Supplementary data for the paper 'Head-locked, world-locked, or conformal diminished-reality? An examination of different AR solutions for pedestrian safety in occluded scenarios.'

Many collisions between pedestrians and cars are caused by poor visibility, such as occlusion by a parked vehicle. Augmented reality (AR) could help to prevent this problem, but it is unknown to what extent the augmented information needs to be embedded into the world. In this virtual reality experiment with a head-mounted display (HMD), 28 participants were exposed to AR designs, in a scenario where a vehicle approached from behind a parked vehicle. The experimental conditions included a head-locked live video feed of the occluded region, meaning it was fixed in a specific location within the view of the HMD (VideoHead), a world-locked video feed displayed across the street (VideoStreet), and two conformal diminished reality designs: a see-through display on the occluding vehicle (VideoSeeThrough) and a solution where the occluding vehicle has been made semi-transparent (TransparentVehicle). A Baseline condition without augmented information served as a reference. Additionally, the VideoHead and VideoStreet conditions were each tested with and without the addition of a guiding arrow indicating the location of the approaching vehicle. Participants performed 42 trials, 6 per condition, during which they had to hold a key when they felt safe to cross. The keypress percentages and responses from additional questionnaires showed that the diminished-reality TransparentVehicle and VideoSeeThrough designs came out most favourably, while the VideoHead solution caused some discomfort and dissatisfaction. An analysis of head yaw angle showed that VideoHead and VideoStreet caused divided attention between the screen and the approaching vehicle. The use of guiding arrows did not contribute demonstrable added value. AR designs with a high level of local embeddedness are beneficial for addressing occlusion problems when crossing. However, the head-locked solutions should not be immediately dismissed because, according to the literature, such solutions can serve tasks where a salient warning or instruction is beneficial.

行人与机动车的碰撞事故多因视线不良引发，例如被停放车辆遮挡视线。增强现实（Augmented Reality，AR）可用于规避此类问题，但目前尚未明确需将增强信息以何种程度嵌入真实场景。本研究借助头戴式显示器（Head-Mounted Display, HMD）开展虚拟现实实验，招募28名被试，在“车辆从停放车辆后方驶来”的场景中测试多款AR设计方案。实验条件涵盖：遮挡区域的头部锁定实时视频流（即该视频流固定于头戴式显示器视野内的特定位置，记为VideoHead）、跨街道展示的场景锁定实时视频流（记为VideoStreet），以及两种共形缩减现实（Diminished Reality）设计：安装于遮挡车辆上的透明显示装置（记为VideoSeeThrough），以及将遮挡车辆设置为半透明的方案（记为TransparentVehicle）。设置无增强信息的基线条件作为对照组。此外，分别在添加与未添加指示来车位置的引导箭头的条件下，对VideoHead与VideoStreet两种方案进行测试。每名被试完成42组测试，每种实验条件下各6组；测试过程中，被试认为可安全横穿道路时需按下按键。按键响应占比与附加问卷的反馈结果显示，缩减现实类的TransparentVehicle与VideoSeeThrough方案获得了最高认可度，而VideoHead方案则引发了一定程度的不适与不满情绪。对头偏航角的分析结果表明，VideoHead与VideoStreet方案会导致被试在显示器屏幕与来车之间分散注意力。引导箭头的使用未体现出显著的附加价值。局部嵌入程度较高的AR设计，有助于解决横穿道路时的视线遮挡问题。但不应直接否定头部锁定类方案，现有研究表明，此类方案可适用于需要突出警示或指令的任务场景。