第一節 結論
本研究結果顯示在街谷中喬木是影響道路污染濃度的主要因子，這與文獻中 所提及的是相同結果，主要原因為喬木的樹冠阻礙了來自車輛所排放污染物的擴 散。這表示說當街谷污染濃度高時，應減少樹冠的遮蔽，快速讓污染物向較為乾 淨之區域擴散。在灌木配置方面，灌木亦會造成街谷污染濃度不同影響。在一般 街谷及深型街谷中中央分隔島種植灌目是能降低人行道污染濃度，但多數方案中 顯示種植灌木或加高灌木高度污染濃度也隨之提升，造成差異的主要原因取決於 灌木擺放的位置以及跟喬木之間的關係，這需後續研究來說明影響差異的因素。
第二節 建議
經由過去文獻與相關資料進行方案研擬，得到81 種道路植栽配置型態，以 ENVI-met 微氣候模擬軟體進行數值模擬，模擬街谷 24 小時 PM2.5濃度表現，探 討不同道路植栽配置的污染濃度變化。根據本研究結果，提出以下建議作為實務 與研究上的參考。
一、道路植栽設計
依據研究結果，在道路植栽配置時應考慮當地風場環境、盛行風方向、建築 物高度、道路寬度。而本研究建議道路植栽規畫時可針對車流量進行調查，在非 全日高交通量的路段下，應盡可能的提升綠化面積，這對於整體環境品質能有改 善效果。而配合盛行風向，街谷背風面種植葉面積密度較低之喬木。
二、後續研究
從研究結果中發現，增加灌木綠化量會造成污c 染濃度提升，但在少數方案 中發現，灌木、綠籬儼然是改善人行道空氣品質之一項契機。而本研究並未對此 方面進行更多著墨，後續研究建議，可朝往灌木種植的位置、寬度、高度、與喬 木的關係進行討論。
另一是對於境外貢獻源的探討，本研究討論的範圍並不涉及境外貢獻源，如 上文所言，本研究建議後續研究可著墨於當街谷有境外貢獻源時植栽配置與污染 濃度的關係。
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