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Wednesday, 24 April, 2002, 13:26 GMT 14:26 UK
Light at the end of the tunnel
The caverns at Laerdal simulate 'dawn'
A survey by Europe's leading motoring organisations says two of Britain's busiest road tunnels are among the least safe in Europe. BBC News Online's Chris Summers investigates how design has moved on since the construction of the Blackwall tunnel.

When the first Blackwall tunnel was built in 1897 it was designed for horse-drawn carts and carriages.

It had to be curved, rather than straight, simply because the horses would bolt if they saw the light at the end of the tunnel.

Road tunnels worldwide
Laerdal, Norway (24.5km)
St Gotthard, Switzerland (16.9km)
Mont Blanc, France/Italy (11.6km)
Mersey Queensway, UK (3.6km)
Salang, Afghanistan (2.5km)
Blackwall northbound, UK (1.3km)
Nowadays horses and carts have been replaced by cars and lorries.

In Victorian times a collision was unlikely to be fatal, but the consequences of a modern road tunnel accident can be horrific.

Eleven people lost their lives in October 2001 when two lorries collided head-on in the St Gotthard tunnel in Switzerland.

One of the trucks was carrying tyres, which ignited and burned for several days, filling the tunnel with acrid black smoke.

In 1999 a crash, followed by a fire, in the Mont Blanc tunnel between France and Italy killed 39 people.

Tiredness 'is a factor'

It is often impossible for accident investigators to discover the initial reason for these crashes.

But one contributory cause, in many cases, is believed to be tiredness or disorientation which causes a driver to crash into either another vehicle or the tunnel wall.

St Gotthard tunnel fire
The St Gotthard tunnel fire killed 11 people

This is particularly prevalent in long tunnels such as the St Gotthard (16.9km) and the Mont Blanc (11.6km), where monotony begins to play a role.

So when the Norwegian authorities began planning for the 24.5km Laerdal tunnel, which would become the world's longest, safety was very much in their thoughts.

The tunnel is on the main Bergen-Oslo road but carries only a fraction of the traffic of the big Alpine tunnels.

World expert

Nevertheless up to 400 lorries pass through it every day and its safety record is impressive - with only one minor accident in the 18 months since it opened.

Gunnar Lotsberg, who helped design Laerdal, is one of the world's foremost authorities on road tunnel design and next month he will be in Afghanistan looking at ways of refurbishing the Salang tunnel, which was devastated by war.

Laerdal map
He recruited psychologist and behavioural scientist Gunnar Jenssen, from the University of Trondheim, to find out what could be done to make the 20 minute journey through the tunnel less tedious and therefore safer.

Mr Lotsberg told BBC News Online: "The journey from Bergen or Oslo to the tunnel takes 3-4 hours and if there is a lot of snow it can take longer.

"The danger is that the drivers feel relieved when they get into the tunnel and tend to fall asleep."

"If the spacing between the tunnel lights matches the resting rhythm of the heart it can induce a hypnotic effect," said Mr Jenssen, who said one of the volunteers actually fell asleep while on a particularly monotonous simulator.

If the spacing between the tunnel lights matches the resting rhythm of the heart it can induce a hypnotic effect,

Gunnar Jenssen, behavioural scientist
Mr Jenssen suggested a number of ideas and conducted tests and computer simulations on volunteers to find out which worked best.

As a result Laerdal was built in four sections with three caverns or "mountain halls" in between.

"Because it was in sections, people did not feel that it was so long," said Mr Lotsberg.

Each cavern has also been built with special lighting - yellow at the bottom and blue at the top - which is designed to simulate the sunrise.

The driver simulator tests suggested these "dawns" refreshed the drivers as they passed through the caverns.

Motorists are also able to do a U-turn at each of the mountain halls if, for example they are running low on fuel.

The caverns also have laybys to allow drivers to pull over and have a rest.

The tunnel is also fitted with a state-of-the-art ventilation system and there are 15 special signal boosters which allow mobile phones to work inside it.

Blackwall Tunnel
Blackwall Tunnel was rated 'very poor' in the survey
Staff in a control room monitor pollution levels in the tunnel and if an accident occurs fans swing into action to suck the smoke up a 2km chimney.

Role model

Laerdal is now seen as the role model for tunnel designers worldwide.

It was visited recently by a group of Chinese engineers who are constructing an 18km tunnel at Zhongnanshan.

Mr Jenssen said Blackwall and some of Britain's tunnels could benefit from some of their ideas but he said: "In high density city tunnels there are other problems, such as disorientation.

"The accident risk at the tunnel entrance is five times higher than in the middle because drivers have difficulty adjusting, especially in daylight," he said.

Peter Heather, director of operations at Transport for London, said a 15m refurbishment of the Blackwall southbound tunnel had already started.

He said it would introduce new technology which would allow mobile phones and car radios to work underground.

It would also enable the control room to interrupt car radio frequencies with emergency messages.

See also:

30 Oct 01 | Europe
New crash hits Swiss tunnels
26 Apr 00 | UK
Tyne tunnel safety slated
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