The Capacity Estimation of Unsignalized Roundabout and Traffic Circle under Mixed Traffic Flow
Date Issued
2014
Date
2014
Author(s)
Wan, Chia-Hao
Abstract
Recently, many countries in Europe and the United States promote modern roundabout and emphasize that this intersection type is safer and more efficient than traditional traffic circle or 4-ways stop. In Taiwan, scooters cover a large proportion of the traffic flows. The feasibility of traffic circle or modern roundabout in mixed traffic flow in Taiwan is the topic in this research. Therefore, this research focuses on the capacity of unsignalized roundabout and traffic circle for the mixed traffic flow.
Based on previous studies of the gap acceptance theorem of modern roundabout and a survey of the driving behaviors at unsignalized traffic circles in Taiwan, this research developed a set of estimation formulas which can be used in both modern roundabout and traditional traffic circle for mixed traffic flow. Many objective variables were considered, including the number of lanes, the scooter rate, the radius and the turning rate. Driver behavior parameters contained the saturated headway, the follow up time and the critical lag.
This research accomplished driver behavior parameters in order to estimate the mixed traffic flow in Taiwan. The capacity formulas were verified through the traffic simulation software, VISSIM. And the MAPE values were under 10%. It showed that the capacity formulas could be used for the mixed traffic flow with accuracy.
This research also provided a method to obtain the scooter’s PCE value on roundabout. Through the PCE value, the average delay of each vehicle unit could be calculated, and the level of service can be analyzed.
Additionally, this research simulated the capacities of different types of intersections, such as that of unsignalized roundabout, signalized roundabout, 4-ways stop and signalized crossroads. The result showed that the efficiency of modern roundabout could be better than other types of intersection under some situations. In most situations, signalized modern roundabout can have a higher efficiency than other types of intersections. According to simulated results, a decision flowchart could be generated and provided to planners and researchers in the future.
Subjects
傳統圓環
現代圓環
容量
混合車流
混合比
接受間距
無號誌化路口
Type
thesis
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