以模糊規劃法求解路網投資決策之效率與公平課題

Abstract

為使國土區域得以均衡發展，在進行公路路網投資決策時應同時兼顧效率與公平的課題。然而以往的相關研究多偏重效率卻忽略公平，因此本研究乃以發展一套實用且兼顧效率與公平的路網投資決策方法為目的。 在路網投資時，應提供各區域主要都市的民眾到該區域中心之合理可及性以滿足生活所需。由兼顧效率與公平的觀點，不僅要針對各主要都市至區域中心的可及性予以最佳化以達成旅運成本的效率，亦需同時令各區域內都市間該項可及性的差異及區域間該項可及性的差異最小化以達成水平性與垂直性的公平。基於此觀念，本研究首先提出多目標之基本型模式，再予以改良提出修正型模式以使得公路投資決策程序更為合理與實用。 本研究以西部台灣公路網為例，以上述模式進行多種情境之示範操作與分析。決策者或管理者可藉以了解在不同的總經費預算、預期行駛速率水準、路段改善的互補關係與互斥方案等各種假設下對公路投資的影響。經由模糊規劃法求解案例研究中之多目標模式，皆可有效獲得兼顧效率與公平的妥協解。 本研究亦探討公路投資預算分配的公平課題，其方法是在模式中依據各都市的社經特性給定預算的比例上限作為其限制式。此外，為擴充修正型模式的使用彈性，亦探討模式中可及性指標的替代方案如旅運需求的消費者剩餘。最後亦嘗試將模式中的公平目標式予以簡化，提出旅運時間標的模式與旅運速率標的模式。並以時速六十公里為標的，示範給定多目標妥協度下最小預算之求解，以符決策程序之需要。

To facilitate equal regional development, the decision-making of highway investment should consider not only cost efficiency but also issue of equity, which is seldom mentioned in past researches. The goal of this research is to develop a practical method for highway investment decision-making to deal with the issues of both efficiency and equity. In highway investment, we should provide people reasonable accessibility from every main city in every region to the regional center. We could optimize the accessibility for main cities in view of efficiency, and simultaneously minimize the difference in accessibility for main cities in the same region and to minimize that difference among regions to maintain both horizontal equity and vertical equity. Based on this concept, the basic model with multi-objective formulation was proposed first in this research and then modified as a revised model to make the decision-making process more reasonable and practical. Case studies of highway investment for western Taiwan were formulated in both models with different scenarios to show the impact of assumptions in future travel speed, total budget, complementary property among links, and exclusive property among alternatives. Using the fuzzy programming, the revised model effectively yielded the compromised solutions for all the cases in view of efficiency and equity. The research also covers the equity in budget allocation among cities, which was processed by restricting the upper bound of the budget share for each main city according to its socio-economic attributes. Besides, to expand the revised model for more flexible use, alternative travel cost/benefit measures were discussed and consumers’ surplus in elastic travel demand was proposed for the future study. For the simplification of objectives in equity, the travel-time target model and travel-speed target model were proposed with alternative equity measures. Furthermore, for the travel-speed target model with a target of 60 km/hr, each minimal budget was obtained in terms of given compromise grades to demonstrate the advanced decision-making process.