Why destroyed ?

Oil crisis　

In October 1973, members of OPEC proclaimed an oil embargo and it lasted until March 1974. This event is known as 1973 oil crisis and oil prices rose steeply. In such a circumstance, gas turbines were began to be avoided due to their high fuel consumption and high speed rail projects using turbine powered train were all reconsidered.

Advancement in electric drive

　Many advancement were achieved in the field of power electronics which enabled adjustable voltage, adjustable frequency control method. And also advanced technology was established for providing with electricity from an overhead wire. These technologies enabled high speed trains over 300km/h cruising speed with high efficiency.

Delay of the turbine technology revolution

In those days, turbines were thought to be the most revolutionary technology among internal combustion engines. But the revolution was not become real.　High temperature, high flexural strength ceramics were hoped for, but could not be produced in commercial scale and price. High efficient gas turbines were dreams of car industries but could not be realized.

Progress in diesel technology

The diesel technology was advanced slowly but steadily. High volume and mass problems of this engine were gradually reduced. Originally fuel consumption of diesel was low and modern direct injection and electronic technologies improved its efficiency more. Thus, diesels had become the only power source in non-electrified lines and extended their area of activity to a semi-high speed rail. Intercity 125 (HST) was the first non-electrified 200km/h commercial service started in Britain in 1976. 

Thus, any high speed rail was planned upon assumptions that the high speed train's power source was electricity and middle speed diesel.

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