Licentiatavhandling Göteborg : Chalmers University of Technology. Department of Mechanics and Maritime Sciences, 2017

Introduction: Adaptive cruise control (ACC) is a system that automates the longitudinal control of the vehicle, and maintains safety margins to a lead vehicle. ACC has been shown to have positive safety effects in reducing the exposure to critical situations. However, ACC in normal driving has also been shown to generally decrease the drivers’ attention devoted to monitor the road ahead. A number of studies claim that automated systems, such as ACC, may have detrimental effects, e.g., due to lack of supervisory control. In fact, ACC requires the drivers’ constant supervision to regain control if needed, otherwise drivers may fail to cope with situations beyond the system’s capabilities. ACC is a low level of automation; as these systems evolve unintended effects on drivers’ behavior[A1] may accentuate. Objectives: Automation is an increasingly important area[A2] of research in transportation. There is a need to understand the effects of automation on drivers’ behavior, and to assess the safety implications thereof. Most research is limited to simulator experiments; the effects in real-world driving remain unclear. Methods: Visual behavior was investigated when driving with ACC and a critical situation was encountered in real-world driving. Critical situations were identified as the onset of the frontal collision warning (FCW), a system that warns on an impending lead-vehicle conflict. Results: The findings show that automation does affect visual behavior. In general, compared to manual driving, drivers devoted less attention at the forward road when using ACC. However, the results show that visual behavior is tightly coupled to driving situation characteristics, and drivers are responsive to perceptual cues that alert of an impending threat.