Abstract
The research reported in this article considers the effects of automating driver's control tasks. Driving can be broken down into 3 general subtasks: navigation, control, and hazard avoidance. Control can be further subdivided into lateral control (position in lane) and longitudinal control (speed and leading headway). Lateral control can be automated by an active steering (AS) system, and longitudinal control can be automated by an adaptive cruise control (ACC) system. Previous research has used driving simulators to consider the effects of driver workload and the ability to reclaim control with these systems. There are, however, some questions about the validity of driving simulators, and this research sought to validate a driving simulator. This was achieved by comparing responses on a secondary task and driving style questionnaire in both a road car and a driving simulator. When validity was established, a comparison of 4 levels of automation was undertaken: manual, ACC, AS, and ACC plus AS. The results showed no reduction in workload associated with ACC over manual driving, but reduction in workload associated with AS and further reduction in workload associated with ACC plus AS. Despite these reductions in workload, there were no adverse affects on normal driving performance. However, the presence of vehicle automation seemed to make drivers less likely to reclaim control in an emergency-braking scenario.