Vulnerable road users (VRUs) face high collision risks in mixed traffic, yet most existing safety systems prioritize driver or vehicle assistance over direct VRU support. This paper presents ARCAS, a real-time augmented reality (AR) collision avoidance system that provides personalized spatial alerts to VRUs via wearable AR headsets. By fusing roadside 360° 3D LiDAR with SLAM-based headset tracking and an automatic 3D calibration procedure, ARCAS accurately overlays world-locked 3D bounding boxes and directional arrows onto approaching hazards in the user's passthrough view. The system also enables multi-headset coordination through shared world anchoring. Evaluated in real-world pedestrian interactions with e-scooters and vehicles (180 trials), ARCAS nearly doubles pedestrians' time to collision and increases counterparts' reaction margins by up to 4x compared to unaided eye conditions. Results validate the feasibility and effectiveness of LiDAR-driven AR guidance and highlight the potential of wearable AR as a promising next generation safety tool for urban mobility.

翻译：在混合交通中，弱势道路使用者面临较高的碰撞风险，然而现有安全系统大多优先考虑驾驶员或车辆辅助，而非直接支持弱势道路使用者。本文提出ARCAS，一种实时增强现实防撞系统，通过可穿戴AR头显为弱势道路使用者提供个性化的空间警报。该系统融合路侧360° 3D LiDAR、基于SLAM的头显跟踪以及自动3D标定流程，能够准确地将世界锁定的3D边界框和方向箭头叠加到用户穿透式视野中接近的障碍物上。系统还通过共享世界锚点实现多头显协同。在与电动滑板车及车辆的真实行人交互场景中进行的评估（180次试验）表明，相较于无辅助的肉眼观察条件，ARCAS使行人的碰撞时间几乎延长一倍，并将对方反应裕度提升高达4倍。结果验证了LiDAR驱动的AR引导的可行性与有效性，并突显了可穿戴AR作为下一代城市出行安全工具的潜力。