Estimation Method of Saturation Flow Rate for Shared Left-Turn Lane at the Signalized Intersection, Part I: Methodology

2019 ◽  
pp. 39-47
Author(s):  
Ruru Tang ◽  
Yunhao Wang ◽  
Yiming Bie ◽  
Zhiqiang Fang
Keyword(s):  
Flow Rate ◽  
Estimation Method ◽  
Signalized Intersection ◽  
Left Turn ◽  
Saturation Flow Rate ◽  
Saturation Flow

Impact of Turning Lane Storage Length and Turning Proportions on Throughput at Oversaturated Signalized Intersections

2021 ◽  
pp. 036119812110171
Author(s):  
A. M. Tahsin Emtenan ◽  
Christopher M. Day
Keyword(s):  
Flow Rate ◽  
Cycle Length ◽  
Signal Timing ◽  
Real World Data ◽  
Left Turn ◽  
Common Response ◽  
Cycle Lengths ◽  
Saturation Flow Rate ◽  
Saturation Flow ◽  
Timing Strategies

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.

Hybrid Model for Estimating Permitted Left-Turn Saturation Flow Rate

1996 ◽  
Vol 1566 (1) ◽  
pp. 54-63 ◽  
Author(s):  
Gang-Len Chang ◽  
Chien-Yu Chen ◽  
Cesar Perez
Keyword(s):  
Hybrid Model ◽  
Flow Rate ◽  
Heavy Vehicle ◽  
Simulation Experiments ◽  
Left Turn ◽  
Explanatory Variables ◽  
Complex Interactions ◽  
Saturation Flow Rate ◽  
Log Linear ◽  
Saturation Flow

This study explored the integration of analytical formulations with simulation results for estimating the complex permitted saturation flow rate. The proposed hybrid model captured most tractable interactions between the permitted flow rate and the opposing flows with the widely used formulation by Drew, which serves as one of the primary explanatory variables. To further consider the complex interactions between the permitted flow rate and all other associated factors, which often are not consistent with the assumptions used in analytical derivations, this study modeled the intractable relations as multiplicative adjustment terms and estimated their parameters with log-linear regression. Such a hybrid formulation offers the flexibility to incorporate various additional critical factors on the permitted flow rate, including the variation of driving behavior, the number of opposing lanes, the progression quality, and the heavy vehicle percentage. The preliminary tests with extensive simulation experiments have shown very promising results.

scholarly journals Traffic Characteristics of Protected/Permitted Left-Turn Signal Displays

2000 ◽  
Vol 1708 (1) ◽  
pp. 28-39 ◽  
Author(s):  
David A. Noyce ◽  
Daniel B. Fambro ◽  
Kent C. Kacir
Keyword(s):  
Response Time ◽  
Flow Rate ◽  
Left Turn ◽  
Start Up ◽  
Green Ball ◽  
Lost Time ◽  
Saturation Flow Rate ◽  
Driver Understanding ◽  
Saturation Flow

At least four variations of the permitted indication in protected/permitted left-turn (PPLT) control have been developed in an attempt to improve the level of driver understanding and safety. These variations replace the green ball permitted indication with a flashing red ball, a flashing yellow ball, a flashing red arrow, or a flashing yellow arrow indication. In addition, the Manual on Uniform Traffic Control Devices allows several PPLT signal display arrangements. The variability in indication and arrangement has led to a myriad of PPLT displays throughout the United States. The level of driver understanding related to each PPLT display type, and the associated impact on traffic operations and safety, has not been quantified. A study was conducted to evaluate the operational characteristics associated with different PPLT signal displays. Specifically, the study quantified saturation flow rate, start-up lost time, response time, and follow-up headway associated with selected PPLT displays. No differences in saturation flow rate and start-up lost time were found due to the type of PPLT signal display. Saturation flow rates ranged from 1,770 to 2,400 vehicles per hour of green per lane and were related to differences in driver behavior between geographic locations. The variation in start-up lost time and response time between locations was primarily related to differences in phase sequence. The flashing red permitted indications were associated with the longest follow-up headway times, since drivers are required to stop before turning left with a flashing red permitted indication. The shortest follow-up headway was associated with the five-section cluster display using a green ball indication.

scholarly journals Impact of Guideline Markings on Saturation Flow Rate at Signalized Intersections

2019 ◽  
Vol 2019 ◽  
pp. 1-13 ◽  
Author(s):  
Zhengtao Qin ◽  
Jing Zhao ◽  
Shidong Liang ◽  
Jiao Yao
Keyword(s):  
Flow Rate ◽  
Signalized Intersections ◽  
Estimation Model ◽  
Left Turn ◽  
Proposed Model ◽  
Research Goal ◽  
Saturation Flow Rate ◽  
Saturation Flow ◽  
The Impact

Many intersections around the world are irregular crossings where the approach and exit lanes are offset or the two roads cross at oblique angles. These irregular intersections often confuse drivers and greatly affect operational efficiency. Although guideline markings are recommended in many design manuals and codes on traffic signs and markings to address these problems, the effectiveness and application conditions are ambiguous. The research goal was to analyze the impact of guideline markings on the saturation flow rate at signalized intersections. An adjustment estimation model was established based on field data collected at 33 intersections in Shanghai, China. The proposed model was validated using a before–after case study. The underlying reasons for the impact of intersection guideline markings on the saturation flow rate are discussed. The results reveal that the improvement in the saturation flow rate obtained from painting guide line markings is positively correlated with the number of traffic lanes, offset of through movement, and turning angle of left-turns. On average, improvements of 7.0% and 10.3% can be obtained for through and left-turn movements, respectively.

scholarly journals Automatic Estimation Method for Intersection Saturation Flow Rate Based on Video Detector Data

2018 ◽  
Vol 2018 ◽  
pp. 1-9 ◽  
Author(s):  
Linhong Wang ◽  
Yunhao Wang ◽  
Yiming Bie
Keyword(s):  
Time Series ◽  
Flow Rate ◽  
Field Measurement ◽  
Measurement Method ◽  
Estimation Method ◽  
Ordinary Least Squares ◽  
Automatic Estimation ◽  
Saturation Flow Rate ◽  
Saturation Flow ◽  
Video Detector

Saturation flow rate (SFR) is a fundamental parameter to the level of service evaluation, lane capacity calculation, and signal timing plan optimization at signalized intersections. It is affected by a variety of factors including weather conditions, lane width, and the type of the driver. How to accurately estimate the SFR remains one of the most important tasks in traffic engineering. Existing studies generally rely on the field measurement method which requires a large number of people collecting data at the intersection. As a result, the method incurs a high economic cost and cannot adapt to the dynamic change of SFR. In recent years, video detectors have been widely installed at intersections which are capable of recording the time each vehicle passes the stop line, the number plate of each vehicle, and the vehicle type. This paper therefore aims to propose an automatic estimation method for the SFR based on video detector data in order to overcome the limitation of the field measurement method. A prerequisite for estimating the SFR is to recognize the saturation headway. We consider the actual vehicle headway as time series and build an auxiliary regression equation whose parameters are estimated through the ordinary least squares method. We employ the Dickey-Fuller test to verify whether the headways in the time series are saturation headways. An iterative method using quantiles is proposed to filter out abnormal data. The SFR is finally calculated using the average value of saturation headways. To demonstrate the proposed method, we conduct a case study using data from an intersection with three entrance lanes in Qujing city, Yunnan Province, China. The overall estimation process is displayed and the impacts of quantile selection and data duration on the estimation accuracy are analyzed.

Relationship of Lane Width to Saturation Flow Rate on Urban and Suburban Signalized Intersection Approaches

2007 ◽  
Vol 2027 (1) ◽  
pp. 45-51 ◽  
Author(s):  
Ingrid B. Potts ◽  
John F. Ringert ◽  
Karin M. Bauer ◽  
John D. Zegeer ◽  
Douglas W. Harwood ◽  
...  
Keyword(s):  
Flow Rate ◽  
Signalized Intersection ◽  
Lane Width ◽  
Saturation Flow Rate ◽  
Saturation Flow ◽  
Relationship Of
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