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.

行人与机动车之间的碰撞多由视野受限引发，例如被停放车辆遮挡视线的情况。增强现实（Augmented Reality）可助力规避该类问题，但目前尚不明确需将增强信息在真实场景中嵌入至何种程度。本研究借助头戴式显示器（Head-Mounted Display，HMD）开展虚拟现实实验，共招募28名受试者，使其体验多款增强现实设计方案，实验场景设定为：一辆机动车从停放车辆后方驶出并接近受试者。实验设置包括：头部锁定式遮挡区域实时视频流（即该视频在头戴式显示器视野中固定于特定位置，记为VideoHead）、世界坐标系锁定式街对面视频流（记为VideoStreet），以及两种共形减现实（Diminished Reality）设计：在遮挡车辆上设置透明显示屏的方案（VideoSeeThrough），以及将遮挡车辆设为半透明的方案（TransparentVehicle）。设置无增强信息的基线条件作为对照基准。此外，针对VideoHead与VideoStreet两种条件，分别测试了添加与未添加指示来车位置的引导箭头的情况。每名受试者需完成42组测试，每种实验条件对应6组测试；测试过程中，受试者认为自身可安全横穿道路时需按下按键。按键响应占比与后续附加问卷的反馈结果显示：减现实类的TransparentVehicle与VideoSeeThrough方案获得了最高的认可度；而VideoHead方案则引发了部分受试者的不适与不满。对头部偏航角的分析结果表明：VideoHead与VideoStreet方案会导致受试者在显示屏与来车之间分散注意力。引导箭头的添加并未带来可观测的附加价值。具备高局部嵌入度的增强现实设计方案，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式方案，因为已有研究表明，此类方案适用于需要突出警示或指令的任务场景。