Effects of Quantity and Size of Buttons of In-Vehicle Touch Screen on Drivers’ Eye Glance Behavior

ABSTRACT

This article investigates the effects of the quantity and size of touch screen buttons and the task-interleaving strategies on drives’ eye glance behavior. An experiment was conducted on a fixed-base driving simulator with 20 participants. The participants were asked to perform a button search-and-press task on an in-vehicle touch screen while driving. A full-factorial within-subject design was used with three button quantities (4, 8, and 15) and three button sizes (14 mm, 24 mm, and 33 mm). Although a normal distribution was often assumed for the eye glance data in previous studies, our results show that the total eyes-off-road time (TEORT) and glance durations are generally not normally distributed (positively skewed) even after a log transformation. The results show that the number of buttons has an increasing effect on task completion time, TEORT, and long (2+ s) glances. However, in general, no such differences were found for button sizes. Further analysis shows that long glances were strongly associated with drivers completing the task with a single glance. It seems to suggest that a major cause of long glances is that drivers are reluctant to switch the task back to driving at subtask boundaries that are probably associated with the high cost of interruption. These findings confirm the importance of task resumability for in-vehicle user interfaces and have implications that careful task analysis needs to be conducted in the context of multitasking. Certain subtask combinations, such as a visual search followed by pressing the search target, may discourage task interleaving and ultimately compromise driving safety.

KEYWORDS:

• Driving
• visual search
• visual display
• touch screen
• multitasking
• infotainment system

Acknowledgment

This work was financially supported by the Ford-University of Michigan Alliance Project. The authors would like to thank James Rankin and Basavaraj Tonshal at Ford Motor Company for their technical support. The authors would also like to thank the anonymous reviewers for their valuable comments and suggestions.

Additional information

Notes on contributors

Fred Feng

Fred Feng, PhD, is a research fellow at the University of Michigan Transportation Research Institute. His research interests include human–machine interactions, user interface designs, and human performance modeling with applications of road traffic safety, driver behaviors, and the safety of vulnerable road users.

Yili Liu

Yili Liu, PhD, is Arthur F. Thurnau Professor of Industrial and Operations Engineering at the University of Michigan at Ann Arbor. His areas of research and teaching include computational cognitive modeling, cognitive engineering and human factors, and aesthetic and cultural ergonomics.

Yifan Chen

Yifan Chen, PhD, is the manager of Mobility Research at Ford Motor Company. He leads a team to develop innovative technologies for further mobility needs. Previously, he had worked in mobile computing, HMI simulation, and CAD/CAE. Dr. Chen received his PhD in Naval Architecture and Marine Engineering from the University of Michigan, Ann Arbor, in 1993.