1968 年 1968 巻 6 号 p. 189-202
1. Network simulation method as applied to traffic assignment to road-network and to search for optimum road network and its optimum pricing
a. Procedure for traffic assignment to road-network which includes toll-motorways
A network simulation method for the subject purpose is presented. The method builds in its system the congestion phenomena and also the different monetary evaluation of time saving by different people. Congestion as measured in terms of “traffic volume-road-capacity-speed” relationship and the time evaluation as expressed in terms of percentage distribution of different monetary evaluation are quantified based on empirical data.
b. Search for optimum road network and its optimum pricing
Traffic assignment is made to several proposed alternative with different alternative toll rates by the method mentioned above. These alternative proposals are then compared with each other on the basis of the total trip costs incurred as expressed in terms of time cost and vehicle operating cost and the total cost of roading (construction and maintenance) over a certain time span. The one which costs least on the basis states as above is considered for adoption as the optimum road network and optimum toll rates.
Toll rates which will accrue maximum toll revenue to road authority can also be determined by the use of this traffic assignment and cost computation procedure.
2. Road investment criteria and problem of who should bear the cost
The problem of adequacy of the current and contemplative size of total road investment of Japan and adequacy of its allocation among different types and standards of roads, among regions and over time are critically analized. The adequacy must not only be considered in terms of cost-benefit or cost-efficiency angle but also in terms of who should bear the cost and to what extent, this latter angle involving such problems as cross subsidization among regions, among different types and standards of roads, subsidization from outside source, equal footing with other competing transportation modes, and marginal cost pricing versus cost compensating principle. These problems are briefly discussed and some suggestions are presented about Japanese roading policy.