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Drivers are still required to perform the takeover task in highly automated vehicles. This task, which is cognitively and physically demanding, may present challenges for older adults due to general age-related declines in perception and cognition. Tactile modalities that may not be occupied by many non-driving-related tasks could serve as a potential solution for delivering takeover requests. Among these, directional vibrotactile stimuli presented via a wrist-worn device represent a promising approach. However, the effects of the two common types of directional vibrotactile patterns, dynamic patterns that vibrate sequentially at different locations and static patterns that vibrate at fixed locations, are still unknown. Therefore, this study aimed to investigate the effect of age (younger and older adults), vibrotactile pattern types (Baseline, Full-Dynamic, Semi-Dynamic, and Static), and interpulse interval (shorter (300 ms) and longer (800 ms)) on takeover performance. Forty participants (20 younger and 20 older adults) were engaged in the SAE Level 3 driving simulator study. Overall, Static and Baseline patterns were associated with faster reaction and takeover times and were perceived as more useful and satisfactory compared to the Full-Dynamic and Semi-Dynamic patterns. Shorter interpulse intervals (300 ms) for vibrotactile takeover requests resulted in better takeover performance, as indicated by shorter reaction and takeover times compared to longer interpulse intervals (800 ms). Finally, younger adults reacted faster to vibrotactile takeover requests than older adults did. The findings from the current study may inform the design of human–machine interfaces on wearable devices for next-generation automated vehicles. 

The imperfections in the driving automation system have challenged older adults because the takeover process is cognitively and physically demanding. Due to the wrist being more vibration-sensitive, the haptic display on the smartwatch could be a good option to warn the driver. However, the preference between two vibrotactile patterns, dynamic patterns (vibrating sequences at different locations on the smartwatch) and static patterns (vibrating at certain locations on the smartwatch), is still unclear. Therefore, this study examined the effects of vibrotactile patterns between younger (mean age = 30.97) and older adults (mean age = 69.45) using a national survey. Three hundred forty respondents’ data were collected. The results showed that static patterns received higher usefulness and satisfaction scores than dynamic patterns. However, no age differences were found. These findings provide a potential guide for the next-generation takeover warning system on wrist-wearable devices in the automated system. 

With SAE Level 3 automated vehicles handling most driving tasks, there are still situations when the driver needs to take over. Multimodal displays have been introduced to inform drivers of the need to take over for critical scenarios (e.g., in construction zones) in instructional or informative formats. However, the effects of multimodal displays on takeover performance for drivers with hearing impairments are still unclear. Therefore, the goal of this study was to investigate how signal type (single tactile (T), single visual (V), and visual and tactile combined (VT)), information type (instructional, informative, and baseline), and hearing impairment (hearing-impaired and non-hearing-impaired drivers) affect drivers’ takeover performance. Findings show that signal type significantly influenced reaction and takeover times, with multimodal signals (VT) resulting in faster reactions compared to single modal signals. Additionally, the baseline condition yielded the faster reaction times compared to both instructional and informative formats. Hearing impairment, however, did not significantly affect reaction and takeover times. Findings may inform the development of future vehicle interfaces to assist drivers with hearing impairments. 

Higher levels of driving automation make effective takeover requests critical. The wrist’s sensitivity to vibration makes wristband devices a potential carrier for sending these requests. However, the impacts of conveying takeover requests through directional vibrotactile patterns such as dynamic patterns (sequential stimuli occurring at different locations on the wrist) and static patterns (fixed stimuli at the same locations on the wrist) are unclear. Therefore, this study examined the effects of directional vibrotactile patterns on takeover performance among younger and older adults. Participants responded to four patterns (two dynamic, one static, and one baseline) in a simulated SAE Level 3 automated vehicle. Takeover performance was evaluated using reaction time and takeover time. The results show that the static and baseline patterns had shorter reaction and takeover times compared to the dynamic patterns. In addition, younger adults react faster to takeover requests compared to older adults. Findings provide important insights for the future design of human-machine interfaces via wristband devices for automated vehicles. 

Automated vehicles may enhance the quality of life by empowering individuals and promoting independent mobility, especially for older adults. However, takeovers are still required occasionally. To ensure a safe transition during the takeover, meaningful tactile displays as takeover requests could be a good option to improve takeover efficiency. Previous studies have examined the effects of tactile takeover request more from an objective perspective, however, subjective evaluations that could reach larger and more diverse sample sizes have not been extensively conducted yet. Therefore, the goal of this study was to investigate drivers of different age groups (younger and older adults) on their preference of vibrotactile displays, varied in information formats (instructional and informative) and locations (seat back and seat pan), on a large population scale ( n = 353) through a national survey. The results indicated a preference for informative patterns over instructional patterns and displays on the seat back over the seat pan. Also, a higher level of perceived urgency was noted in older participants (age ≥ 65) compared with younger participants. These findings may inform the design of next-generation tactile interfaces in automated systems.