Sweden's X2000 fleet of tilting trains has been a major catalyst for the renewed interest in this type of technology shown by the newly-privatised British train operators investing in the final years up to the millenium.
Realising that it couldn't build its rail lines as straight as the high-speed lines in the likes of Japan and France, the country's state-controlled infrastructure operator, Banverket, and Swedish state railways (SJ) set about developing a high-speed network designed around tilting train technology in the mid-1980s.
The first X2000 tilting train was delivered from ADtranz in 1990. Since then they have benefited from aggressive marketing, and are credited with saving the Swedish passenger rail network from extinction.
While the initial route chosen for X2000 was the main Stockholm-Gothenburg corridor, infrastructure works have subsequently been carried out over the whole of the country's network to allow all routes to benefit from the success of X2000.
However, it is on this main corridor where the most dramatic time savings have been achieved. In 1990, before the introduction of X2000, journey times averaged three hours 45 minutes. Eight years later, these have been cut by one hour.
The savings in time have also had dramatic effects on SJ's market share of Stockholm-Gothenburg traffic. Ridership increased steadily each year, to reach nearly nine million journeys in 1996, giving it almost 80% of the rail-borne market, and representing a ten-fold increase over the first seven years.
X2000 now has over half of the market for all rail journeys between Sweden's two main cities, and achieved these improvements without the need for lengthy infrastructure works, allowing the benefits to be offered to passengers much more quickly.
Each X2000 formation consists of one 4400hp power car, powered at 15kV ac. Each unit can be made up of up to 16 intermediate vehicles with a maximum capacity of 1,600 passengers, but a typical train will only have five intermediate trailers.
The secondary routes are served by a second generation of X2000, the X2-2.
While the current network is geared for 200km/h (125mph), there are long-term plans for upgrading to allow 300km/h operation.
Each X2000 trainset is mounted on 'soft' bogies, which adjust automatically on curves and mean a train can run up to 40% faster without exerting extra stresses on the track.
An accelerometer measures lateral acceleration on curves and the main computer in the leading vehicle calculates the amount of tilt required and sends instructions to the computer in each coach.
X2000 is fitted with an advanced system of Automatic Train Control (ATC), which provides a series of information about the line up to 4km (two and a half miles) ahead of the driver. If there is no response, the train brakes are automatically applied.
Each train also has three independent braking systems, an electric regenerative brake for speed adjustments down to standstill; air-operated disc brakes for normal and hard braking, and a magnetic track brake for use in emergencies.
Electronic anti-slip devices and parking brakes are also fitted. The standard train brake gives stopping distances of 1.1miles (1,750m) from 200km/h (125mph), 0.75miles (1,100m) from 150km/h (95mph), and 0.4miles (700m) from 130km/h (80mph).
A full emergency application of the magnetic brake will bring the train to a stand from 125mph (200km/h) in 1,100m (0.75miles).
Each X2000 power car has four bogie-mounted asynchronous traction motors grouped in pairs, powering all four axles. The train is powered by single-phase 15,000v 16.7Hz alternating current from the overhead line.
This direct current is converted into alternating current to feed the traction motors, and the transformer also provides 1,000v of direct current to power the trains' heating, batteries and emergency lighting.
The tilting system, ventilation and air conditioning are powered by 380v, three-phase current.
The passenger accommodation is served by a central information system, controlled and updated by the train driver. These give the current time and details of the next station, and are supplemented by announcements over the on-board PA system.
Train drivers are also in communication with signalling and control room staff via SJ's train radio system.
TRACK AND SIGNALLING
In comparison with the cost of the trains, upgrading of infrastructure has been relatively modest, but has represented far better value for money than other countries' high-speed lines which have been built from scratch.
For example, Sweden's upgrading for X2000 worked out at $0.5 million per km, compared with the $9 million per km cost of Spain's AVE high-speed route, and $18 million per km for Germany's ICE network.
The trains' tilting mechanism brings long-term benefits for the track in the form of reduced forces, cutting down on wear, which in turn allows speeds to be increased substantially on straight track, and by up to 50% through curves.
While Sweden has a railway line that is now the envy of many other countries, extension of X2000 operation is only likely to take place on a modest scale, probably using a scaled-down version of the original train to link secondary routes with the high-speed line.
China has followed up its interest in the X2000 project by ordering trains for a service between Guangzhou, Shenzhen and Kowloon, while Britain is also expected to see their introduction on a limited scale when Great North Eastern Railway, a division of Sea Containers, orders a small fleet of X2000 derivatives for its services between London, Yorkshire, the North East and Scotland.