竹内 健蔵

わが国の都市高速道路は償還主義の下で徐々に整備されてきており、一定のネットワークを形成しつつある。OD間で複数の経路がある場合、その料金の設定によっては混雑問題や環境問題が激化する可能性がある。本論は、道路の規模を変数とする長期の料金設定について、ネットワークを考慮に入れて分析することを目的とする。モデルによる考察の結果、社会的純便益を最大にする最適料金水準で実現されるネットワーク均衡量において、各ルートの料金収入の総額はその道路の建設の総費用と等しいことが明らかになった。ただ、ルートごとの収支均衡がそのまま最適な道路交通量をもたらすものではないことに注意するべきである。Urban expressway in Japan is gradually realizing a certain level of network under the principle of cost recovery. There may be the possibility that congestion and environmental problems become worse depending on the road user charges in the case that there are several routes between an origin and destination. In this paper, optimal road pricing in the long run is analyzed taking the optimal road scale and the optimal road network equilibrium into consideration. Wardrop principle is explicitly incorporated into the model. It is cleared that total revenue in each route is equal to total construction cost in its own route under the optimal network equilibrium in which social net benefit is maximized by optimal road user charges. However, it should be noted that a naïve achievement of break-even point in each route does not lead the optimal traffic volume in the optimal network equilibrium.

記事分類: 産業--運輸・通信--陸上運送

The evaluation of benefits occurring by transport investment is very important in cost-benefit analysis. It is, however, considerably difficult in terms of calculating each item of benefits practically. These difficulties seem to be classified into two problems: (1) In what stage should the benefits be estimated? And (2) How should changes of the benefits in the other route or area, which derived from transport investment in out route or area be evaluated? In order to answer these questions, it is useful to classify transfer of benefits by transport investment into vertical and horizontal transfer of benefits. Vertical transfer of benefits focuses on relationship between stages of transfer of benefits. It is shown that vertical transfer of benefits is pecuniary external economy and it is proved explicitly by simple diagrams that pecuniary external economy does not distort optimal resource allocation. Since the existence of factors causing market failure obstructs 100 percent transfer of benefits from road users to consumers, it is desirable that benefits by transport investment are evaluated at the earliest stage such as road users’ benefits. The analysis of horizontal transfer of benefits makes it clear that occurrence of benefits in on area may be closely connected with decrease of benefits in the other area and, therefore, it is shown that the evaluation of benefits in only one area may make cost-benefit analysis inaccurate. If the distribution of benefits by transport investment is an important factor in transport project appraisal, it will be possible to include the distributional effect of the project in an analysis. However the analysis includes strong value judgements and is no longer a “cost-benefit analysis,” which is established to attain economic efficiency in a true sense.

記事分類: 産業--運輸・通信--陸上運送