Roller devices have been a switch equipment standard at European railway companies for many years. For switches in the closed condition, the switch rail ideally lies against the stock rail in the front area of the switch and against the stop blocks in the heel. In switches within the superelevation it may be that the switch rail is no longer in the optimal position against the stop blocks. An undesirable constriction of the track gauge might then occur.
However, lengthy operational use, i.e. repeated  load application on the switch rail in the heel area by passing trains, also causes the specified or pre-curved shape of the switch rail to change in the longitudinal and transverse rail direction.