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The fast track approach

The new generation of ultra-fast trains is much more likely to run on concrete slabtrack than traditional sleepers and ballast. David Jones explains why.

Concrete slabtrack comes in many versions, both slipformed and precast. Most of the ultra-fast trains being introduced in many parts of the world will be running on concrete slabtrack rather than traditional ballast. There are very good reasons for this choice, not least increased safety and reliability and much reduced maintenance.

Accurate track geometry can be achieved with concrete slabtrack systems: this produces a smooth ride for passengers and less wear and tear on train suspension systems. Most importantly, in the wake of the Hatfield disaster, rail breaks are rare and much less likely to be catastrophic if they happen on concrete slabtrack. And the concrete slab is lighter and shallower than the equivalent ballast bed.

With its fleet of ultra-fast bullet trains, known as Shinkansen, Japan was the first country to develop a network of track built using a combination of slipformed and precast concrete.

Japan now has more than 25 years' experience operating high-speed trains on concrete slabtracks. Their maintenance, safety and productivity records show they are world leaders.

For example, comparative productivity figures based on tonnes of freight, passengers, kilometres of track and employees show that the Japanese railways are more than three times more productive than those in the UK. The benefits that come from a reduction in unplanned maintenance can be seen from a reliability comparison.

In October 1999 on Virgin's Euston/Scotland route, only 76.3% of trains arrived within 10 minutes of the timetable. This is in contrast to the Tokaido Shinkansen in Japan where 96.1% of trains travelling over a similar distance - for example on the Tokyo to Osaka route - arrived exactly on time and only 0.8% were 10 minutes or more late.

Despite the successful use of slabtrack in Japan the French opted for traditional ballast when the high speed TGV network was developed. And it has managed to make it work - but at a cost.

Ballast breaks down under the vibration of high-speed trains, and on some lines is replaced and repacked every night. Pieces of ballast are often sucked up and deposited on the rails, causing damage to the next train.

Recognising the problems with the TGV system, Britpave member, Alstom, is developing a version of its Appitrack (slabtrack) system. (see box) But it is the Germans - soon to be followed by the Dutch - who are the European leaders in building a new generation railway system.

Deutsche Bahn is pressing ahead with plans to provide 6,000km of rigid trackbed for its high-speed lines. Several different versions are being used with, as yet, no clear overall winning design.

Construction is well under way on the new Frankfurt/ Cologne high-speed link, along which trains will travel at 300km/h. Four slipform pavers, using a proprietary Leica guidance system, are working on the project (see box). Britpave will be offering a visit to this exciting contract later this year.

In the Netherlands too, a major high-speed route is out to tender, and construction is due to start this spring. Known as the North/South route, it runs from Amsterdam to the Belgian border and will be a concrete slabtrack system.

Slabtrack is not new to the UK: in British Rail's time, concrete was used extensively in tunnels. Recently, short stretches of rigid trackbed have been used on the Heathrow Express, Stansted Airport links and at the Eurostar terminal.

Initial cost has always been given as the reason why concrete slabtrack has not been widely used in this country. The initial cost of slabtrack is 1.3 to 1.5 times that of conventional track, but maintenance costs are dramatically reduced. Now the debate on safety and maintenance has come out into the open, this old initial cost mindset could be about to change.

Concrete slabtrack is most competitive when building highspeed new lines. Its use gives designers significant engineering benefits by reducing deadweight over bridges and viaducts, and in saving headroom in tunnels. Other opportunities for slabtrack are in loop lines, crossovers and heavy freight lines. With safety so high on the agenda, slabtrack could be used in high-risk areas such as curves, or where rail breaks have been a severe problem.

Slabtrack designs are now well tested. We just need the opportunity in the UK to show how modern concrete solutions can help us build a world-class, fast, safe railway system. At the Britpave seminar in October, Andy Doherty, Railtrack's director of asset management, pledged a 15km trial of slabtrack in the near future. That was immediately before Hatfield, and Britpave is continuing to press Railtrack to bring this forward.

David Jones is director of Britpave

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