1. Existing High Speed Networks

High speed trains refer to passenger rail systems running at operational speed between 200 and 300 km/h. They have been developed in Japan, France, Germany, Spain and South Korea. Another high speed system in Taiwan, linking Taipei to Kaohsiung, is scheduled to be completed in 2006. The high speed train passenger system era truly originates from Japan with the Tokaido line, bridging Tokyo and Osaka, which began in 1964 with the Tokyo Olympics. Today, this transport mode is perceived as an efficient alternative to highway and airport congestion. Evidence underline that travel time are cut in about a half when a high speed service begins. High speed trains currently function under two discrete technologies.

• Improvement of conventional rail. The first type uses existing conventional rail systems and its great velocity is primarily the fact of considerable improvements in locomotive performance and train design. They may not be considered as a high speed trains per se. England (London - Edinburgh), Sweden (Stockholm - Gothenburg), Italy (Rome - Florence and Rome - Milan), and the United-States (Boston - Washington) are examples of this type of technology. Trains can reach peak speeds of approximately 200 km/h in most cases and up to 250 km/h in Italy. The principal drawback from using this system, however, is that it must share existing lines with regular freight services.
• Exclusive high speed networks. In contrast, the second category of high speed trains runs on its own exclusive and independent tracks. Such systems are presently in operation in France, Spain, Germany, Japan and South Korea. In Japan, trains can attain speeds of 240 km/h, but ongoing projects to raise peak speeds at 300 km/h aim at maintaining competitiveness of rail passenger transport versus air. In France, the TGV Sud-Est (Trains a grande vitesse) reach speeds of 270 km/h while the TGV Atlantique can cruise at speeds of 300 km/h. One of the key advantages of such a system is since passengers trains have their exclusive tracks, the efficiency of rail freight transport increases as it inherit the almost exclusive use of the conventional rail system.

The setting of high speed train networks consequently must take into consideration the following constraints:

• Distance between stations.
• Separation from other rail systems.
• Availability of land, both for terminals and high speed lines.

2. New Technologies

In addition to present technologies, an entirely new technological paradigm has been under development in Japan and Germany since the late 1970s. The new technology is known as Maglev (Magnetic Levitation); it utilizes magnetic forces to uplift trains, guide them laterally and to propel them, relying upon highly efficient electromagnetic systems. The first commercial maglev rail system was inaugurated in Shanghai in 2003. Maglev systems have experienced some constraints on widespread commercialization, however, such as difficulties with integration in established rail corridors and perceptions of high construction costs.