This lecture explores the levels of vehicle automation, focusing on human driver involvement and system control. It delves into the impact of control transitions between adaptive cruise control and manual driving on traffic efficiency and safety, using data from on-road experiments. The speaker presents a modelling framework to analyze driver choices during control transitions, considering risk perception and task difficulty evaluation. Additionally, the lecture discusses the influence of automated vehicles on traffic safety and driver distraction, based on naturalistic driving studies. It concludes by examining factors affecting driver deceleration behavior and safety interactions with pedestrians, as well as the impact of automation on traffic violations.