台北捷運系統成本函數及經濟特性之研究

Abstract

運輸系統的永續性可由「環境」、「社會」、「經濟財務」三個面向衡量。捷運系統的外部效益和社會公平性皆明顯高於私人運具，在「環境永續」和「社會永續」兩個面向具有絕對的優勢。但捷運系統建設成本高昂，台北捷運系統已通車路網76.6公里，實際營運長度74.4公里。初期路網總預算4417.69億元，已通車路線總工程發包金額高達2,126.68億元，平均每公里工程造價約為28.58億元，龐大的建設成本造成營運者和政府單位財政上的困難。就營運面而言，台北捷運公司2006年稅後純益7.96億元，但自2010年起需開始支付第二階段路網自償性財源，平均每年需支付約26億元的償本利息，此一支出未來可能造成捷運公司的財務壓力。因此就「經濟財務」面而言，需審慎評估台北捷運的營運狀況及最適路網規模，提昇資源運用的效率。本研究建立台北捷運系統Translog成本函數，以1996至2006年的營運季資料做計量分析，利用校估後的成本函數分析台北捷運系統的各項經濟特性，包括：要素價格成本彈性、要素使用情形、成本產出彈性、規模經濟、邊際成本、平均成本、最小效率規模。實證研究結果顯示，台北捷運具有明顯的密度經濟特性，要素使用具有僵固性的情形，且要素之間的替代性和互補性偏低。在最小效率規模方面，台北捷運短期營運的狀況下，不具有最適路網規模，意即不論路網長度為何，運量增加皆可降低平均成本；在長期營運所有要素皆可變動的情況下，當路網長度140公里，季運量為2億1千2 百萬人時，相當於日運量236萬人時，為台北捷運系統的最小效率規模。運量和路網長度高於最小效率規模時，會產生規模不經濟之情形。因此應仔細評估後續路網的必要性，旅運需求量不高的路線，可考慮以輕軌系統、公車捷運系統等其它大眾運輸系統替代，以達到「經濟財務永續」的目標。

The sustainability of transportation system can be evaluated by three indicators: Environmental Sustainability, Social Sustainability, as well as Economic and Financial Sustainability. Compared to private motorized transportation, mass rapid transit (MRT) has absolutely better performance on Environmental Sustainability and Social Sustainability. However, the capital cost of MRT is significantly higher than other public transportation systems. The construction cost of Taipei Mass Rapid Transit (TMRT) amounted to 2.8 billion dollars per kilometer. The huge capital investment may cause to the financial problems of the operator and government. For the aspect of operating, the self-liquidating capital cost of the second stage of TMRT will become the financial pressure on Taipei Rapid Transit Company (TRTC). Therefore, in order to reach the Economic and Financial Sustainability, the operating performance and the optimal network scale of MRT should be evaluated seriously. This study aims to analyze cost characteristics and minimum efficient scale (MES) of TMRT based Translog cost function. The data used in this study is obtained from TRTC for 1996-2006 seasonal operating data. By the estimated Translog cost function, one can analyze the economic characteristics of TMRT. The result indicates that TMRT has strong characteristic of economies of density, and the elasticity of substitution is not significant. For the MES analysis, it is shown that MES occurs when the network length is 140 km and the average ridership is 2.36 million trips per day. This implies that the government should evaluate the necessity of the expanded routes of TMRT. To reach the Economic and Financial Sustainability, other public transportation system, such as light rail and bus rapid tansit, could be considered as another option for some expanded MRT routes with lower demand.