Modelling the saturation flow rate for continuous flow intersections based on field collected data.

Xing Gao,Jing Zhao,Meng Wang,Feng Chen

doi:10.1371/journal.pone.0236922

Abstract

The continuous flow intersection [CFI) is an unconventional intersection design which has been used in many cities all over the world. However, as an important parameter for the geometric design, signal timing, and operation evaluation, the saturation flow rate at CFI has not been carefully examined. In this paper, a saturation flow rate adjustment model for CFI intersections is established based on field data under the calculation framework of the HCM2016. Four movements related with CFI, namely the left-turn at the CFI approach, through movement at the CFI approach, left-turn at the pre-signal, and exit movement at the pre-signal, are discussed. The proposed model is validated and the relative error is less than 10%. The treatments to mitigate the negative impact on the saturation flow rate at the CFI are also recommended. The results show the saturation flow rate of the first three movements are decreased due to the CFI control. For the left-turn, through movement, and left-turn at the pre-signal, the degree of the reduction of the saturation flow rate are mainly related to the heavy vehicle ratio, the proportion of lane changing vehicles, and the length of displaced left-turn lanes, respectively.

Highlights

The saturation flow rate is the maximum capacity of continuous traffic flow at intersections during the green time in an hour, which is a vital parameter to calculate vehicle delay and queue length at signalized intersections and a basic parameter to determine the green ratio
In order to deal with the deficiency, the objective of this study is to develop a saturation flow rate adjustment model for continuous flow intersection (CFI) intersections based on field collected data under the calculation framework of the HCM2016 [1]
For the through movement at the CFI approach, since the lane choice and lane changes caused by lane dislocation is the main reason why the through saturation flow rate of the CFI is less than that of the conventional intersection, the striking coloured guide line can be used and some physical facilities can be added between lanes at the intersection such as yellow flashing lights to streamline the traffic flow and reduce the proportion of lane changing

Summary

Introduction

The saturation flow rate is the maximum capacity of continuous traffic flow at intersections during the green time in an hour, which is a vital parameter to calculate vehicle delay and queue length at signalized intersections and a basic parameter to determine the green ratio. Many works have been done to establish the adjustment factors of signalized intersection capacity. For some influencing factors with common cognition, such as the lane width, heavy vehicles, grade, parking, bus blockage, area type, lane utilization, right turns, left turns, and pedestrians and bicycles, have been subordinated to the widely used highway capacity manuals, such as HCM2016 [1]. Other adjustment factors, such as short-lane [2, 3], driving behaviour [4], red light camera [5], green.

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Discussion

Conclusion