中文摘要：

为提高公路网对经济社会发展的适应性,针对公路网布局优化问题,从公路网系统功能和经济社会发展角度出发,以建设成本、土地占用机会成本、运输成本、公路使用效率四因素为决策变量,构建公路网综合评价模型。在此基础上,以公路网三点典型结构为支点,提出添加虚拟节点的优化方法,并引入粒子群算法对优化模型进行求解。最后,以关中、陕南地区公路网优化为例,将四因素优化方法的优化效果同传统优化方法作对比分析。研究结果表明：四因素公路网综合评价模型具有良好的评价功能,且评价方法灵活、贴近实际;在三点典型结构中添加虚拟节点的优化方法可行且有效;同传统优化方法相比,所提出的方法能兼顾解决交通拥堵问题和非合理性畅通问题,优化效果显著。

英文摘要：

In order to improve the applicability of road network to economic and social development, aimed at the issue of road network optimization, from the perspective of network systematic goal, and economic and social development, four factors of construction cost, land opportunity cost, transportation cost and road network efficiency were taken as decision variables to build up a comprehensive assessment model. And then, with tri-node typical structure as an example, an optimization method by adding virtual node to the network was proposed and the numerical solution of the method was obtained by particle swarm optimization （PSO） algorithm. After that, road networks of Central Shaanxi and Southern Shaanxi were taken as examples to analyze the optimization effects of traditional methods and four-factor method. The results indicate that the evaluating function of four-factor based comprehensive assessment model is very strong, and the application of the model is flexible and much close to reality; the method of network optimization by adding virtual node is feasible and effective; compared with traditional optimization methods, both of traffic congestion and unreasonable unblocked road can be considered during the process of four-factor optimization, and the optimization is significantly great.