channel Tunnel does not necessarily induce economic gains in all adjacent regions, the image of a region being connected to the European high-speed transport and active political response are more important for regional economic development. However, some small-medium enterprises located in the immediate vicinity of the terminal have used the opportunity to re-brand the profile of their business with positive effect, such as The New Inn at Etchinghill which was able to commercially exploit its unique selling point as being 'the closest pub to the Channel Tunnel'. Tunnel-induced regional development is small compared to general economic growth. The South East of England is likely to benefit developmentally and socially from faster and cheaper transport to continental Europe, but the benefits are unlikely to be equally distributed throughout the region. The overall environmental impact is almost certainly negative.

Five years after the opening of the tunnel, there were few and small impacts on the wider economy, and it was difficult to identify major developments associated with the tunnel. It has been postulated that the British economy would have actually been better off without the costs from the construction project, both Eurotunnel and Eurostar, companies heavily involved in the Channel Tunnel's construction and operation, have had to resort to large amounts of government aid to deal with debts amounted. Eurotunnel has been described as being in a serious situation.

Incidents

Fires

There have been three fires in the Channel Tunnel that were significant enough to close the tunnel—all on the heavy goods vehicle (HGV) shuttles—and other more minor incidents.

During an "invitation only" testing phase on 9 December 1994, a fire broke out in a Ford Escort car whilst its owner had been loading it on to the upper deck of a tourist shuttle. The fire started at approximately 10:00 with the shuttle train stationary in the Folkestone terminal and was extinguished around 40 minutes later with no passenger injuries.

On 18 November 1996, a fire broke out on a heavy goods vehicle shuttle wagon in the tunnel but nobody was seriously hurt. The exact cause is unknown, although it was not a Eurotunnel equipment or rolling stock problem; it may have been due to arson of a heavy goods vehicle. It is estimated that the heart of the fire reached , with the tunnel severely damaged over , with some affected to some extent. Full operation recommenced six months after the fire.

The tunnel was closed for several hours on 21 August 2006, when a truck on an HGV shuttle train caught fire. On 11 September 2008, a fire occurred in the Channel Tunnel at 13:57 GMT. The incident started on a freight-carrying vehicle train travelling towards France. The event occurred from the French entrance to the tunnel. No one was killed but several people were taken to hospitals suffering from smoke inhalation, and minor cuts and bruises. The tunnel was closed to all traffic, with the undamaged South Tunnel reopening for limited services two days later. Full service resumed on 9 February 2009 after repairs costing €60 million.

Train failures

On the night of 19/20 February 1996, approximately 1,000 passengers became trapped in the Channel Tunnel when two British Rail Class 373 trains on continent-bound Eurostar service broke down owing to failures of electronic circuits caused by snow and ice being deposited and then melting on the circuit boards.

On 3 August 2007, an electrical failure lasting six hours caused passengers to be trapped in the tunnel on a Eurotunnel shuttle crossing.

On the evening of 18 December 2009, during the December 2009 European snowfall, five London-bound trains operating Eurostar services failed inside the tunnel, trapping 2,000 passengers in the tunnel overnight. Five Class 373 trains had departed from Brussels and Paris and encountered cold temperatures in Northern France, the coldest for eight years. A Eurotunnel spokesperson explained that the problem had arisen because of 'fluffy snow' in France, which had evaded the 'winterisation' shields designed to stop snow getting into the electrics. Electrical failure was then caused by the transition from the cold air in France to the warm atmosphere inside the tunnel. One train from Brussels had been turned back before reaching the tunnel; two trains were hauled out of the tunnel using diesel-powered Eurotunnel Class 0001. The blocking of the Channel Tunnel led to the implementation of Operation Stack, the transformation of the M20 motorway into a linear car park.

Snow that had built up on the trains then melted in the heat of the tunnel, the water causing electrical faults. The occasion was the first time during the fifteen years that a Eurostar train had to be evacuated inside the tunnel itself; the failing of four at once being described as "unprecedented". The Channel Tunnel reopened the following morning. Nirj Deva, Member of the European Parliament for South East England, had called for Eurostar chief executive Richard Brown to resign over the incidents. An independent report by Christopher Garnett (former CEO of Great North Eastern Railway) and Claude Gressier (a French transport expert) on the 18/19 December 2009 incidents was issued in February 2010, making 21 recommendations.

A further Class 373 unit on Brussels–London service broke down in the tunnel on 7 January 2010. The train had 236 passengers on board and was towed to Ashford; other trains that had not yet reached the tunnel were turned back.

Asylum and immigration

Immigrants and would-be asylum seekers have been known to use the tunnel to attempt to enter Britain. By 1997, the problem had already attracted international press attention, and the French Red Cross opened a refugee centre at Sangatte in 1999, using a warehouse once used for tunnel construction; by 2002 it housed up to 1500 persons at a time, most of them trying to get to the UK. In 2001, most came from Afghanistan, Iraq and Iran, but African and Eastern European countries are also represented.

Most migrants who got into Britain found some way to ride a freight train, but others used Eurostar. Though the facilities were fenced, airtight security was deemed impossible; refugees would even jump from bridges onto moving trains. In several incidents people were injured during the crossing; others tampered with railway equipment, causing delays and requiring repairs. Eurotunnel said it was losing £5m per month because of the problem. A dozen refugees have died in crossing attempts. Immigrants have also arrived as legitimate Eurostar passengers without proper entry papers.

Local authorities in both France and the UK called for the closure of Sangatte, and Eurotunnel twice sought an injunction against the centre.

In 2002, after the European Commission told France that it was in breach of European Union rules on the free transfer of goods, because of the delays and closures as a result of its poor security, a double fence was built at a cost of £5 million, reducing the numbers of refugees detected each week reaching Britain on goods trains from 250 to almost none. Other measures included CCTV cameras and increased police patrols. At the end of 2002, the Sangatte centre was closed after the UK agreed to take some of its refugees.

Safety

The Channel Tunnel Safety Authority is responsible for some aspects of safety regulation in the tunnel; it reports to the IGC.

The service tunnel is used for access to technical equipment in cross-passages and equipment rooms, to provide fresh-air ventilation, and for emergency evacuation. The Service Tunnel Transport System (STTS) allows fast access to all areas of the tunnel. The service vehicles are rubber-tyred with a buried guidance wire system. Twenty-four STTS vehicles were made, and are used mainly for maintenance but also for firefighting and in emergencies. "Pods" with different purposes, up to a payload of , are inserted into the side of the vehicles. The STTS vehicles cannot turn around within the tunnel, and are driven from either end. The maximum speed is when the steering is locked. A smaller fleet of fifteen Light Service Tunnel Vehicles (LADOGS) were introduced to supplement the STTSs. The LADOGS have a short wheelbase with a turning circle allowing two-point turns within the service tunnel. Steering cannot be locked like the STTS vehicles, and maximum speed is . Pods up to 1 tonne can be loaded onto the rear of the vehicles. Drivers in the tunnel sit on the right, and the vehicles drive on the left. Owing to the risk of French personnel driving on their native right side of the road, sensors in the road vehicles alert the driver if the vehicle strays to the right side of the tunnel.

The three tunnels contain of air that needs to be conditioned for comfort and safety. Air is supplied from ventilation buildings at Shakespeare Cliff and Sangatte, with each building capable of full duty providing 100% standby capacity. Supplementary ventilation also exists on either side of the tunnel. In the event of a fire, ventilation is used to keep smoke out of the service tunnel and move smoke in one direction in the main tunnel to give passengers clean air. The Channel Tunnel was the first mainline railway tunnel to have special cooling equipment. Heat is generated from traction equipment and drag. The design limit was set at , using a mechanical cooling system with refrigeration plants on both the English and French sides that run chilled water circulating in pipes within the tunnel. Piston relief ducts of diameter were chosen to solve the problem, with 4 ducts per kilometre to give close to optimum results. Unfortunately this design led to unacceptable lateral forces on the trains so a reduction in train speed was required and restrictors were installed in the ducts.

The safety issue of a fire on a passenger-vehicle shuttle garnered much attention, with Eurotunnel itself noting that fire was the risk gathering the most attention in a 1994 Safety Case for three reasons: ferry companies opposed to passengers being allowed to remain with their cars; Home Office statistics indicating that car fires had doubled in ten years; and the long length of the tunnel. Eurotunnel commissioned the UK Fire Research Station to give reports of vehicle fires, as well as liaising with Kent Fire Brigade to gather vehicle fire statistics over one year. Fire tests took place at the French Mines Research Establishment with a mock wagon used to investigate how cars burned. The wagon door systems are designed to withstand fire inside the wagon for 30 minutes, longer than the transit time of 27 minutes. Wagon air conditioning units help to purge dangerous fumes from inside the wagon before travel. Each wagon has a fire detection and extinguishing system, with sensing of ions or ultraviolet radiation, smoke and gases that can trigger halon gas to quench a fire. Since the Heavy Goods Vehicle (HGV) wagons are not covered, fire sensors are located on the loading wagon and in the tunnel itself. A water main in the service tunnel provides water to the main tunnels at intervals. The ventilation system can control smoke movement. Special arrival sidings exist to accept a train that is on fire, as the train is not allowed to stop whilst on fire in the tunnel. Eurotunnel has banned a wide range of hazardous goods from travelling in the tunnel. Two STTS vehicles with firefighting pods are on duty at all times, with a maximum delay of 10 minutes before they reach a burning train.

See also

Strait of Gibraltar crossing

British Rail Class 373

Irish Sea tunnel

Japan-Korea Undersea Tunnel

List of Rail megaprojects

Samphire Hoe

Notes

References

External links

The New Inn website

New Plan For Channel Tunnel, May 1929, Popular Mechanics article on a post-WW1 plan for a tunnel that was scrapped by the great depression. A total cost figure of 150 million was given in 1929

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