Our research objective is to contribute to gaining a better understanding of the difficulties inherent to managing interactions between power two-wheeler riders and car drivers. 132 power two-wheeler riders and 94 car drivers have been asked what they perceive as being riskiest in driving situations for the representatives of their generic reference group. From all the answers produced, only those which provide information on risk factors related to the other and the occurrence of interferences due to the dynamic situation have been retained and analysed. The results provide a partial explanation of the difficulties related to the two types of users' taking each other into account. On the one hand, the frequency with which the other is mentioned as a source of risk is linked to the concept of conspicuity. This interpretation is related to the relative frequency of the interactions and the difference of real and perceived vulnerability between the users. On the other hand, the specific risk factors attributed to the other illustrates a mutual misunderstanding or ignorance of the driving situation's determinants. These include various practices among users which can be related to the physical and dynamic characteristics of their vehicle and their level of familiarity with other users. The potential road safety consequences of prior representations of risk factors among users are presented and suggestions for improving road user safety are proposed. Interaction between powered two-wheeler riders and car drivers ; Risk perception ; Threat Prior representations ; Conspicuity
