High Speed Rail

High-speed rail is a type of passenger rail transport that operates significantly faster than the normal speed of rail traffic. Specific definitions include 200-320 km/h (125-200 mph) - depending on whether the track is upgraded or new - by the European Union and above 90 mph (145 km/h) by the  United States Federal Railroad Administration, but there is no single standard, and lower speeds can be required by local constraints.
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A rail transportation system with exclusive right-of-way which serves densely traveled corridors at speeds of 124 miles per hour and greater. (APTA1)

A rail service having the characteristics of intercity rail service which operates primarily on a dedicated guideway or track not used, for the most part, by freight, including, but not limited to, trains on welded rail, magnetically levitated (MAGLEV) vehicles on a special guideway, or other advanced technology vehicles, designed to travel at speeds in excess of those possible on other types of railroads. (49CFR37)