The effect of autonomous speed control system: An investigation on minimum headway and driver's acceptance

This study focuses on minimum headway and driver acceptance associated with an Autonomous Speed Control System (ASCS) in autonomous vehicles. For this study, three driving environments have been considered, including: residential, rural, and highway. The results showed that headway has a significant effect on the participant's opinion of the ASCS (i.e., workload, confidence, comfort, safety and acceptance), whereas no significant effect of the driver's gender or traffic speed was observed on the driver's opinion. At different driving speeds, the headway assigned by the participants remains stable with an average of 1.12-1.26s. This study demonstrates that most drivers maintain spacing between vehicles relying on their judgment on distance, and their judgment on headway is unreliable (i.e., most drivers are unable to jointly consider both speed and distance). These insights will help to inform the design of future autonomous vehicle applications, and will serve as an input for calculating the route capacity of intelligent transportation systems.