Effects of Design Variables of In-Vehicle Touch Interface on Driving Performance, Glance Behavior, and Subjective Workload

Abstract

Objective: This study investigated the effects of design variables in in-vehicle touch user interfaces in terms of driving performance, glance behavior, and subjective workload. Background: Touch user interfaces are commonly used as in-vehicle information systems (IVISs). However, touchscreen design variables that may affect driver behavior have not been thoroughly investigated. Method: We conducted a driving simulation experiment involving an item searching task and a menu task. Each task included two design variables (item searching task: item numbers per screen and presentation format; hierarchical menu task: menu type and menu orientation consistency). Results: The results showed that the number of items per screen and menu orientation consistency have significant effects on driver behavior, whereas the presentation format and menu type exhibit no significant effects. By analyzing the differences in the drivers' age, we found that the effects of independent variables vary by age. Conclusion: Based on the results of this study, the following conclusions and recommendations are proposed for the design of an in-vehicle touch interface: 1) When designing menus or lists for applying a touch task while driving, it is recommended that the number of items per screen be eight or less to reduce its impact on the driver behavior, 2) When designing a menu, the orientation of each menu level should be unified so that there is no negative influence of disorientation, and 3) When the menu structure has a simple structure, differences in the menu structure (whether expandable or sequential) have a weak effect on the driving behaviors. However, if the complexity of the information structure required by the task increases, it is necessary to be cautious about making an approach based on this conclusion. Application: The findings in this study can provide insight into the design of a touchscreen-based IVIS when considering driving safety.