廢棄物清運績效綜合指標

Abstract

廢棄物清運是廢棄物管理中重要且佔總經費比例最大的項目，故有必要評估清運績效以提昇效率。過去評估方法中除問卷評估外，亦有以個別清運績效指標評估或使用資料包絡分析法（Data Envelopment Analysis，DEA）分析。個別指標雖簡單明瞭易計算，但往往針對單一面向評估。DEA可辨別出單或多因子中較有效率者，但各受評對象以不同權重來評估，雖曾有研究提出方法依DEA結果求取共同權重，但由於會得到多個不同權重組，而不易選出合適的一組。此外，人口分佈、道路密度等因子均具有空間差異，會影響績效及導致評估結果不公平，然而過去評估績效的研究中很少考量到空間性差異，亦無適當的方法可直接引用。本研究因而以全省各清潔隊為案例發展一套適用於國內的廢棄物清運績效綜合指標。 由於各清運績效指標適用的評估範圍不同，有必要建立一套篩選清運績效指標之方法，本研究因而依據指標目的符合度、計算難易度、適宜性、完整性、相似度、鑑別度等五項準則建立一套程序。篩選適合評估鄉鎮市清運績效的指標。共選出單位清運量成本指標、單位車時清運量指標、單位車輛清運量指標、單位職工服務人口數指標、單位里程清運量指標等五個指標作為建立綜合指標的子指標。進而以共同權重法為依據，且訂立鑑別度、不能忽略主要指標、相似性及偏斜性等四項原則作為篩選依據，求取一組適當的共同權重建立綜合性評估指標。最後，針對空間性差異導致績效評估不公平或不適宜問題，本研究以加入空間性因子，及訂出中性因子作為修正指標公平性的基準，建立一套能考量空間性因子的清運績效綜合評估指標，以供各環保機關做更適宜的績效評估。

Municipal solid waste collection (MSWC) is a major and expensive task for a local waste management authority. Assessing the performance of collection practice for promoting MSWC efficiency is thus important. Beside the questionnaire survey, two methods are frequently applied for performance assessment: a key performance (KP) indicator and data envelopment analysis (DEA). A KP indicator, although simple and generally easy to understand, usually can assess only one single aspect or factor that is not enough to assess the overall performance. DEA can discriminate relative effectiveness, but it uses different weight sets to assess individual groups and is thus impractical. Although, for overcoming this problem, a method proposed by a previous study can generate a set of comment weights, it is not easy to choose an appropriate weight set from many alternative sets. Furthermore, spatial factors such as population distribution and road density can significantly affect the performance of MSWC, and if they are not properly evaluated, the performance assessment may be unfair to some groups. This study was thus initiated to develop an aggregate indicator that is suitable to assess the MSWC services provided by local governments in Taiwan. Available data for MSWC services provided by 307 Taiwan local governments were collected. Related indicators obtained from various sources were analyzed for their applicabilities in assessing MSWC performance efficiency. Six criteria were created and used to evaluate the applicability of an indicator: purpose match, measurement difficulty, adaptability, completeness, similarity and discrimination. An aggregate indicator was then developed based on five major indices: cost per MSWC quantity, MSWC quantity per unit collection time, MSWC quantity per collection vehicle, served population per collector, and MSWC quantity per vehicle mileage. The DEA method was used to analyze relative efficiencies of all local governments. A method modified from a previous approach was applied to generate a set of common weights for all five major indices according to the DEA results and four major rules: discrimination, no exclusion for any major index, similarity, and skewness. To resolve the fairness problem caused by spatial differences, three spatial factors of population density, road density, and waste generation density were evaluated, and subsequently a new aggregate indicator was proposed. The procedure proposed herein is also applicable for developing a similar aggregate indicator for other problems.