Capacity analysis for roundabout intersections on China national highways

Roundabouts are widely used on national highway system in China. However, no clear guidance or procedures for roundabout capacity analysis have been developed. The unavailability of such a guidance or procedure has practically made it difficult to plan and design roundabouts in China, and potentially it may limit the traffic operations and safety performance in these intersections. A large-scale research was initialed recently to develop capacity analysis procedures for China national highways. Capacity analysis procedure for roundabouts was one of the major tasks in the research. This paper summarizes the research study on the procedure development for roundabout capacity analysis. In the study, thirteen roundabouts from four provinces in China were used for field data collection and analysis. With the data collected from these sites, analytical capacity models based on gap acceptance concept were calibrated and validated. These models include entry capacity, total capacity, and service capacity. Based on these capacity models, adjustment factors were calculated. Thus, a practically useful procedure for roundabout capacity analysis was developed.