Design of new lines for speeds of 300-350 km/h - State of the art

The construction of new high speed railway lines is currently being undertaken in a large number of countries, in particular on the continent of Europe. There are now more than 2 900 km open for commercial service in Europe (and more than 2 000 km under construction) as well as almost 2 200 km in Japan.
The development of these new lines has been done over a period of more than forty years, between the middle of the 1950s and the current decade. During this period the design criteria have been modified as experience has been gained with the different aspects of high speed running.
In particular, the geometric parameters of the route chosen in the new infrastructure projects for a certain design speed, in fact, permit higher maximum speeds than those specified when the line was opened (which were chosen depending on the technical, commercial and economic criteria).
Experience shows that the design engineers like to keep a certain "reserve of speed" for the future. The different life expectancy of the infrastructure and rolling stock suggests that this reserve should be respected but competition obliges it to be reduced.
Figure 1 shows the increase of maximum speeds in experimental test runs and in commercial service during the last few decades. Figure 2 gives the total number of kilometres of test runs done by SNCF, in the range of speeds between 400 and 515 km/h.