Road slopes stability is a prerequisite for the safety of engineering constructions or natural slopes. It is especially important for road traffic safety, preservation of life and the environment. Physio-mechanical properties of geomedia are very important for the stability and general geotechnical condition of a slope. Preliminary research using seismic methods provides qualitative and quantitative insight into the intensity and location of changes in engineering parameters and properties of geomedia, soil and rocks. Refractive tomography and multichannel analysis of surface waves are used to determine seismic velocities as geophysical parameters from which it is possible to determine dynamic properties and quality index or the degree of disintegration of geomedia in the body of a slope. The results of these research studies, apart from assessing the condition, are also used as a basis for designing interventions and protection measures, i.e. increasing the stability of road slopes. A geophysical preliminary seismic survey was performed on the state road DC1, section 16 Vrlika – Satrić, to assess the condition of road slopes. The aim of the research is to enable a quality preparation of a project design for the rehabilitation of potentially unstable slopes.