本研究主要考量政府管制的立場，並從業者營運效率的觀點，在路線營運成本最小之前提下，利用Translog成本函數探討各路線捷運接駁公車之成本效率；在成本函數構建中，本研究設定之產出係為路線長度與班次數之乘積，而班次數即為一可反映出需求因素的替代性變數。此外，在公車路線成本模式中，本研究加入與路線營運特性相關之屬性變數(即營運路線長度)，以及相關虛擬變數(如路線彎繞、公車專用道、停靠站數等)，藉以探討各變數與成本變動之關係。。最後，本研究透過最小有效規模(Minimum Efficient Scale )之經濟概念下，估算台北市各捷運接駁公車路線之理想營運路線長度，並進一步探討產出與班次數之變動。
在MES分析方面，本研究利用平均絕對偏差百分比(Mean Absolute percentage of bias, MAPB)值衡量原路線長度與理想路線長度(即MES之估計值)間之差異程度，計算結果整體捷運接駁路線之平均MAPB值為21.98%，並發現各捷運接駁路線之平均路線長度大致尚有2.16~3.97公里之調整空間;而在台北市捷運接駁公車路線之平均營運條件下，經由MES估計所得之各捷運路線接駁公車之最適路線長度則介於15.68~18.99公里之間。上述所有結果除可供公車業者調整路線營運里程之參考外，亦可做為市政府審議並管制其路線長度之依據。
After the operation of MRT system of Taipei city, the bus transit is still the major part of the public transit system, and plays a complementary role for feeder service in MRT corridor. At present there are 45 lines of feeder bus, which are planed by the Taipei city government to operate cooperatively with the MRT system. . Regarding to the setting of route length, the 8~10 kilometers of O-D trip are set as the principle for feeder bus. But this rule is only a experience judgment, and there is no theoretic base. In practice, some of the bus operators always try to lengthen the route or reduce the bus station in order to reduce the cost , that already lose the original meaning of providing feeder bus. Therefore, It is an importance common topic to build the reasonable principle of setting the length, and to considerate the carrier’s position to pursue the minimum cost for the government and the bus operator. .
In the position of regulation of government and the viewpoint of operator’s efficiency, the Translog cost function is employed to explore the cost efficiency of feeder bus under the minimum operation cost of route. In the building of cost function, the output is set the multiplier of the route length and frequency, where the frequency can be treated as a variable reflecting the level of demand. Moreover, in the cost model of route of bus, the attribute variable related to the characteristic of operation of route (i.e. length of route), and the related dummy variable (such as curve of length, the bus exclusive lane, and the number of bus stop) are utilized to explore the relationship among the cost and these variables. Finally, the economic concept of Minimum Efficient Scale (MES) is applied to estimate the ideal operation length of each route of MRT feeder bus in Taipei city. Beside, the changes in output and frequency are also further explored.
The 129 samples of route during the period of 2002~2004 years are used to establish the total cost function of MRT feeder bus. The empirical result shows that the bus exclusive lane has positive influence in operator’s cost, and the more number of stop will indeed increase the operation cost of route via the estimation result of the dummy variable of characteristics of route. In economics of scale, some of route of feeder bus posses the increasing or decrease return to scale, this means some of them can be adjusted to the optimal economics of scale by adjusting of frequency.
In the analysis of MES, this study adopts the Mean Absolute Percentage of Bias(MAPB) to measure the degree of difference between the original length of route and the ideal one(i.e. the estimated value of MES). The consequence of calculation indicate the average MAPB is about 21.?% in the total routes of feeder bus, and find there are average value of 2.16-3.97 kilometers of route lengths to be adjusted among each MRT line feeder bus. Beside, the optimal lengths of route of feeder bus are in the range of 14.5-18.99 kilometers for each MRT line, via the estimation of MES, under the average conditions of operation of MRT feeder bus of Taipei city. All of the above results can be referred as adjusting and regulating on length of route of MRT feeder bus for the bus operator and the government of Taipei city