Intersection signal timing optimization method based on dynamic saturation flow rate

During oversaturated conditions, common objectives of signal timing are to maximize vehicle throughput and manage queues. A common response to increases in vehicle volumes is to increase the cycle length. Because the clearance intervals are displayed less frequently with longer cycle lengths and fewer cycles, more of the total time is used for green indications, which implies that the signal timing is more efficient. However, previous studies have shown that throughput reaches a peak at a moderate cycle length and extending the cycle length beyond this actually decreases the total throughput. Part of the reason for this is that spillback caused by the turning traffic may cause starvation of the through lanes resulting in a reduction of the saturation flow rate within each lane. Gaps created by the turning traffic after a lane change may also reduce the saturation flow rate. There is a relationship between the proportions of turning traffic, the storage length of turning lanes, and the total throughput that can be achieved on an approach for a given cycle length and green time. This study seeks to explore this relationship to yield better signal timing strategies for oversaturated operations. A microsimulation model of an oversaturated left-turn movement with varying storage lengths and turning proportions is used to determine these relationships and establish a mathematical model of throughput as a function of the duration of green, storage length, and turning proportion. The model outcomes are compared against real-world data.

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Mixed Traffic Flow Signal Timing Optimization Method Considering E-Bike Expansion Influence

Journal of Transportation Engineering Part A Systems ◽

10.1061/jtepbs.0000478 ◽

2021 ◽

Vol 147 (2) ◽

pp. 04020155

Author(s):

Yuhong Gao ◽

Zhaowei Qu ◽

Jingling Jiang ◽

Xianmin Song ◽

Yingji Xia

Keyword(s):

Traffic Flow ◽

Optimization Method ◽

Signal Timing ◽

Mixed Traffic ◽

Timing Optimization ◽

Mixed Traffic Flow ◽

Flow Signal ◽

Signal Timing Optimization

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Estimation of Saturation Flow Rate and Start-Up Lost Time for Signal Timing Based on Headway Distribution

Discrete Dynamics in Nature and Society ◽

10.1155/2015/304823 ◽

2015 ◽

Vol 2015 ◽

pp. 1-7 ◽

Cited By ~ 2

Author(s):

Yi Zhao ◽

Wenbo Zhang ◽

Jian Lu ◽

Wenjun Zhang ◽

Yongfeng Ma

Keyword(s):

Flow Rate ◽

Queue Length ◽

Signal Timing ◽

Start Up ◽

Adjustment Factors ◽

Headway Distribution ◽

Lost Time ◽

Saturation Flow Rate ◽

New Perspective ◽

Saturation Flow

This study aimed to calibrate saturation flow rate (SFR) and start-up lost time (SLT) when developing signal timing. In current commonly used methods, SFR for one given lane is usually calibrated from many subjective adjustment factors and a fixed result. SLT is calculated based on the fixed SFR, which prevents local applications in China. Considering the importance of traffic behavior (headway) in determining SFR and SLT, this study started from headway distribution and attempted to specify the relationships between headway and vehicle position directly. A common intersection in Nanjing, China, was selected to implement field study and data from 920 queues was collected. Headway distribution was explored and the 78th percentile of headway at each position was selected to build model. Based on the developed relationships, SFR and SLT were calibrated. The results showed that SFR and SLT were correlated with queue length. Moreover, the results showed that it was difficult to reach saturated state even with a long queue length. This paper provides a new perspective on calibrating important parameters in signal timing, which will be useful for traffic agencies to complete signal timing by making the process simpler.

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Investigation of saturation flow rate using video camera at signalized intersections in Jordan

Open Engineering ◽

10.1515/eng-2021-0021 ◽

2020 ◽

Vol 11 (1) ◽

pp. 216-226

Author(s):

Bara’ W. Al-Mistarehi ◽

Ahmad H. Alomari ◽

Mohamad S. Al Zoubi

Keyword(s):

Flow Rate ◽

Standard Procedure ◽

Video Camera ◽

Signalized Intersections ◽

Speed Limit ◽

Local Conditions ◽

Highway Capacity Manual ◽

Saturation Flow Rate ◽

Turning Radius ◽

Saturation Flow

AbstractThis study aimed to investigate a potential list of variables that may have an impact on the saturation flow rate (SFR) associated with different turning movements at signalized intersections in Jordan. Direct visits to locations were conducted, and a video camera was used. Highway capacity manual standard procedure was followed to collect the necessary traffic data. Multiple linear regression was performed to classify the factors that impact the SFR and to find the optimal model to foretell the SFR. Results showed that turning radius, presence of camera enforcement, and the speed limit are the significant factors that influence SFR for shared left- and U-turning movements (LUTM) with R2 = 76.9%. Furthermore, the presence of camera enforcement, number of lanes, speed limit, city, traffic volume, and area type are the factors that impact SFR for through movements only (THMO) with R2 = 69.6%. Also, it was found that the SFR for LUTM is 1611 vehicles per hour per lane (VPHPL),which is less than the SFR for THMO that equals to 1840 VPHPL. Calibration and validation of SFR based on local conditions can improve the efficiency of infrastructure operation and planning activities because vehicles’ characteristics and drivers’ behavior change over time.

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