Abstract: At present, the road network structure of most cities in China has certain drawbacks: the traffic volume of both main and branch roads in some road networks is unevenly distributed, resulting in congestion of main roads and surplus traffic capacity of branch roads. In addition, some cities attach importance to main roads and neglect branch ones, making it impossible to effectively connect high-level roads to low-grade ones within the city. In order to avoid the similar problems in the process of future urban development, it is necessary to introduce the microcirculation theory in urban future planning, which can make a reasonable combination of roads of various grades and improve road utilization. It can also divert traffic on arterial roads, relieve traffic pressure, and increase the driving speed of vehicles in the city.
In order to study the microcirculation organization optimization of urban internal road network, a two-tier planning model based on key edge combination optimization is introduced. Firstly, Python is used to crawl the traffic flow data of a certain area in Zhengzhou from October 2020 to November 2021, including traffic volume and running speed, and the collected data is used to perform a single-sample Kolmogorov-Smirnov test by the SPSS software to redefine the service level of the road network. Secondly, the maximum increase key edge is used to expand the capacity of the city’s internal branch road, the traffic volume of the congested section of the main road is diverted in the expanded secondary branch, the SMHD mobile grid method is used to determine the specific location of the road section to be opened, and the optimal combination of the key edge of the branch expansion key side with the road section to be opened is obtained by simulating the vehicles in the road network by VISSIM. Finally, based on the optimal combination of key edges, the upper planning model with the best average vehicle running speed and road network smoothness and the lower planning model with balanced distribution of traffic flow are constructed, so as to further optimize the road network. After the analysis of the examples, it is found that: (1)compared with the original road network structure, the road network structure optimized again after identifying the key sections of the road network can increase the average running speed of the main road and branch road vehicles by 20.43% and 11.29%, respectively; (2)the original E-level service level of main and branch roads is upgraded to D-level, and the original D-level service level of the main and branch roads is upgraded to C-level; (3)after optimization, the smoothness of roads at all levels has been greatly improved, and vehicle operation has become smoother.
Based on the key sections of the road network, a double-layer planning model of the microcirculation road network structure in the city is constructed, which effectively alleviates the traffic pressure of the main road and the congestion waiting time of vehicles, improves the smoothness and safety of vehicle driving to a certain extent, and has certain feasibility in the microcirculation of the actual urban road network. However, it is still necessary to refine the “capillaries” in the city, such as considering the control of branch road traffic signals in different areas and adjusting some road sections to “ban left or right”, which is the focus of future road network research.

Key words: traffic congestion, urban road network microcirculation, road service level, road gateway construction edge identification, two-level planning model

摘要： 为研究城市内部路网的微循环组织优化,介绍一种基于关键边组合优化的双层规划模型。首先,利用已知数据重新定义路网服务水平;其次,引入最大增流关键边对路网内部支路进行扩容的同时用SMHD移动网格法确定待打通路段具体位置,利用VISSIM对路网中车辆进行仿真后得到支路扩容关键边和待打通路段最优组合;最后基于关键边的最优组合构建路网中以车辆平均运行速度、路网畅通性最优的上层规划模型和交通流均衡分配的下层规划模型,将路网进一步优化。经算例分析得:(1)与原有路网相比,对路网关键路段识别后再次优化的路网结构可使主路及支路车辆的平均运行速度分别提升20.43%和11.29%;(2)主路及支路原有E级服务水平提升到D级,主路及支路原有D级服务水平提升到C级;(3)优化后各级道路的畅通性得到大幅提升,车辆运行更加通畅。

关键词: 交通拥堵, 城市路网微循环, 道路服务水平, 路网关建边识别, 双层规划模型