The object of this study is the process of driver’s labor activity on road sections in the city's transport system in the process of transporting goods and passengers. The influence of traffic congestion on the level of the functional state of a choleric driver and a phlegmatic driver, which are opposite types of temperament, is considered. The hypothesis of the study is that the level of driver fatigue, determined by a change in his functional state in a traffic jam, affects the driver's reaction time and road safety and depends on the driver's condition and the parameters of the traffic jam. The degree of fatigue, which is determined by a change in the functional state of the driver, is determined based on the concept of the cardiovascular system as an indicator of the adaptive activity of the driver's body by measuring the electrocardiogram. To assess the level of driver fatigue, the irregularities of the electrocardiogram cardio intervals are analyzed, which are a universal response to any type of load: physical or mental. The level of fatigue is assessed in arbitrary units using a special algorithm that takes into account statistical indicators, histogram indicators and data from the spectral analysis of cardio intervals. Regularities of changes in the level of fatigue of a choleric driver and a phlegmatic driver, depending on various conditions of stay in a traffic jam, were obtained using nonlinear models of changes in their functional states. It was revealed that the most significant factor influencing the final level of fatigue of a choleric driver in a congestion is the duration of traffic congestion, the effect of which on the output function is manifested only in conjunction with the initial level of fatigue. The next most important parameter influencing the change in the level of fatigue is the initial value of the level of fatigue before the mash. The influence of the age of the choleric driver on the level of his fatigue in the congestion was less pronounced. As a result of the studies carried out and the revealed patterns, it was found that the duration of the congestion does not significantly affect the condition of the phlegmatic driver. The most important factor influencing his condition is the initial level of fatigue before entering the congestion. It was also found that the conditions of being in a traffic jam most significantly affect older choleric drivers (fifty or more years old) compared to young drivers thirty years old. Analysis of the research results showed that congestion lasting more than ten minutes leads to a significant increase in the level of fatigue of a choleric driver. Such situations can lead to an increased probability of a road traffic accident by a choleric driver. The obtained patterns of changes in the functional state of a choleric driver and a phlegmatic driver in a traffic jam allow predicting the driver's behavior after a traffic jam and assessing various options for the development of the road traffic situation that affect road safety.