An Analysis of the Interactions between Adjustment Factors of Saturation Flow Rates at Signalized Intersections

Yi Wang,Xin Chang,Jian Rong,Siyang Liu,Chenjing Zhou

doi:10.3390/su12020665

Abstract

An insufficient functional relationship between adjustment factors and saturation flow rate (SFR) in the U.S. Highway Capacity Manual (HCM) method increases an additional prediction bias. The error of SFR predictions can reach 8–10%. To solve this problem, this paper proposes a comprehensive adjusted method that considers the effects of interactions between factors. Based on the data from 35 through lanes in Beijing and 25 shared through and left-turn lanes in Washington, DC, the interactions between lane width and percentage of heavy vehicles and proportion of left-turning vehicles were analyzed. Two comprehensive adjustment factor models were established and tested. The mean absolute percentage error (MAPE) of model 1 (considering the interaction between lane width and percentage of heavy vehicles) was 4.89% smaller than the MAPE of Chinese National Standard method (Standard Number is GB50647) at 13.64%. The MAPE of model 2 (considering the interaction between lane width and proportion of left-turning vehicles was 33.16% smaller than the MAPE of HCM method at 14.56%. This method could improve the accuracy of SFR prediction, provide support for traffic operation measures, alleviate the traffic congestion, and improve sustainable development of cities.

Highlights

With the rapid development of economy and society, the number of vehicles has been increasing rapidly in developing countries such as China [1]
Previous studies have shown that the capacity of intersections is less than 50% of the road sections, and the delay accounts for 80% of the road network
The narrower lane widths demonstrated saturation flow rates from 2% to 5% lower than those in the baseline surveys, whereas the wider lane widths demonstrated saturation flow rates 5% higher

Summary

Introduction

With the rapid development of economy and society, the number of vehicles has been increasing rapidly in developing countries such as China [1]. In 2018, the average daily congestion duration was nearly three hours in Beijing [2]. This trend has been spreading from large cities to small and medium-sized cities. Previous studies have shown that the capacity of intersections is less than 50% of the road sections, and the delay accounts for 80% of the road network. Acceleration, and deceleration, the fuel consumption and emission of vehicles will inevitably increase at signalized intersections. It is becoming an important but difficult point how to improve the traffic capacity and alleviate the traffic congestion [5]

Objectives

Methods

Results

Conclusion