Three factors are involved in car accidents :​ the road, the vehicle and the driver. Of these, the first two have recently received considerable attention;​ the third factor, the driver behind the wheel, is probably the most important. Attention have been paid to the last two factors. The present study characterizes low vigilance periods relative to driver's drowsiness by simultaneous analysis of the recorded EEG, steering wheel movements and vehlcle speed signals during six hours driving period. The mechanical parameters thresholds of the vehicle have been discussed.

This paper examines firstly the state of the art in monitoring driver states. It reviews and discusses empirical studies that assessed the relationship between EEG indices and measurements of car mechanical parameters which are used as a criteria of vigilance impairment. We have secondly compared EEG indexes with the absolute fluctuations of the mechanical settings and we have evaluated thresholds of the steering wheel movements relative to physiological impairments. We have examined their variation during the trip versus theta and alpha rhythms. Their changes are used to define thresholds and to quantify driver impairments in real traffic. We have defined two and seven degrees thresholds for the steering wheel movement fluctuations. For the vehicle speed fluctuations, the results show that it's impossible to obtain some significant threshold value. We also noted that some periods where ΔΦ ≥ 2° and theta energy is not predominate, alpha bursts last 1.5 seconds or more. We have also found that amplitude of the alpha waves only is unable to define the steering wheel movements low thresholds. Sometimes, "delay effects" between EEG and vehicle variables have occured.