High-speed rail
High-speed rail is a type of rail transport that operates significantly faster than traditional rail traffic, using an integrated system of specialized rolling stock and dedicated tracks. While there is no single standard that applies worldwide, new lines in excess of and existing lines in excess of are widely considered to be high-speed, with some extending the definition to include lower speeds in areas for which these speeds still represent significant improvements. The first such system began operations in Japan in 1964 and was widely known as the bullet train. High-speed trains normally operate on standard gauge tracks of continuously welded rail on grade-separated right-of-way that incorporates a large turning radius in its design.
High-speed rail in the United Kingdom
Despite advances in locomotive engineering, the railway infrastructure was unable to support safe running at such high speeds and, until the mid-1970s, the British railway speed limit remained at .
In the 1970s, British Rail began to explore new technologies for enabling high-speed passenger rail services in the UK. While the Japanese and French railway authorities had decided to build completely new tracks for their respective Shinkansen and TGV high-speed rail systems, British Rail opted instead to develop a train capable of running on existing rail infrastructure: the "Advanced Passenger Train (APT)", with a top speed of . An experimental version, the "APT-E" was tested between 1972 and 1976. It was equipped with a tilting mechanism which allowed the train to tilt into bends to reduce cornering forces on passengers, and was powered by gas turbines (the first to be used on British Rail since the Great Western Railway, and subsequent Western Region utilised Swiss built Brown-Boveri, and British built Metropolitan Vickers locomotives (18000 and 18100) in the early 1950s). The 1970s oil crisis prompted a rethink in the choice of motive power (as with the prototype TGV in France), and British Rail later opted for traditional electric overhead lines when the pre-production and production APTs were brought into service in 1980-86.