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The purpose of this study was to identify the influence of situation complexity and driving experience on subjective workload and driving performance, and the less costly and the most effective strategies faced with a hazard pedestrian crossing. Four groups of young drivers (15 traditionally trained novices, 12 early-trained novices, 15 with three years of experience and 15 with a minimum of five years of experience) were randomly assigned to three situations (simple, moderately complex and very complex) including unexpected pedestrian crossings, in a driving simulator. The subjective workload was collected by the NASA-TLX questionnaire after each situation. The main results confirmed that the situation complexity and the lack of experience increased the subjective workload. Moreover, the subjective workload, the avoidance strategies and the reaction times influenced the number of collisions depending on situation complexity and driving experience. These results must be taken into account to target the prevention actions.

The distinction between several components of mental workload is often made in the ergonomics literature. However, measurements used are often established from a global score, notably with several questionnaires that originally reflect several dimensions. The present study tested the effect of driving situation complexity, experience and subjective levels of tension and alertness on each dimension of the NASA-TLX questionnaire of workload, in order to highlight the potential influence of intrinsic, extraneous and germane load factors. The results showed that, in complex situation, mental, temporal and physical demand (load dimensions) increased, and that novice drivers presented high physical demand when subjective tension was low on performance. Moreover, increase of mental and physical demand increased effort. It thus, appears essential to distinguish the different components of mental workload used in the NASA-TLX questionnaire. Practitioner Summary: Currently, global score of NASA-TLX questionnaire is used to measure mental workload. Here, we considered independently each dimension of NASA-TLX, and results showed that mental load factors (driving situation complexity, experience, subjective tension and alertness) had a different effect on dimensions, questioning global score use to evaluate workload.

The aim of the present study is to identify when drivers perceive that they are overloaded by an unexpected event, as a function of the situation complexity and their driving practice. The main contribution of this paper to the Cognitive Ergonomics field is that the experimentation allows identifying several factors which show that drivers’ activity is not always adapted to unexpected situations. Fifty-seven young drivers (15 novices with a traditional driving education, 12 early-trained novices, 15 drivers with three years of experience and 15 drivers with at least five years of experience) were randomly assigned to three levels of situation complexity (simple, moderately complex and very complex) in a driving simulator. Self-reported levels of workload during unexpected pedestrian crossings were collected by a questionnaire (NASA-TLX) between each situation. Driving performance (reaction time to a pedestrian crossing that suddenly appears; number of collisions with this pedestrian) was also analysed. The experiment assessed the effect of four levels of driving experience and three levels of situation complexity on subjective workload and driving performance. Results confirmed that early-trained drivers have a higher subjective workload than more experienced drivers. Nevertheless, whatever the situation and the group, the increase of workload and RT provoke an increase of the number of collisions. Therefore, the driving automation acquired with experience doesn’t allow avoiding accidents when an unexpected event appears. Subjective and physiological data will be compared in a second study in order to identify if drivers’ behavior is more based on their state perception or on their physiological change.