High-speed rail is a type of rail transport that operates significantly faster than traditional rail traffic, using an integrated system of specialized
Many countries have developed high-speed rail to connect major cities, including Austria, Belgium, China, Finland, France, Germany, Ireland, Italy, Japan, Morocco, the Netherlands, Poland, Portugal, Russia, Saudi Arabia, South Korea, Spain, Sweden, Taiwan, Turkey, the United Kingdom, the United States, and Uzbekistan. Only in Europe does HSR cross international borders. China has 22,000 kilometres (14,000 mi) of HSR as of end December 2016, accounting for two-thirds of the world's total.
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Multiple definitions for high-speed rail are in use worldwide.
A third definition of high-speed and very high-speed rail (Demiridis & Pyrgidis 2012) requires simultaneous fulfilment of the following two conditions:
The UIC prefers to use "definitions" (plural) because they consider that there is no single standard definition of high-speed rail, nor even standard usage of the terms ("high speed", or "very high speed"). They make use of the European EC Directive 96/48, stating that high speed is a combination of all the elements which constitute the system: infrastructure, rolling stock and operating conditions.
The criterion of 200 kilometres per hour (120 mph) is selected for several reasons; above this speed, the impacts of geometric defects are intensified, track adhesion is decreased, aerodynamic resistance is greatly increased, pressure fluctuations within tunnels cause passenger discomfort, and it becomes difficult for drivers to identify trackside signalling. Standard signaling equipment is often limited to speeds below 200 km/h with the traditional limits of 79 mph (127 km/h) in the US, 160 km/h (99 mph) in Germany and 125 mph (201 km/h) in Britain. Above those speeds
National domestic standards may vary from the international ones.