Estimating the severity of safety related behaviour.

The aim of this work is to be a starting point for a more thorough description and analysis of safety related road user behaviour in order to better understand the different parts forming the traffic safety processes. The background is that it is problematic to use analysis of crash data and conflict data in the everyday traffic safety work due to low occurrence rates and the focus on rather exceptional and unsuccessful events. A new framework must consider the following aspects: (1) The importance of feedback to the road users. (2) Inclusion of more frequent events, "normal" road user behaviours and the possibility to link them to a severity dimension. (3) Prediction of safety/unsafety based on the more frequent events. By constructing severity hierarchies based on a uniform severity dimension (Time to Accident/Conflicting Speed value) it is possible to both describe the closeness to a crash and to get a comprehensive understanding of the connection between behaviour and safety by both considering unsuccessful and successful interactive situations. These severity hierarchies would make it possible to consider road users' expectations due to feedback and estimate its safety relevance.