Driver interaction with vulnerable road users: Understanding and modelling driver behaviour for the design and evaluation of intelligent safety systems

Licentiatavhandling, 2017

Every year, more than 5000 pedestrians and 2000 cyclists die on European roads. These vulnerable road users (VRU) are at especially high risk when interacting with motorised vehicles. Safety systems designed to mitigate or avoid crashes with VRU started to enter the market a few years ago and still need to be improved to be effective in all scenarios. Understanding how drivers interact with VRU is crucial to improve the development and the evaluation of safety systems. Today, however, there is a lack of knowledge about driver behaviour in interactions with VRU, which keeps active safety measures from expressing their full potential. This thesis has multiple objectives: 1) to provide new knowledge about driver behaviour in crossing interactions with VRU, 2) to present this knowledge to assessment programs such as Euro NCAP with the goal of improving their system-evaluation scenarios, and 3) to include this knowledge in a counterfactual analysis framework for safety-benefit evaluation. Results showed that the moment in which a VRU becomes visible to the driver had the largest influence on the driver braking response process in driver-VRU interactions. This thesis contributes to experimental methodologies by comparing the steps of the response process in test-track and in driving-simulator studies. Additionally, the thesis describes a driver braking response model and uses the information gained from it to suggest improvements in the design and evaluation of safety systems. Finally, a framework for counterfactual simulations was developed which is suitable for evaluating safety benefits and refining intelligent safety systems (such as autonomous emergency braking and frontal collision warning). This thesis addressed some of the research gaps in the understanding of driver behaviour that have hindered the improvement of driver models and their application to the design and evaluation of safety systems.