Day versus night driving in real traffic and on a driving simulator during an 800 km all-highway drive

Driving performance was examined during daytime as opposed to night time during a prolonged drive in real traffic and on a simulator. Eight men and one woman, 25-65 years, participated. Subjects drove an 800 km all-highway drive twice - during daytime and night time - with a 24hr-interval. A driving simulator test was scheduled at the start, halfway, and upon arrival. During real driving, the standard deviation in the steering position was significantly higher from noon till 16:00, and from midnight till 3:00/4:00. Average driving speed was higher during the night, except from 1:00/2:00 till 3:00/4:00. Performance on the simulator did not correspond to this pattern. Concluding, circadian factors had a major impact on driving performance in real traffic. Furthermore, the relative validity of the simulator used, could not be established. This seemed to be related to poor motivation during the simulator tests.