The driver's reaction time is the most important characteristic when driving. The driver's reaction time is the period of time from the moment the stimulus appears in the driver's field of vision until the start of the action (application of the brake pedal, accelerator, steering wheel). The response time to stimuli depends on: the driver's age; the state of his health; mental state; alcohol or drug consumption; if at the moment he is in the vehicle alone or with a passenger, etc. The functional state of the driver is a complex of characteristics of the functions and qualities of the operator, which directly or indirectly characterizes the performance of labor activity. This definition draws a line between the state of a person and the state of his individual physiological and psychophysiological functions. One of these indicators is the stress index. Heart rate is a stable and accurate indicator of functional status. The experiment involved drivers with 10-16 years of experience. The driver's cardiogram was recorded using a portable Holter and analyzed in the CardioSens CS system. According to the degree of danger, conflict situations are divided into three types: light, medium and critical. The degree of danger of a conflict situation is determined by the appearance of critical accelerations. A racelogic device was used to register the acceleration parameters. The obtained dependences of the change in the functional state of the driver and the reaction time in accordance with the number of conflict situations while driving indicate significant fluctuations in these indicators. Change in reaction time from 0.7 sec. up to 1.5 sec. associated with significant psychophysio-logical stress on the driver, the number of conflict situations of various types: the appearance of a pedestrian, dangerous maneuvering of other vehicles, etc. At the same time, the driver's stress may increase by more than 2.5 times. The article discusses an approach to modeling the driver's reaction time, taking into account the influence of conflict situations on city streets. Experimental studies of the regularities of changes in the reaction time, the stress index of drivers in traffic on city streets have been carried out. Two factor models have been built, taking into account the mutual influence of factors of movement time in urban conditions and the number of conflict situations.