## 4 Intelligent Wearable Solutions for VRU Safety: Trends, Challenges, and Opportunities
### Wearable Assistive Devices for Visually Impaired Users
conducted a comprehensive comparison of 12 different wearable technology solutions [70], indicating that no single system could fully meet all needs, and future development should focus on complementing rather than replacing the traditional white cane. Although these early systems pioneered the exploration of various feedback modes, they were limited by the processing capabilities and sensor technologies of the time, facing challenges such as large device size and short battery life in practical applications. These limitations prompted researchers to seek more lightweight solutions focused on specific needs, such as chest/neck-mounted systems for upper body protection. Compared to computer-assisted systems, neck and chest-mounted devices offered an innovative approach, particularly addressing the issue of upper body obstacles that traditional white cane struggle to detect. [PERSON] et al. developed a head collision warning system using chest-mounted miniature ultrasonic sensors [68], capable of precisely detecting obstacles within a 1.5-m range, providing visually impaired individuals with sufficient reaction time. Based on a similar concept, [PERSON] et al. designed a necklace-like ultrasonic system [69] that provided environmental awareness assistance through tactile feedback, effectively reducing upper body collisions during walking and significantly improving the safety of independent travel for visually impaired individuals. With advances in computer vision technology, the chest-mounted camera systems by [PERSON] et al. [71] and [PERSON] et al. [75] not only detected obstacles but also identified traffic signals and pedestrian crossings, guiding users to safely cross intersections through voice instructions. Furthermore, the chest-mounted binocular camera system [5] of [PERSON] et al. further improved the accuracy and intelligence of obstacle detection, automatically prioritizing obstacles based on distance and movement status and providing users with more precise warning information. These designs focus on addressing the blind spots of white cane while not interfering with users' ability to operate the white cane, showing a technological evolution from simple ultrasonic sensing to the integration of computer vision and intelligent processing. While these systems effectively addressed upper body protection issues, they still primarily relied on voice prompts for environmental information transmission, which had limitations in noisy environments, prompting researchers to explore alternative perception channels such as tactile feedback. In the development of sensory feedback technologies, tactile feedback has become an essential component of navigation systems for the visually impaired due to its intuitiveness and reliability in noisy environments. [PERSON] et al. developed a belt system integrating mobile phone vibration motors into wearable devices [62], conveying direction and distance information through vibrations of varying positions and intensities, which was simple to use and required almost no special training. Similarly, based on waist-worn concepts, the smart belt of [PERSON] et al. utilized different frequencies from vibration motors on the left and right sides [67] to effectively distinguish between guidance path directions and obstacle positions. In terms of hand-based tactile feedback, the wrist-worn ultrasonic sensor system of [PERSON] et al. [63] enabled users to successfully complete complex navigation tasks after brief training, while the smart glove systems by [PERSON] et al. [65] and [PERSON] et al. [66] transmitted more detailed spatial information by stimulating different fingers, with tests showing users could identify obstacle positions with high accuracy and successfully avoid collisions. The dual wristband system by [PERSON] et al. provided three-directional collision warnings [64], not only significantly reducing the number of collisions but also improving the rate of correct navigation decisions when directional information was available.