Punktförmige Zugbeeinflussung
After acknowledging the warning signal the train has to stay below the braking curve (German "Bremskurve") - fast trains may travel up to 165 km/h and they must reduce the speed to below 85 km/h after 23 seconds. Note that the operation of high speed trains beyond 165 km/h is not based on visual wayside signals or PZB inductors (using LZB or European Train Control System cab-signalling instead in Germany).
High-speed rail in Europe
Britain has a history of high-speed rail, starting with early high-speed steam systems: examples of engines are GWR 3700 Class 3440 City of Truro and the steam-record holder LNER Class A4 4468 Mallard. Later, high-speed diesel and electric services were introduced, using upgraded main lines, mainly the Great Western Main Line (GWML) and East Coast Mainline.
The InterCity 125, otherwise known as the "High-Speed Train" (HST), was launched in 1976 with a service speed of and provided the first high-speed rail services in Britain. The HST was diesel-powered, and the GWML was the first to be modified for the new service. Because the GWML had been built mostly straight, often with four tracks and with a distance of 1 mile (about 1.6 km) between distant signal and main signal, it allowed trains to run at with relatively moderate infrastructure investments, compared to other countries in Europe. The Intercity 125 had proven the economic case for high-speed rail, and British Rail was keen to explore further advances.