Successive Categorization of Perceived Urgency in Dynamic Driving Situations

The timing of warnings in Advanced Driver Assistance Systems is crucial for a fast and correct reaction, as well as the driver’s acceptance. Knowledge about the human urgency perception is needed to match this timing. We developed a new technique to measure the perceived urgency in dynamic situations and evaluated it in a test track study.

Eight participants drove an equipped test car with constant speeds (30–130 kph) on a test track approaching a preceding vehicle that was either standing or moving with a lower constant speed. Similar to the last second braking method [1], the participants were required not to brake until a collision seemed inevitable. Approaching the vehicle, the participants judged the increasing perceived urgency with successive presses on a steering wheel mounted button to indicate a change of urgency category (3 ascending urgency categories).

We manipulated the speed of the participant’s car and the speed difference. When the participants chose a certain urgency category the relative velocity had systematic effects on the distance and Time-To-Collision (TTC). Higher relative speeds lead to earlier urgency judgements compared by TTC. In addition, the variance of distance and TTC per category between the drivers decreased as the urgency category increased.