G4-1 A Study of Multi-touch Screen Installation in Vehicles for Single-touch and Gestural Operations

Abstract

Touchscreens have been used for human-machine interactions in vehicle for years; researchers paid more attention to using touchscreen displays when driving was the primary task and the driving performance was the main concern. However, it is not legal to operate touchscreen devices while driving in most of modern countries. On the other hand, a driver may occasionally control in-vehicle systems through touch or even gestural operations on the touch display. The situation is becoming more and more popular and worthwhile further study. The current study investigated three different installations of a multi-touch screen in vehicle at high (around the driver's eye height in sitting), middle (around the height of the driver's shoulder) and low (around the height of the driver's waist) positions. Twenty-seven voluntary participants (aged 23.93±0.68 years old) were recruited to perform single-touch and gestural operations in a simulated car cabin. Their performance in accuracy for the two experimental tasks and subjective responses regarding difficulty, fatigue and preferences of the task and interfaces were recorded. The results of the study showed that, regardless of the single-touch target clicking task or the multitouch target fitting task, the averaged errors over all target positions were the least for the middle installation and were the highest for the low installation. When user performance for different target sizes was compared in the gestural operations, participants tended to deviate more when the target size was small (100-pixel diameter) but manipulated the size more accurately when it was big (200-pixel diameter). The subjective evaluation through questionnaires showed that participants preferred the middle installation. The high installation was considered more difficult and caused greater fatigue on right neck, shoulder, upper extremities, wrist, and thumb belly areas. Based on the results of the current study, the middle installation is recommended for its higher accuracy and less fatigue. The upper installation, despite being recommended by other literature, caused greater errors, higher difficulty and fatigue, resulting the least preference. The difficulty and fatigue was not revealed for the lower installation, but it caused lower accuracy in gestural operations. This study could contribute to future design of in-vehicle touch interfaces in that the accuracy of single-touch and multi-touch tasks may be improved by installing the touchscreen at a middle height (around shoulder level). Future studies may consider verifying experiments in an interface simulating real in-vehicle information systems and increasing the number of data collected so that the result can be more applicable in reality.