Abstract
The expert research activity of transition zones of tunnels is one part of the overall set of these places on the railway line. Typical places where the stiffness of the railway changes are the portals of tunnels, where undesirable deformations occur during the operation of trainsets due to the changes in materials. In the places of the portals, there can be a ballastless track or slab track (with concrete bearing layer) or classic structure with a railway ballast. The paper presents long-term research on monitoring height changes in these sections. The results of the expert activity will be the basis for the subsequent proposal of new measures, i.e. changes to built-in objects or modification of the materials of structural layers in a given place of the transition zone.