Redundancy Analysis And Optimization Design Of Urban Road Network Under The Influence Of Rainfall

China’s urban renewal and development has entered an important period.However,with the continuous growth of vehicle ownership,traffic problems such as congestion have become more and more serious,and weather conditions such as rainfall have brought great challenges to the daily operation of road traffic.The concept of’resilient city’ provides a new idea to solve this problem.Redundancy,as one of the important attributes of resilience,can improve the reliability of urban road network traffic operation.Different grades and types of road section units make the traffic operation under daily rainfall present diversified characteristics,which is closely related to redundancy.Under this background,this thesis studies the redundancy analysis and optimization design of urban road network under the influence of rainfall.Firstly,the influence on the traffic of different grades and types of road section units under different intensity rainfall is analyzed,and case studies are carried out based on GPS track data of a city in Guangdong Province.The results show that the speed reduction coefficient of underpass tunnel increases with the increase of rainfall intensity,while the speed reduction coefficient of elevated section has no obvious change trend.From the perspective of road grades,the speed reduction coefficients of all grades of non-bridge and tunnel roads increase obviously with the increase of rainfall intensity,among which non-bridge and tunnel expressways and non-bridge and tunnel trunk roads are obviously affected.On this basis,the failure probability and calculation formula of road section units are studied,and the normal distribution parameters of speed reduction coefficient of each road section units are determined.Secondly,based on the reasonable routes,the redundancy calculation model of urban road network facing the influence of rainfall is established.The variation of urban traffic demand and the applicable traffic allocation method under rainfall scenario are analyzed,and a redundancy optimization design model of urban road network considering travel efficiency and construction cost is constructed,which is solved by genetic algorithm.Then,combined with the urban trunk road network with different structure layout,numerical examples are analyzed.The calculation results show that:the checkerboard road network itself has a high redundancy,and the gain of improving its redundancy by setting the expressway is much less than the increase of construction cost.For small and medium-sized cities,the belt trunk road network can improve redundancy by setting expressways.The proposed model has a certain rationality and construction significance.Finally,a case study is carried out based on a regional trunk road network in Zhengzhou.The redundancy of the current trunk road network in the study area is 2.74,and the redundancy is increased to 3.34 after optimized by the constructed mathematical model,that is,when the construction cost is only increased by 10.2%,the redundancy is increased by 21.9%and the total travel time cost is reduced by 8.25%.Then,the influence of road design speed and design capacity on the redundancy of trunk road network in the study area is analyzed.The results show that compared with road design speed,the effect of road design capacity on road network redundancy is significant.