General definitions of highspeed
We have deliberately used the word “definition” in the plural because there is no single standard definition of high speed rail (nor even a standard usage of the term: sometimes it is called “high speed” and sometimes “very high speed”). The definitions vary according to the criteria used since high speed rail corresponds to a complex reality. We on the UIC High Speed Taskforce wanted to reflect this diversity by considering high speed from all the standpoints: infrastructure, rolling stock and operating.
First of all there is the European Union definition, given in Directive 96/48; this is a fairly broad definition which encompasses a large number of systems under the banner of high speed.
But it is also necessary to take into account those railways which are making laudable efforts to provide high speed despite a basis of old infrastructure and technology which is far removed from that employed by the railways of western Europe.
At all events, high speed is a combination of all the elements which constitute the “system”: infrastructure (new lines designed for speeds above 250 km/h and upgraded lines for speeds up to 200 or even 220 km/h, some worked with tilting trains, some not), rolling stock and operating conditions. In view of the fact that many high speed trains are also compatible with the conventional network, the term “high speed traffic” is also frequently understood to signify the movements of this type of train on conventional lines but at speeds lower than those permitted on the new high speed infrastructure. Consequently, on some lines which are claimed to be high speed lines it is very difficult to specify a threshold when, in certain very densely populated regions, the speed is restricted to 110 km/h in order to avoid noise nuisance, or where, as in special tunnel sections or on long bridges, the speed is limited to 160 or 180 km/h for obvious reasons associated with capacity or safety. Finally, in many countries where the performance of the conventional railway is not very high, the introduction of some trains capable of operating at 160 km/h and offering a significant level of quality - often as a first step towards a future genuinely high speed service - may already be considered as high speed.
