Desire for higher speed !

　As a prime mover for locomotive, only in the U.S. gas turbines engaged in large scale commercial use, but in 60's the demand for high speed rail increased the significance of  the gas turbine's high power.

Impact of Shinkansen

Success of the bullet train "Shinkansen" astonished rail industries all over the world. 

In those days rail industry was on the road of decline and extinction because people took a long distance trip by air and short trip by car, many believed the supremacy of automobiles and planes. Shinkansen was being build in these circumstances.
As is well known, its success applied the brakes to declining of a rail transportation and gave the hope to railroad industries for high speed rail.

Not new track

Conventional tracks in Europe and America had straight or shallowly curved track without steep slope and conventional trains had been operating at 160 km/h. So conventional lines were used for high speed operation in these countries to avoid high capital cost for the construction of new lines. A high speed non-electrified train was also expected to avoid high capital cost for electrifications.

Advancement of gas turbines

In those days the power source of airplanes are occupied by gas turbines and the turbine performance was nothing short of amazing. Many engineers were eager to apply this turbine performance to land and sea applications.

There were many projects to utilize turbines to automotive power source, in the Indy 500 reciprocating engine cars were feared by a turbine car.
In railroads even electric trains had not enough performance and steams and diesels were far from the high speed.

Limits of electric drive

In those days, electric motors had comparably enough performance to achieve over 200km/h speed. Shinkansen's maximum operating speed was 210km/h from the first commercial operation and 256km/h at the speed trial.
In French, the electric locomotive achieved 330.88km/h in 1955. 

This is the record of one time speed trial and tracks and catenaries were severely damaged at this trial and engineers knew difficulties of providing with electricity from an overhead wire.
There were no other speed trial over 300km/h except this.　　

Limits of diesel drive

Diesels were left behind of steams in the performance and in 1936, German high speed DMU achieved the record of 205km/h. 3 years after, the new record was established (215km/h).
Steams were exceeded 200km/h already and in 1938 British Mallard established the record 202.8km/h.
After this period, the speed record of diesels had not advanced until British HST achieved 229km/h.

This very slow improvement did not made rail engineers expect the high speed application of the diesel train and they expected the high performance of a gas turbine to build non-electric high speed lines.