基於移動污染風險潛勢指標之低污染公車補助路線優先性分析

Abstract

為提升空氣品質，補助推廣低污染公車為改善移污的策略之一。由於 全面更換低污染公車的成本頗高，為使補助經費能有效改善空氣品質，有 必要探討各公車路線更換低污染公車之優先性。 本研究因而依據移污濃度及其對沿線人口的影響程度建立指標評估 台北市各公車路線替換低污染公車的優先性。由於台北市公車路線眾多， 故本研究首先訂定初選原則刪除影響較小之路線。然後以OSPM 移污街谷 模式依據各街道交通流量、沿線建築及氣象特性等因子模擬各街道之污染 程度及推估其空間分佈。然後依據移污濃度以及對沿線人口的影響建立污 染濃度-長度及吸入風險二組指標，首先建立單一污染物的指標，然後再依 據RELA 及空氣品質標準為基準建立可供用以比較不同污染物影響程度的 指標，且進一步加總各污染物子指標建立綜合指標，以作為評估各路線補 助優先性之依據。 初選時共刪除路線75 條，再依據行駛里程選取前100 條路線進行後 續分析。由各路線OSPM 模式模擬結果可看出移污濃度主要受道路寬度、 高度以及車流量影響較大。指標優先性分析方面，由於評估時有必要考量 對居民及活動人口的影響，故本研究建議採用吸入風險組的指標。單一污 染物子指標中CO 和PM10 及PM2.5 子指標間相關性頗高，其餘子指標間的 相關性則不高，單一污染物子指標可考量採用PSI 指標污染物PM10 或是 與其相關性頗高的CO 子指標。唯只考量單一子指標評估較不全面，且因 不同污染物所產生之影響不同，故本研究建議亦可考量採用綜合指標。

For improving ambient air quality, subsidy for low emission buses is a widely adopt policy to reduce mobile source pollution. Since the cost for replacing buses with low emission vehicles is quite high, prioritizing bus routes for increasing the effectiveness of the subsidy policy is thus desired. Therefore, this study establishes indicators to evaluate the subsidy priority of a bus route according to simulated pollutant concentration and affected population along the route. Since there are too many bus routes in the studied area, Taipei City, this study excludes those routes with obviously low pollution impact first. Then, the Operational Street Pollution Model (OSPM) is applied to simulate the mobile source pollution along each route based on estimated traffic flow, buildings on both sides, and meteorological data. Two sets of indicators are established. The first set is computed according to pollutant concentration and route length, and the other is based on the estimated pollutant intake sum by affected population. Indicators for individual pollutants are established first. For comparing the results obtained for different pollutants, the Acute Reference Exposure Level (RELA) and Air Quality Standard are applied to establish the other sets of indicators. Finally, aggregate indictors are set up by adding up all indicators for individual pollutants. The applicability of each indicator for prioritizing bus routes for subsidy is then evaluated. Seventy-five routs with obviously low pollution impact are removed during the initial screening procedure. For the rest of routes, according to the trip length of each route, the top 100 routes are selected for further analyses. The results simulated by OSPM are mainly affected by street width, building height, and traffic flow. Because the impact on affected population along a route should be considered, the intake-sum indicators are thus recommended for prioritizing bus routes. Although the CO, PM10, PM2.5 indicators are highly correlated, others are not. For individual pollutant based indicators, either the PM10, as the major PSI critical pollutant, or CO indicator is suggested. However, different pollutants have varied impacts on human, and the indicator based on one individual pollutant may not represent the overall effect from all pollutants. The aggregate indicator is therefore recommended for prioritizing bus routes for low emission vehicle subsidy.