Thus, the "high speed system" concept can prove difficult to define, insofar as each infrastructure manager or train operator has his own interpretation of it. For the time being it is not possible to harmonise the viewpoints of the various railway parties involved. One of the most tangible consequences of this is the difficulty of compiling statistics relating to high speed and drawing up high speed network maps
It is possible to outline four types of high speed system:
- CASE N°1
- Type 1 is the most classic and the "purest" high speed system. This constitutes a network of lines used exclusively by high speed trains which themselves do not operate on any other lines. The Japanese Shinkansen systems are such systems.
- CASE N°2
- Type 2 is a network of high speed lines, again used exclusively by high speed trains, but the trains in question also run on conventional lines. In the case of France, high speed trains benefits from classic network to extend their advantages to al the French geography.
- CASE N°3
- The Spanish system (AVE) constitutes type 3, i.e. a system of high speed lines which are used not only by high speed trains (> 250 km/h) but also by some conventional trains equiped of changing gauge systems, at lower speeds - which invariably involves capacity reductions. On the other hand, high speed trains do not run on conventional lines.
- CASE N°4
- The German and Italian systems are examples of type 4 which permitts all types of train run on the high speed lines and the high speed trains run on all types of lines.
As a rule high speed traffic will be calculated from the infrastructure standpoint; in certain cases, however, limits will be set, e.g. a minimum speed of 160 km/h or a count of the number of long-distance daytime services.
Finally, in the case of running through mountain tunnels or crossing long bridges, where the nominal speeds will not be more than 160 to 180 km/h, only high speed trains are considered.
High speed is invariably associated with quality service. And it sometimes happens that a service offering a high level of comfort, frequency and accessibility, even when not accompanied by very high speed, is still labelled high speed. This applies in particular in the case of express link services between cities and their airports over distances of the order of 50 km, operated at about 15 minute intervals and at speeds of up to 200 km/h.
It is also the case where railway services are used as a substitute for air services between airports, and which provide facilities typical of air services (on-board staff, flight numbers, embarkation cards, etc.).
This is always the case with trains reserved for senior executives, access to which is filtered on the platform (thus obviating the need for at-seat ticket inspections), where passengers can work in congenial conditions (space for meetings - possibly adaptable, sockets for PCs, and soon also fax machines, printers and internet connections, etc.) and can order taxis in the train.
Although on some networks freight trains are allowed to run on the high speed lines they are severely restricted and at present operate only at night.
A final facet of high speed rail is the high speed freight service; at present, however, this is virtually non-existent (except for mail trains), but it is likely to be developed in the near future.
An essential feature, in addition to the different types of "speed" envisaged (maximum trial speed, maximum operating speed, average speed, commercial speed, etc.), is the concept of the facilities provided, not only on board the train but throughout the whole journey from door to door. For this reason it is worth while adopting the term "high performance train".