The magnificent powertrains called for new developments in track design To achieve amazing speeds. Train Grande Vitesse (TGV) tracks, welded rails on hybrid steel and concrete ties, lay on a thick bed of ballast. The combination of curve radii and super-elevation makes high speed possible: a 5 km (3 mile) radius would be considered tight. Instead of each car with its own wheels, they are semi-permanently attached on a two-axle truck between them. The Maglev is a system in which the train runs levitated from the tracks by using electromagnetic forces between superconducting magnets on board the vehicle and coils on the ground. When the magnets pass at high speed, an electric current is induced within the coils, which then act as electromagnets temporarily. As a result, there are forces which push the superconducting magnet upwards and ones which pull them upwards simultaneously, thereby levitating the Maglev. The repulsive force and the attractive force induced between the magnets propel the Maglev forward at great speed.