Informing drivers via wearable devices: Impacts of tactile warning locations on takeover performance in automated driving

Drivers' takeover performance is critical to the safety of Level 3 automated driving, making the design of takeover requests (TORs) a central topic in recent ergonomic research. This study proposed a novel approach to delivering tactile TORs through wearable devices. A driving simulator experiment involving 36 participants was conducted to examine how the location of tactile warnings-ear, wrist, abdomen, and tibia-affects takeover performance and user acceptance under various non-driving-related task (NDRT) conditions. Results showed that ear-based warnings elicited the shortest reaction times, while tibia-based cues triggered the strongest braking responses. Wrist-based warnings, despite slightly slower reactions, received the highest acceptance ratings from participants. These findings emphasise the importance of signal placement and reveal a trade-off between objective performance and user preference. We recommend ear-based cues for urgent scenarios and wrist-based cues for routine takeovers. This work offers valuable guidance for designing user-centered haptic interfaces in automated vehicles.