在都會區之公共運輸系統中,計程車屬「副大眾運輸工具」,相較於一般大眾運輸系統,由於可提供私人運具所擁有之方便、迅速、及戶、私密、舒適、營業時間長及免停車等使用特性,在經濟活動頻繁之都會地區廣為旅行者所歡迎,只要費率合理、服務品質優良,即可廣泛吸引私人運具使用者之搭乘,而發揮降低環境污染與提升道路使用效率與安全性等功能。 本研究建立數學模式,推導在最大社會福利目標並考慮預算限制及外部性下,計程車市場之最適與次佳費率與空車率,並進而研析計程車之最佳數量。就理論分析成果而言,本研究建立之模式突破過去研究對於需求彈性之限制,並針對市場最高願付價格及計程車之外部性加以考量,使其應用範圍更加一般化。 而針對台北地區實證分析之研究結果則顯示,當計程車空載時,每延車公里將產生主觀評價約1.2元之外部成本,具有外部不經濟之特性;而當計程車載客時,每延車公里對於全社會將產生主觀評價約0.4元之外部效益,具有外部經濟之特性;而最佳化結果顯示,當需求之價格彈性為-1.4時,計程車之最適空車率約為18.07%;在不考慮損益兩平時之最適費率約為每車公里20元,但須給予乘客每延車公里4.38元之補貼,以彌補計程車業者之虧損;當考慮損益兩平時,計程車之費率則約為24.9元;在每日營業9小時之假設下,不考慮損益兩平限制之最佳解求解結果顯示,台北縣市地區最適之計程車數量為1,335輛,相較於現況之58,488輛,最適計程車營業數量則需較登記數量減少1,786輛,而若加入損益兩平之限制,則次佳計程車營業數量則需較登記數量減少20,337輛;在考慮損益兩平限制下,以目前台北地區之計程車市場而言,只要計程車每日營業里程超過108.15或營業時程超過5.87小時,即有可能出現超額供給之現象。
Taxi is a paratransit in the urban public transit systems. Compared with conventional mass transit systems, because of its convenience, speediness, door-to-door attribute, privacy, comfort, long-time operation, as the private autos but without parking cost, taxi has become a popular mode in the urban areas. If the fare is reasonable and the service quality is high enough, taxi would be very attractive to private vehicle users and hence reduce the environmental pollution, enhance the efficiency and safety of transportation system and, furthermore decrease the external cost of using the private vehicles. In this study, a generalized model with the welfare maximization objective, the budget constraint and the consideration of externalities has been developed and used to analyze for a cruising taxi market. The model has included the effects of externality issue and resolved the common restriction of the conventional log-linear demand function so that the price elasticity has no longer to be less than -1. The numericial results show that the vacant mileage would produce the external cost which is valued as 1.2 NT dollars per vehicle-km while the occupant mileage would contribute the external benefit as 0.4 NT dollars per vehicle-km. If the price elasticity is -1.4, the optimal vacancy rate should be 18.07%. The first-best fare and subsititution rate is 20 NT dollars and 4.38 NT dollars per vehicle-km respectively while the second-best fare is 24.9 NT dollars per vehicle-km. It is also shown that the first-best fleet size of taxicabs in Taipei metropolitan area should be reduced by 1,335 while the second-best fleet size should be reduced by 20,337 under the assumption that the daily average operation hour of taxi drivers is 9 hours. Furthermore, under the second-best environment, it is shown that the taxi market of Taipei metropolitan area would be excessively supplied when the taxi drivers’ average daily operation length was over than 108.15km or the average daily hour was over than 5.87 hours.