SUBJECTIVE ROAD CATEGORIZATION AND SPEED CHOICE

In this study, two experiments were performed. The aim of the first experiment was to investigate: (1) how road users categorize roads outside built-up areas; and (2) how well this categorization maps onto the 'official' categorization. Subjects sorted freely 32 pictures of existing roads outside built-up areas (belonging to one of four 'official' categories in the Netherlands). Multidimensional scaling analysis and cluster analysis show that the 'official' 'freeway' category is also a subjective category. For the other 'official' categories (motorway, road closed for slow traffic, and road for all traffic), the subjective categorization does not correspond to the 'official' categorization. In the second experiment, the first experiment pictures, supplemented with manipulated versions of these pictures in which road elements were systematically added, deleted or changed, were presented on a computer screen. The subjects typed in the speed they would drive on these roads. The results indicate that side markings and the road width are important speed-influencing elements. There is a relationship between the subjective categorization resulting from the first experiment and the driving speed choice from the second experiment. This shows that the speed one drives is strongly connected to how drivers categorize roads.