Urban traffic system is important for the convenience and efficiency of people’s daily life. The understanding of inter-relations between urban street network and traffic flow can help the planning process of urban systems. Based on cellular automata modeling, this paper studies the influence of aspect ratio of a rectangular urban network on the dynamics of traffic system. The performance of road network is examined with the Macroscopic Fundamental Diagram (MFD). The maximal arrival rate and the critical density of congestion of MFD are investigated as two main indicators for system performance. Under the closed boundary condition, the square network shows the maximum arrival rate, but with a relatively lower critical density of congestion. With the increase of aspect ratio, the arrival rate decreases, while the critical congestion density increases. The phenomena can be explained by the vehicle distribution in the network, the left-turning and U-turning demand, and the average travel distance.

城市交通系统对于人们日常生活的便利和效率很重要。对城市街道网络和交通流之间的相互关系的理解可以帮助城市系统的规划过程。基于元胞自动机建模，研究了矩形城市网络的纵横比对交通系统动力学的影响。使用宏观基本图（MFD）检查路网的性能。研究了MFD的最大到达速率和临界拥塞密度，作为系统性能的两个主要指标。在封闭边界条件下，正方形网络显示最大到达率，但拥塞的临界密度相对较低。随着长宽比的增加，到达率降低，而临界拥塞密度增加。可以通过网络中的车辆分布，左转弯和掉头的需求以及平均行驶距离来解释这种现象。