左进地下快速路合流区交通流特征研究

A Study on the Features of Traffic Flow at Left-side Merging Areas of Urban Freeways

分析左进快速路合流区交通流特征,对于城市交通有效管理有着重要的意义。在实测数据基础上,对比了左进与右进快速路合流区的交通流基本图,分析了两者在通行能力、临界占有率、自由流车速等方面的差异。采用车速标准差作为指标分析两者的车速离散性,对比了车道利用情况。结果表明,左进快速路合流区的通行能力、临界占有率分别为5 250veh/h,0.18,明显低于右进快速路合流区的值6 210veh/h,0.27;在不同占有率下,左进快速路合流区车速离散程度高于右进快速路合流区,当占有率达到0.18时,车速标准差值增大至11.47,即行车安全性显著降低;在车道利用情况上,左进快速路合流区中间车道利用率的增加,使匝道车流汇入难度加大。对左进快速路合流区的交通管控应与右进快速路合流区有所区分,合理设置交通控制参数,加强安全管理,提高行车安全。

Analysis of the features of traffic stream flow characteristics at left-side merging areas on of urban freeways is important for an effective urban traffic management.Based on the data collected from urban freeways in Shanghai,this paper compares the fundamental diagram of traffic flows at left-side and right-side merging areas,and analyzes their differences in terms of capacity,critical occupancy,and free flow speed.Standard deviation of speed is used to describe the degree of speed dispersion.The volume distributions of different lanes at the two areas are also compared.The results show that the capacity and the critical occupancy rate of the left-merging areas are 5 250veh/h and 0.18 respectively.The capacity and the critical occupancy rate of the right-side merging areas are 6 210veh/h and 0.27 respectively,which are much larger.The speed dispersion of the left-side merging areas under different occupancies is higher than that of the right-side merging area.When the occupancy of the left-side merging areas reaches 0.18,the standard deviation of speed increases to 11.47,which means the safety is significantly compromised.The increase of traffic at middle lanes will increase the difficulty for merging.Therefore,different control measures for left-side and right-side merging areas should be implemented.Based on the results from this study,appropriate control measures can be set up to improve safety at the left-merging areas.