So-called “non-load bearing” parts of (railway) bridges increase the stiffness and decrease the stresses in short span bridge structures. The rail track, consisting of ballast, sleepers and rails, has a non-linear behaviour and its rigidity depends on the vertical load. By means of analytical investigations, the influence of parameters such as the reinforcement content, the load configuration and the load amplitude on the fatigue stress in the steel reinforcement of the concrete bridge structure is obtained. The results show a 5 – 8 % reduction of the fatigue stress when considering this interaction as compared to conventional structural analyses not considering the load bearing contribution of the rail track. The benefits of this methodology is in view of examining concrete railway bridges for heavier future traffic loads. Since shear failure is unlikely to occur in common bridge elements such as decks and girders, emphasis is given on the determination of stresses due to bending moments.