臺灣地區縣市空間緊湊發展特性與交通運輸耗能關係之初探

A Research of the Urban Compactness and Transportation Energy Consumption

「緊湊都市」的推動，邁向都市節能永續，為都市計劃界所倡議。然而，部分研究提出緊湊都市不必然能達到節能永續，甚至可能產生相對耗能情形。本文奠基於此議題，彙整都市緊湊節、耗能研究，並以交通運輸作為都市耗能研究標的，分別就大尺度臺灣各縣市與小尺度高雄都會區各鄉鎮區，研提都市緊湊發展特性對於都市交通運輸耗能影響力假說，藉由迴歸分析的曲線估計模型解構都市緊湊特發展性與都市交通運輸能耗關係消長變化。驗證分析結果顯示，儘管高密度特性減少總旅次長度，惟過高的發展密度亦會產生交通擁擠，進而導致行車速度下降、旅次時間與尋車位時間的增加，且運具選擇的偏好可能導致高密度對於大眾運輸比例的影響不顯著。而混合使用對都市交通耗能呈現倒N型三次方曲線，顯示當土地混合使用超過一定門檻時，過度混合使用反而減少旅次數量。是以，節能永續之都市緊湊發展型態，必須顧及緊湊度指標與交通運輸系統的配套措施，合宜的都市緊湊程度與零交通擁擠成本，方能落實緊湊城市達到節能之效果。

Compact city has been promoted by urban planning profession and been regarded as sustainable energy saving strategy. However, some studies refer energy over consuming to compact city strategy. This study investigated energy efficiency and consumption in the transportation sector and further address hypothesis of the potential impacts of compact city on urban transportation energy consumption in Taiwan cities and Kaohsiung townships. A curve estimation model is then used in regression analysis to explore the variation of urban compactness on transportation energy consumption. Although high population density decrease total travel length, over dense urban environment results in crowded and further reduces driving speed and raises up travel time and parking cost, and the preference of transportation might not promote the usage on public transportation under high density situation. Additionally, the impact of mixed use on transportation energy consumption can be depicted as an inverted N type cube curve, which is implied that over mixed use will reduce travel amounts. Therefore, an energy-saving compact city must consider both compact city indicators and a set of transportation system indicators. In fact, the energy saving effect will be achieved by appropriate urban compactness and zero transportation crowded cost.