Driving skill was investigated using a measure of automatization of skill based on the amount of concurrent use of car controls. The measure identified four groups of drivers with a uniform increase of concurrent control use, and two groups with different patterns of automatization. The validity of the automatization measure and the effects of the traffic environment was investigated in a study were the subjects drove one of three routes, with similar characteristics. The automatization measure differentiated systematically the use of controls in the different groups. The environment also influenced car control independent of the automatization measure. The automatization measure also systematically differentiated driver traffic experience and accident information. The reliability of the automatization measure was investigated in a single-subject study were the subject drove the same route, in both directions, during a period of three months. There were no measurable changes in the driving skill measure during the period studied. The effects of a secondary task on the automatization measure and on car control use were investigated in a study with subjects driving the same route with and without a mobile telephone task. The task did not influence car control concurrency, but did lead to a general decrease in control use. The effects of stabile changes in the environment on the automatization measure were investigated in a study were drivers drove the same route in summer and in winter conditions. The results showed a decrease in car control concurrency and car control use in the winter condition as compared to the summer condition. The relationship between personality factors, verbal reasoning tasks about traffic situations and the automatization measure was investigated in study were the drivers drove a standard route, filled out a questionnaire containing 5 personality scales, and reasoned about the consequences and influences of three different traffic situations in an interview. The ego-strength scale showed a significant lower level in one of the deviant automatization measure groups, but no other scale or reasoning task displayed any relationship with the automatization measure. The results are discussed from the point of view of a presented driving skill model.
Samenvatting