Slab Track, as all railway structures, should provide secure train running and smooth passenger ride. Moreover, it should present sufficient vertical elasticity to distribute the loads to the adjacent fixing points of the rail. At the same time the deflection of the slab track should be comparable to that of the ballasted track which implies a decrease of the value of the acting forces during its Life-Cycle. In this paper the influence of the vertical stiffness of the track on the dimensioning of the slab track as a rigid pavement is presented.