The aim of the present paper is to identify the effect of situation complexity and driving experience on performance through subjective and objective levels of tension. The main contribution of this paper to the Cognitive Ergonomics field consists in the identification of accidents’ factors of young drivers faced to a stressful event. Thirty-two drivers (16 novices vs. 16 more experienced) were randomly assigned to three levels of situation complexity (simple, moderately complex and very complex) in a driving simulator. Physiological and subjective levels of tension were respectively associated to “pedestrian crossings” events and to the whole situations. Driving performance corresponded to reaction times and to collisions’ number with the pedestrians. Results showed that novice drivers had weaker performance than the more experienced once, even though their high level of objective and subjective tension due to situation complexity improved their performance. Therefore, target driving assistance systems to deal with hazard events could reduce road accidents among young novice drivers.