旅運需求與迴車時間變異對國道客運排班與車隊影響之研究

Abstract

過去有關大眾運輸排班問題最佳化的研究，大都以整體系統的觀點來衡量，較少站在營業者的角度進行討論；前者可在旅運需求固定的前提下，以追求營運者的營運成本與乘客的旅行成本最小化為目標；而當考量彈性旅運需求時，則以營業者的獲利與消費者剩餘最大化為目標。 惟就營運者而言，其營業獲利高低與實際所載運的乘客數以及營運成本有關，過去的相關研究在處理乘客的旅行成本或是消費者剩餘時，大都將乘客的車外等候時間、車內旅行時間、以及步行距離以時間價值換算為金錢成本納入系統考量，對於追求營業獲利最大的營運者而言並不容易接受與應用。此外，由於目前政府已開放國道客運市場的經營權，同一條路線不限一家業者經營。業者在班距排程作業上，除了要考量乘客會因為班距過長而不願搭乘外，還需將競爭對手所提供的服務納入考量。因此，過去的分析方式並不完全適合目前的經營環境。 本研究採用數學解析性方法，以營運者利潤最大化為目標，在考量競爭對手對乘客的吸引因素與車輛容量限制等的前提下，探討迴車時間變異程度與旅運需求的時間變異特性對於發車班距、車隊規模、業者獲利的影響。 在處理旅運需求時間變異特性方面，本研究採行多時段班距的排班作業方式，並針對整個營運時段的切割方法、不同的時段長度、以及個別時段內乘客抵達率的訂定進行探論；在迴車時間變異方面，主要討論迴車時間長短與變異程度對業者所須準備車隊規模的影響，推導固定迴車時間與迴車時間具有變異性時的車隊規模計算方式，並在系統架構中將車隊成本納入考量，以作為制訂發車班距與調整服務車隊規模的決策依據。

Previous research on public transport fields has focused much more on scheduling optimization problems from a system-wide viewpoint than from an operator side. The former would set a goal of either minimizing the total system cost based on a fixed travel demand or maximizing the social welfare as the demand variability is taken into account. As for the latter, unfortunately, there were few studies concerning the issue of ways to maximized benefit for transit operators under a competitive market share environment. Practically, the earned profit for transit operators is relevant to riderships and some kinds of operating costs. For simplifying cases, most studies in the past years would presume some associated time values to estimate riders' travel costs (e.g. waiting cost, in-vehicle cost, and walking time cost) or consumer's surplus. However, this is quite impractical to transit operators, as they should evaluate not only the riders' costs but the variability of market share due to a favorable strategy from any competitor or an unreasonable scheduling decision. Besides, the recent highway deregulation policy has allowed many common carriers to share the highway transit service market. Thus the previous studies were found not well applicable to the existing operation environment. A series of formulation that analytically sets an objective of maximizing profi for transit operators have be developed in this study. With the consideration of rider's mode choice among competitors and capacity constraints to transit buses, this study explored the corresponding headway settings, operators' benefit, and fleet size etc. based upon the temporal variation of travel demand and the variance of bus circulation time. With regard to the time variance for feeder buses, this study mainly focuses on the way of renewing fleet size timely in order to maintain a higher bus schedule adherence. As for the temporal variation of travel demand, a multi-headway approach seeking to concurrently optimize the cutting periods and the service headways via the arrival information for each specified interval is proposed. The excessive fleet cost is also considered in the formulation so that the transit operators can make an optimum fleet decision that meets different requirements. Finally, the conclusions and recommendations have induced in the text.