An Impact Study on Highway Transit Scheduling and Fleet Size with Travel Demand Patterns and Circulation Time Variation
|關鍵字:||國道客運;排班作業;車隊規模;Highway Transit Services;Bus Scheduling;Fleet Size.|
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.
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