The environment within a motor vehicle is believed to affect the driving performance and wakefulness of the driver. Knowledge, about how and to what extent the driver is affected, is however lacking due to the fact that very few realistic studies have been carried out. The effects on traffic safety, if any, are therefore also unknown. The objective of the present study was to assess the influence of noise, infrasound and temperature on performance and wakefulness of drivers performing realistic driving tasks in a simulator, where they were exposed to realistic and controlled environmental as well as driving conditions. Forty-eight young, healthy individuals "drove" the VTI driving simulator for about four simulator for about four hours. They were exposed to different combinations of noise, infrasound and temperature. Two levels of each of these variables, representing low and high levels measured in real traffic, were used. The experimental design thus included eight different experimental conditions (combinations) with six drivers exposed to each condition. As dependent measures of driving performance we used steering precision, speed holding and stimuli-induced reaction time, while EEG, ECG and EOG were recorded for the assessment of wakefulness. Audiometry was carried out, before and after exposure, to observe possible temporary hearing threshold shifts. The answers from questionnaires given to the subjects indicate their subjective evaluations of sleepiness and impaired performance. The general interpretation of the test results is that the acoustic and thermal environments which "normally" exist in road vehicles of today influence performance and wakefulness in different ways. It is not evident that e.g. the lowest noise level forms the best environment from performance point of view.
Abstract