都市中的人行地下道因位於地表下，因此給人的印象大多有黑暗、封閉、不確定性及不安全等。本研究目的即要探討哪些人行地下道空間特質會影響使用者安全知覺，並藉此提出可增加安全感的地下道設計建議。由於人們對地下道的安全認知多焦點於地下「通道」部分，常會忽略「地面結構」與「入口階梯」也會影響使用者對地下道安全感的評估，故本研究將以照片評估法來測量受測者對此兩種空間特質之安全知覺。研究結果：(1)地上結構之頂蓋若能透光、側立面通透面積比越高、結構輕量化及入口寬度越寬，可增加安全知覺；(2)入口階梯與外界聯繫感越高、寬度越寬、可直視底端通道、階梯長度較短、底端照度越高及照明偏暖色光，對安全感具有顯著提升作用。

The urban pedestrian underpass is located under the surface, and therefore gives mostly the impression of darkness, isolation, uncertainty, and insecurity etc. This study aim is to examine which spatial characteristic of underpass can influence user safety perception, and to give recommendation improving underpass design and enhancing the sense of security. Due to the fact that people focalize on the safety of underpass, it is often ignored that the ground structure and entrance stair can also affect the user's assessment of underpass safety. Thus, this study uses the photo evaluation method to measure the safety perception of these 2 spatial characteristics. It shows that ground structures can enhance safety perception if top covers transmit light, side structures have higher area ratio of permeability, structures are lightweight, and entrances have larger width; when entrance stairs have higher linking with outside, bigger stair width, visible tunnel end, shorter stair length, and better and warm-toned illumination of stair ends, the sense of security can increase significantly.