SOCIAL COST-BENEFIT APPROACH TO THE OPTIMAL LEVEL OF ROAD NETWORK AND THE SOURCE OF ITS FUND

在本研究中，我们首先回顾了道路网络研究领域中的社会成本效益方法以及道路融资程序和最佳道路建设水平的研究。根据格林博士及其同事进行的综合研究，交通，特别是公路交通所产生的社会成本应包括非货币性个人（驾驶）、货币性私人（购买汽车）、捆绑式货币性私人（停车）、政府（道路维护）、货币性外部（拥堵）和非货币性外部（空气污染）成本。我们基本上遵循了格林博士提出的分类。第二，我们选择仙台市作为我们的研究区域。我们应用我们的软件和社会成本效益的方法，在仙台市的实际情况，研究道路建设的最佳水平。我们发现，与时间成本相比，环境成本在社会总成本中所占的份额并不高。并对交通需求、现有路网、道路建设资金需求之间的平衡性进行了评价。第三，分析了道路交通噪声污染成本的分布。我们评估了道路收费和道路建设等几项政策的有效性。最后研究了公路网等级与公路资金来源的适度平衡问题，并提出了进一步研究的方向。

In this study, first we reviewed several studies on social cost-benefit approach in the field of road network research as well as procedure of road funding and optimal level of road building. According to the comprehensive study conducted by Dr.Greene and his colleagues, social costs incurred by transport, especially road transport, should cover non-monetary personal (driving), monetary private (purchase of a car), bundled monetary private (parking), governmental (road maintenance), monetary external (congestion), and non-monetary external (air pollution) costs. We basically followed the categories proposed by Dr.Greene's.Second, we selected Sendai City as our study area. We applied our software and social cost-benefit approach to actual situation in Sendai City and studied the optimal level of road building. We found that the share of the environmental costs out of the total social costs was not high as compared with time cost. We also evaluated the balance among travel demand, existent road network, and road fund required.Third, we analyzed the distribution of the cost of road traffic noise pollution. We evaluated the effectiveness of several policies such as road pricing and road building. Finally we studied the appropriate balance between he level of road network and the source of road fund, and proposed the directions of further studies.