Currently one of the most actual transportation problems in Saint Petersburg is the insufficient stability of pavement in conditions of high humidity. Strengthening the road embankments is able to solve this problem and increase the service life of the whole structure. So that, an optimal choice of necessary method of protection is an important task. The purpose is to study different methods of strengthening, to consider the specific technical characteristics of each of them and finally, to find the optimal one. The study showed review of the main methods to support subgrade slopes of existing roads. The schemes of used structures are demonstrated. Geodesic measurements of vertical precipitation were carried out on one of the sections of the federal highway "Scandinavia". Based on the calculations, diagrams were constructed and the most reliable method is identified.