都市街道景觀設計元素之成本效能研究

Study on the Cost-effectiveness of the Design Elements on Urban Streetscape

本研究分別由經濟與心理偏好觀點評估街道景觀計畫，並分析設計元素包括植栽、人行道舖面對景觀偏好及效能影響之相對重要性。研究方法以電腦模擬台北市街道作為背景，景觀元素選取不同成本或不同種類之行道樹種類、種植距離、灌木高度、人行道舖面材質、舖裝型式、舖面色彩，共組成32個街景替選方案，問卷受測者包括學生和景觀專業者，學生以條件評值法、景觀專業者以條件評估法設計問卷。在替選方案的經濟評估中，將景觀美質偏好程度視為方案設計之效益，並與各方案之材料成本做比較分析，本研究使用六個指標評估街道景觀的經濟價值，包括由條件評估法獲得之可接受成本，其他指標則關於成本及效益（成本C、景觀偏好P、可接受成本AC、P／C、AC／C、AC－C）。研究結果顯示，行道樹種類、灌木高度、舖面材質、舖裝型式、舖面色彩組合不同對景觀偏好、及成本效能皆有影響，行道樹種植距離影響較小，而受測者於評估經濟價值時會同時考慮景觀美質與成本價格，指標中AC－C與低成本計畫高度相關，而P／C是較適合於高景觀偏好與低成本之平衡指標。 This study assessed streetscape plans from both economic and psychological points of view and analyzed the relative importance of design elements such as street vegetation and sidewalk pavements on the economic and preference-based values. The research conducted experiments by using computer-simulated images as virtual alternative of street design projects in Taipei City. The elements selected various types of design with a varying cost of street trees species, interval of trees, height of shrubbery, material, pattern and color of sidewalk pavements. The respondents participating in this experiment were asked to evaluate thirty-two alternatives by two kinds of questionnaires, contingent rating method was for students and contingent valuation method for landscape professions. In the economic evaluation of alternatives, the availability of landscape esthetics preference were seen as benefits, and these can be compared with the material cost of an alternative. This study used six indices for the economic evaluation of street design that include an acceptable cost derived from a contingent valuation method and composite indices related to the cost and benefits(cost(C), preference(P), acceptable cost(AC), P/C, AC/C, AC-C) and clarified their characteristics indicating cost-effectiveness. The results indicated that street trees species, height of shrubbery, pavements material, pavements pattern, pavements color of sidewalk would influence preference and cost-effectiveness. The respondents considered both landscape esthetics as well as material cost when they evaluated economic values of streetscape. In addition, the results suggested that AC-C is highly correlated to low cost plans and that P/C is a moderate index balancing high landscape preference and low cost.