Situation awareness and workload in driving while using adaptive cruise control and a cell phone

Little work has empirically examined the cognitive construct of situation awareness (SA) in driving tasks involving the use of advanced in-vehicle automated technologies and personal communication devices. This research investigated the effects of an adaptive cruise control (ACC) system, and cell phone use in driving, on a direct and objective measure of SA, and assessed the competition of multiple driving and communication tasks for limited mental resources in terms of driving performance. Eighteen participants drove a virtual car in a driving simulation and performed a following task involving changes in speed and lateral position. Half of the participants were required to respond to cell phone calls and all completed trials with and without use of the ACC system. Task performance was measured in terms of lane deviations and speed control in tracking a lead vehicle, as well as headway distance in the following task. SA was measured using a simulation freeze technique and SA queries on the driving situation. Subjective workload was measured using a uni-dimensional mental workload rating. Results indicated use of the ACC system to improve driving task SA under typical driving conditions, and to reduce driver mental workload. However, the cell phone conversation caused deleterious effects on driving SA and increased driver mental load. The cell phone conversation (secondary task) competed for limited mental resources of drivers, leading to less attention to, and accurate knowledge of, the driving situation. Results also revealed the ACC system to improve driving performance along multiple dimensions; however, the cell phone did not have an effect. The latter result may be attributed to a short duration of the cell phone conversations during the experiment. This study has implications for the implementation of in-vehicle automation to support driver SA under normal driving conditions and regulations on the use of cell phones while driving. Relevance to Industry: The results of this study have relevance to the introduction of advanced automation in commercial vehicles for supporting driver SA and regulation of cell phone use in driving. The study brings to light the critical role of attention-demanding distracter tasks, such as cell phone conversation while driving and using in-vehicle automation. r 2005 Elsevier B.V. All rights reserved.