Changes in railway unevenness after the installation of in-track vibration countermeasures

When in-track vibration countermeasures, such as resilient rail and slab support are installed, the unevenness perceived by a train will be modified and this is often not accounted for. In this paper, it is investigated, with the aid of an analytical track model, how this perceived unevenness will change and what the relation is with different types of unevenness for the particular case of a floating slab track. The different types of unevenness considered are: track bed unevenness, bent rail, bent slab and variation of slab bending stiffness. The total unevenness perceived by the wheels of a moving train is the result of a combination of these and other types of unevenness. It is found that, depending on the unevenness type, both a reduction or an increase of the perceived unevenness are possible. The increase may be large enough to lead to a substantial reduction in the performance of the vibration countermeasure.