中文摘要：

考虑到现实二维路网中的立体交叉特性,本文在经典Biham-Middleton-Levine（BML）模型的路网结构中嵌入了一些典型的立交桥构型.通过改变立交桥的数量、分布构型,拓展了BML模型,以研究立交桥对路网交通流的整体影响.数值模拟表明,随机分布的立交桥构型,即盲目修建立交桥,在立交桥比例较低时,会对路网整体运行性能产生负面影响——加速拥堵.进一步将立交的分布进行适当地组织,形成真实反映城市路网特征的立交构型,如环形、方形.模拟发现,特定立交比例下方形立交构型对系统产生正面的影响,使得系统平均速度整体上要明显高于随机投放立交的状况;而环形立交构型投放至网络中,使得全局性堵塞提前发生,反而不能提高网络交通流的运行效率.这些结论虽与传统认知相悖,却具有较强的现实指导意义.

英文摘要：

Considering the widely existed grade separations in the two-dimensional urban road network, this paper incorporates some overpass configurations into the classic Biham-Middleton-Levine （BML） model, which has not yet been fully investigated. With the change of the overpass＇ s quantity and its configuration, the effect of overpass on the network performance is discussed based on the extended BML model. Using the numerical simulation, it is found that overpass newly built but without deliberate and reasonable plan, could only aggravate the existing congestion conditions, if the overpass ratio is low. Furthermore, the configurations of grouped overpass, which could reflect the realistic characteristics of overpass distribution in the road network, such as squared and loop-shaped configurations, are incorporated into the network. It is found that the squared configuration would bring positive effects on the network flow, while loop-shaped configuration bring negative effects on the network flow under certain conditions. The simulation results overthrow the conventional perception and have the extensive applicability and practical significance.