The basic task of the work was to conduct the research aimed at studying the technical condition of the track and its impact on the rolling stock since the car dynamics, especially in curves and on the mountain pass sections of the track, is completely dependent on track deviations. The real time data received from specialized car laboratories show the existence of deviations visually detected, however external deviations are not crucial since the main problem lies inside the structure with changes already taking place in the layers of the subgrade not reflected externally, still affecting the movement of the rolling stock, especially the cars already having permissible technical deviations in operation. The technical condition of the track is directly related to the subgrade and ballast layer therefore the research is aimed at studying the lower base of the track in order to identify defects and malfunctions limiting the speed of the rolling stock and posing a constant threat to the safety of the transportation process. The main task is to identify and study the technical deviation of the subgrade layers, which directly affects the safety of the rolling stock, especially with an increase in freight traffic. The article proposes a method for evaluating GPR sounding of the subgrade, which sees into the depth of the soil up to 8 meters, depending on the equipment used. A theoretical study of the influence of the subgrade on the derailment of the rolling stock due to the deformation of the rail-sleeper grid allows to find the cause of deviations in the dynamics of the car when passing through the corresponding section. This article contains a quantitative and qualitative analysis obtained as a result of a research based on which comprehensive measures were developed to ensure traffic safety. At present, the operation of railways requires increased safety, an increase in the speed of rolling stock and the throughput of the main railway network. With regular inspections at the wagon laboratories, a better study of the track and subgrade is obtained through regular monitoring. Due to the complex of measures for diagnosing the track, a qualitative assessment of the performance of individual operations and the timely detection the railway track faults, as well as subsequent repairs according to the actual state of the track, are carried out.