Where's My Cellphone: Non-contact based Hand-Gestures and Ultrasound haptic feedback for Secondary Task Interaction while Driving

Drivers regularly use their smartphones to perform secondary tasks while driving, which can negatively impact traffic safety. In such complex interaction, multimodal feedback has been associated with lowering driver distraction. We investigated four methods for completing a phone-based secondary task while driving: smartphone in hand, smartphone in a rack, buttons on the steering wheel with Head-up-display (HUD), and mid-air gestures with an ultrasound haptic feedback and a HUD. Participants (N=16) drove the Lane Change Test (LCT) simulator with each method to complete predefined secondary tasks. To measure performance in primary task, we recorded lane deviations and for secondary task we measured response times and errors. Additionally, the participants filled in the NASA-TLX questionnaire and ranked each method according to their preferences. The results showed that the performance and preference for the hand and rack conditions were similar, while performance with buttons and gestures was worse, even with ultrasound haptic feedback, than in hand and rack conditions. The results highlight the importance of rigorous user testing when introducing new modalities for in-vehicle interaction to enhance primary and secondary task performance.