道路投資最佳時機之探討

The Optimal Timing of Road Investment

黃雅訢(Yah-Sin Huang)

指導教授 ： 蔡智發

國立臺北大學/公共事務學院/都市計劃研究所/碩士(2016年)

摘要

本研究為探討一條需求持續成長的道路建設之最佳投資時機。由於道路需求持續成長，將使每年之交通流量、使用成本與效益上產生變化，因而有別於以往之研究，於評估投資時機主要以評估年期之總淨效益極大化為目標，淨效益為道路使用者的總效益扣除使用者的總成本與道路投資之成本，而不同年期則經年利率換算為現值計算。
本研究將使用成本效益分析方法，建立理論架構之模型，其中，需求成長函數則分別以線性成長及修正指數成長兩種模式，探討政府是否課徵擁擠稅社會淨效益最大的目標下之最佳投資時機，並應用研究模型以實際道路投資案例進行討論。
研究結果顯示，若投資時間太早，雖可以避免後續擁擠而衍生的使用者成本，但由於投資興建成本太大，使其社會淨效益變小; 而若投資時間太晚，雖可以避免投資興建成本過大的問題，但由於需求旅次增加，道路擁擠，使用者的成本隨之增高，亦造成社會淨效益下降，顯示期間存在ㄧ邊際效益等於邊際成本，而可達到最大社會淨效益之時間點，即為該路段最佳投資時機。

關鍵字

交通建設投資 ； 道路 ； 成本效益分析 ； 最佳投資時機 ； 擁擠稅

並列摘要

This study is to explore the best investment timing in a transportation corridor with a growing traffic demand. As the traffic demand continues to grow, the traffic volume, costs and benefits will vary annually. It is different from the previous studies that my study is to evaluate the optimal timing of road investment by achieving the goal of maximal total net benefits, measured by the trips’ total benefit minus the trips’ total cost and the investment costs.
The model is developed by using the method of benefit-cost analysis at first. Two types of demand function including a linear growth function and a modified exponential growth function are employed to explore the optimal timing for road investment under the condition with or without a congestion tax. The model is then applied to the real case of a transportation corridor in the Taipei metropolitan area.
It is shown that if the investment is too early, it can avoid the higher road users’ costs due to traffic congestion but the investment costs tend very high and thus decrease the social net benefit. If the investment is too late, though it can avoid the problem of high construction costs, the high travel demand incurs road congestion and high road users’ travel costs, and decreases the net social benefits. It shows that there exists a timing which can reach the maximal social net benefit when the marginal benefit is equal to the marginal cost. That is the optimal timing of road investment.

並列關鍵字

Road Transport Investment ； Cost-Benefit Analysis ； Investment Timing ； Congestion Road Pricing

參考文獻

行政院公共工程委員會 (2003)。公共建設工程經費估算編列手冊。行政院公共工程委員會。

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