How often are road users (too) tired?

Almost everyone is tired sometimes, due to a short or poor night’s sleep for instance. A questionnaire study among Dutch drivers [9] showed that, in the previous year, 55% of the drivers had sometimes driven while being tired. For that same period, a quarter of them admitted having driven while being so tired that they had trouble keeping their eyes open and 4% admitted having actually fallen asleep behind the wheel. Compared to car drivers, truck drivers more often appear to be very tired while driving or to (almost) fall asleep [3].

These data are generally based on questionnaires and therefore on self-reported data. Objective and large-scale measuring of fatigue while driving is very hard.