城市交通网络中相继故障问题的研究

为了探讨城市交通网络拥堵产生机理，在分析城市交通网络特性的基础上，建立了双层城市交通网络模型，构建了交通动力学模型，并引人累计到达目的地的车辆数目和网络瘫痪时刻2个参数来刻画交通网络拥堵相变。通过计算机仿真，分析了网络拓扑结构、车辆生成率、道路交叉口能力和网络规模对网络拥堵相变临界值的影响，运用车辆到达数目对时间的导数将网络划分为自由流、亚拥堵和瘫痪3种状态，并给出了对应的区间值。研究表明，对于随机出行网络和无标度出行网络来说，都存在自由相到拥堵相的相变，相变点的值可以用来衡量网络能力，且车辆生成率、交叉口能力和网络规模对网络能力有着不同程度的影响。

Cascading Failures on Urban Traffic Networks

In order to further investigate the mechanism of traffic congestion in urban traffic networks, a hi-level network model was established based on analyzing the characters of urban traffic network, in which the lower level repre- sented road network and the upper level represented trip network. A traffic dynamies model was built and two parameters were introduced for studying the phase transition in traffic networks. The two parameters were the cumulative number of vehicles which had reached their destination and the moment when the network was paralyzed separately. The effects of network topology, vehicle generation rate, intersection capacity and network scale on the critical value of congestion tran- sition were analyzed through computer simulation. The network was divided into three states （free flow, next to eonges- tion and paralysis） by means of the derivative of arriving number with respect to time. Moreover, the corresponding inter- val value was given. The results show that for both random and scale-free trip networks, there exists a phase transition from free phase to congested phase and the value of transition point can be considered as a measurement of network capaci- ty. Furthermore, there are varying effects of vehicle generation rate, intersection capacity and network scale on network capacity.