Accidents between pedestrians, bicyclists and motorized vehicles: Accident risk and injury severity

Sammanfattning: Popular Abstract in English This work is focused on two accident types: accidents between motorized vehicles and pedestrians, and accidents between motorized vehicles and bicyclists. It aims at better understanding how the number of accidents is related to the number of road users; and how the speed at the site and age of the victim is related to how severe the injuries are. The work relies on several different statistical techniques to study those relations. The results show that there is a relation between the number of road users and the numbers of accidents, that is, if there are more road users, there are more accidents. The results further suggest that the risk of an accident per road user is lower at sites where the number of road user is high, compared to sites where the number of road users is low. This effect is also apparent for pedestrian fall accidents (single accidents) which allow us to reflect over the current theories regarding to why the models show this effect. Risk values and risk curves are frequently used when working with traffic safety, where the probability of serious or fatal injuries is presented against some other variable, for example speed. The thesis suggest an alternative way to interpret those risk values and risk curves, where the approach depends on if it is from the perspective of the individual or from the perspective of the society as a whole. The results furthermore show that the speed environment and the age of the victim are closely related to the probability of sustaining serious or fatal injuries. A considerable proportion of the serious injuries occur in low speed environments, seniors suffer more serious injuries than younger pedestrians and cyclists do, and the effects differ substantially for struck pedestrians versus struck bicyclists.