INTRODUCTION the railway infrastructure Administration, as well as any other organism that is trustworthy for the supervision of the railway system, is responsible for the construction of the most innovating infrastructures, than usually they are financed by the Government, as well as the service load of maintenance throughout all the railway system so that they are in the state adapted for its use as much for the conventional trains as those of high speed, as well as the calls " of carga" used essentially for marine transport services. This task cannot be realised if the Administration or organism at issue are not equipped with sufficient technological resources so that it can choose to certify and to validate to his suppliers and thus to equip to the infrastructure of the necessary quality for a so delicate and strategic sector as the railroader. The multiplication of the speeds reached about the trains that are at this moment operative has given rise to an important multiplication of the dynamic tensions that tracks and all the elements of anchorage must resist. Therefore, the purchase of any material, equipment or system it will have to be put under demanding tests, that they are carried out in order to verify that they are adapted and to confirm that they fulfill all the requirements that are demanded. In view of the fact that the components are not standard and vary much from a supplier to another one, not only in his form but also that in his composition (metals, polymers, ceramic and composed), he is essential to carry out independent tests in each of them, as well as tests as a whole, in order to assure that they respond to all the elements suitably that interact to each other. Nowadays, the fact that the provided materials are solid and resistant it is not sufficient, but also they are forced to provide to the passengers a greater comfort FATIGUE TESTS IN WELDS OF MEETINGS OF HIGH SPEED IN ROUTES FERRAS Hay a series of differences between habitual welds and the welds that are used in the routes of the railroad: composition, the types of tension to that they are put under, the processes of weld, etc These detailed characteristics will force to realise the exact mechanical tests to make sure that the weld process is correct and that the mechanical properties of the joint are adapted.