Attention of drivers is a key factor of road safety. Inattentive drivers are dangerous to their surroundings and cause a considerable number of accidents. However, decline of attention, especially during long rides, is natural and it is worth to know if it can be investigated from electric activity of the brain. Since there is an evidence of relationship between attention and P3 component which is widely used in design and analysis of experiments by the method of event related potentials (ERPs), the ERP experiment based on auditory stimulation was designed and performed on tested subjects, which drove a car simulator on a monotonous track. The background of the used method, experimental design, data processing, and results of the performed experiments are described in this paper.