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DEBATE - Road tunnels

DEBATE: Urban tunnelling is back on the agenda as a simple and cost effective way to beat traffic chaos in Britain's cities. This week we ask: Are road tunnels the best way to beat traffic congestion in urban areas?

Yes Ruth Bridger, project manager, AA motoring policy unit

In countries across the world, urban road tunnels are being constructed not only to relieve traffic congestion but also to provide a better environment above ground. City suburbs are reunited as new tunnels, taking through traffic underground, allow the surface streets to be reclaimed for the benefit of pedestrians, cyclists, emergency services and public transport passengers.

In real terms, the cost of tunnel construction is falling by about 4% each year. Urban tunnels can be cheaper than surface building where acquiring land or moving utilities is expensive.

In Paris, where a surface road option would have threatened a region rich in natural and historic sites, an innovative tunnelling solution is now in the construction phase. The dual three lane carriageway of the A86 Versailles tunnel, reserved for light vehicles only, can now complete the Paris outer ring road without any threat to historic and residential areas. This project is privately funded and will be financed by tolls, collected electronically.

With the current generation of petrol cars producing around 67% of the toxic urban pollution of their non-catalytic converter forerunners, tunnel ventilation problems are simplified. And replacing the stop-go traffic on the surface with free flow movement in tunnels reduces the overall emissions from the same volume of traffic. In Boston, carbon monoxide is forecast to drop by 12% across the city when the 128km of traffic lanes under construction in tunnel are fully operational.

No-one should contemplate a tunnel option lightly or think any environment can justify the cost.

But from Boston to Paris and Salzburg to Sydney, forwardthinking city planners have taken the underground option to relieve traffic congestion in urban areas. Perhaps it is time for UK politicians and planners to take urban tunnelling more seriously.

No Lynn Sloman, assistant director, Transport 2000

Tunnels are a phenomenally expensive way to tackle traffic problems in cities. For example, the 'Big Dig' project to build a tunnel under Boston in the US was forecast to cost a massive $12.2bn (£8.1bn) and is now running well over budget.

Because of their enormous cost, tunnels are not a serious option to replace more than a few kilometres of urban highway. And a fraction of the billions of pounds needed for just a short stretch of urban tunnel could transform the quality of public transport, paying for light rail networks, high quality buses, more frequent rail and bus services, safe cycle routes, safe routes to schools, traffic calming, home zones, and much lower fares.

Together, these could dramatically cut traffic in cities.

Some tunnel enthusiasts say costs can be cut by only allowing cars and vans underground. If lorries are banned, tunnels can be smaller and will require less maintenance, they argue. This is the thinking for the 10km Versailles tunnel west of Paris. But if residents still suffer heavy trucks thundering past their doors, a tunnel is of little or no environmental benefit.

And how much car traffic will an urban tunnel take off the roads anyway? Most journeys in urban areas are very short. Tunnels only work for through traffic - it is hard to build complex junctions underground - so they only take a small proportion of traffic off urban streets, with little impact on noise, pollution, danger and severance at street level.

Like motorway widening, the main effect of tunnels is to increase highway capacity, which in turn increases traffic.

Where the tunnel ends, that traffic is disgorged into already busy streets. Unlike investment in public transport, tunnels do not get cars and lorries off the road.

They are a grossly expensive and ineffective pipe dream.

The facts In June the AA launched a report called Going Underground which looks at the role of tunnels in town and country. For a copy of the report contact motorist@theaa. com The report says that road tunnelling projects have regained popularity worldwide with recent projects in Paris, Lyon, Marsellies, Brussels, Madrid and Sydney.

It claims that the cost of road tunnels is coming down by about 4% a year to around £50M per km now. It is said to be cheaper than surface building where acquiring land or moving utilities is expensive.

Congestion busting efforts in UK cities are focused on plans to charge drivers to enter towns and cities and to charge them for parking at work. Over 20 local authorities have expressed interest in developing schemes.

London is expected to be the first to have a congestion charging scheme in 2003.

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