本研究之主要目的在於探討都市街道中地平面、頂面及垂直面等空間性質所形成之關係，並探討這些空間性質對於街道環境封閉感之影響。為探討此關係性，本研究以台北地區街道空間作為研究對象，透過拍攝實際街道景觀照片做為施測媒介，以繪圖軟體分別抽取街道立面之人工建物、植栽、街道平面之地面、與街道中可見之天空等因子，分別計算其面積。另外請受測者評估照片中街道景觀空間封閉感受程度。分析各項空間因子和街道空間封閉感之關係，結果顯示空間組成因子中天空面積與空間封閉感為顯著負向相關，建築物和植物面積與空間封閉感為顯著正相關。應用複迴歸分析綜合建立街道景觀空間封閉感預測模型，並比較各因子對於空間封閉感受之相對影響程度，可得知立面中的植物面積與人工建物面積越大，空間封閉感受越強，惟植物面積對於空間封閉感之影響程度約為人工建物面積之一半。本研究結果顯示，街道景觀中植物部分是較為軟性之空間阻隔物，可減少人工建物所造成之空間封閉感受。因此未來在有關街道景觀之管制方面應多鼓勵增加植栽或立面綠化，以提昇都市街道之景觀品質、改善都市街道空間感受。

This study investigates the relationships among space characters (base plane, overhead,and verticals) in streets and examines the effect of these characters on enclosure of urban streetenvironments. Streetscape photos in Taipei City, the study site, are used to analyze relationships.The area percentages of sky, man-made structures (buildings), plants, and roads in each photo aremeasured. Streetscape photos are also used to survey perceptions of streetscape enclosures. Analyticalresults show that streetscape sky negatively affects enclosure perceptions and buildings and plantspositively affect enclosure perceptions. Regression analysis results show that the positive effectof man-made structures is almost double the effect of vertical plants on enclosure perceptions. Weconclude that plants in streets have softer space characters than buildings. Study results suggest thatplanting on streets should be encouraged to improve the quality of city street spaces and streetscapes.