Traffic Flow Characteristics of Ramp Merging Bottleneck on Urban Expressway

With the construction of expressways in cities, the ramp merging bottlenecks have attracted much attention, which restrict the capacity of expressways and affect traffic safety. In this paper, traffic data of upstream section, merging section, and downstream section of the bottleneck in Yingtian Avenue in Nanjing, China are collected and analyzed as an example. The bottleneck characteristics are studied from the perspectives of both macroscopic traffic flow and microscopic vehicle behaviors. The traffic factors affecting the bottleneck are investigated as well. Based on measured traffic data from video observation, characteristics of mainstream flow and merging flow are analyzed on a macroscopic and microscopic level. The relationship between traffic parameters is analyzed to study characteristics of the bottleneck, and three equations are worked out to describe the relevance.