High-speed rail (HSR) is a type of passenger railroad that operates much faster than normal railroad speeds. Specific European Union definitions include 200 km/h (120 mph) for an upgraded track and 250 km/h (160 mph) or faster for a new track.
In Japan, Shinkansen lines travel at speeds in excess of 260 km/h (160 mph) and are built using standard gauge without ground level crossings. In China, high-speed conventional rail lines operate at a maximum speed of 350 km/h (220 mph). The world record for conventional high-speed railroads belongs to the V150, a specially configured version of Alstom’s TGV, which reached 574.8 km/h (357.2 miles per hour) on a test run.
A number of different definitions of high-speed railroads are used around the world, there is no single standard, but there are certain parameters that are unique to high-speed railroads. The UIC (International Union of Railways) and EU Directive 96/58 define high-speed rail as a system of rolling stock and infrastructure that regularly operates at 250 km/h or higher on new tracks or 200 km/h on existing tracks. However, lower speeds may be required due to local constraints. A defining aspect of high-speed railroads is the use of continuous welded rails, which reduce track vibrations and mismatches between rail segments sufficiently to allow trains to travel at speeds in excess of 200 km/h (120 mph). Depending on design speed, roll and passenger allowable forces, curve radii exceed 4.5 km, and for lines capable of 350 km/h, usually 7 to 9 km. There are also a number of features common to most high-speed rail systems, but not required: almost all are electrically driven overhead lines and have in-cab signaling and no rail crossings. Advanced switches with very low entry angles and crossheads are also often used.
Technologies
KTX-Sancheon, the South Korean high-speed train at Seoul Station. Much of the technology behind high-speed rail is an improved application of mature standard-gauge railroad technology using aerial electrification. By building new rail infrastructure with 20th century engineering, including the elimination of constraints such as grade (level) crossings, frequent stops, sequences of curves and reversals, and the elimination of lane separation with freight or slower passenger trains maintaining higher speeds (250-320 km/h). The total cost of ownership of HSR systems is generally lower than the total cost of competing alternatives (new highway or capacity). Japanese systems are often more expensive than their counterparts, but are more versatile because they have their own dedicated overhead guideway, no traffic crossings, and disaster monitoring systems.