Ensuring the transport process requires proper interaction of all parts of the system "driver - car - road - environment" and its subsystems. In this case, the driver is often a "weak" component of the system, and his actions can reduce the level of road users` safety. It should be noted that the reliability of the driver can be considered as the probability of his trouble-free and error-free operation, as well as the proper level of his regulatory mechanisms functioning. In this case, to analyze the activities and readiness of the driver for his professional activities, indicators of functional status are often used. Thus, the study of the "human factor" in the transport process is an important task to ensure the reliability of the whole transport system. Today the most of all transportation is carried out by road. The timeliness and safety of cargo delivery and passenger safety depend on the driver's actions. At the same time, the driver is influenced by a considerable number of external environmental factors during his work. One of the most important factors is the mountainous traffic conditions, which often have many changes in plan and the profile of roads. Another feature of such traffic conditions is the height above sea level, affecting the human body, particularly its functional state. Considering the above, the paper measures the heart rate variability of bus drivers moving on a route that was partly in the mountain's conditions. During the research, video recording and registration of the vehicle's geolocation were also carried out. This made it possible to establish indicators of the driver`s functional state in specific periods. After processing the obtained values, the influence of mountainous traffic conditions on the bus drivers` indicator of regulatory systems’ activity was established.