scholarly journals Effect of U-Turns and Heavy Vehicles on the Saturation Flow Rates of Left-Turn Lanes at Signalized Intersections

2020 ◽  
Vol 12 (11) ◽  
pp. 4485
Author(s):  
Abdelrahman Abuhijleh ◽  
Charitha Dias ◽  
Wael Alhajyaseen ◽  
Deepti Muley
Keyword(s):  
Flow Rate ◽  
Signalized Intersections ◽  
The State ◽  
Heavy Vehicles ◽  
Flow Rates ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Adjustment Factors ◽  
Saturation Flow Rate ◽  
Saturation Flow

The Saturation Flow Rate (SFR) is a primary measure that can be used when estimating intersection capacity. Further, the efficiency of signal control parameters also depends on the accuracy of assumed SFR values. Driver behavior, type of movement, vehicle type, intersection layout, and other factors may have a significant impact on the saturation flow rate. Thus, it is expected that driving environments that have heterogeneous driver populations with different driving habits and cultures may have different SFRs. In practice, the proposed SFRs based on US standards (Highway Capacity Manual, 2016) have been adopted in the State of Qatar without validation or calibration to consider the local road environment and the characteristics of the driving population. This study aims to empirically analyze the saturation flow rates for exclusive left-turn lanes and shared left- and U-turn lanes at two signalized intersections in Doha city, while considering the effects of heavy vehicles and U-turn maneuvers. Empirical observations revealed that the average base SFR, i.e., when the influences from heavy vehicles and U-turns were excluded, could vary approximately from 1800 vehicles per hour per lane (vphpl) to 2100 vphpl for exclusive left-turning lanes and approximately from 1800 vphpl to 1900 vphpl for shared left- and U-turning lanes. Furthermore, this study proposed different adjustment factors for heavy vehicle and U-turn percentages which can be applied in practice in designing signalized intersections, particularly in the State of Qatar.

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

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.

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.

Estimating Intersection Approach Delay Using 1985 and 1994 Highway Capacity Manual Procedures

1996 ◽  
Vol 1555 (1) ◽  
pp. 23-32
Author(s):  
Stephen M. Braun ◽  
John N. Ivan
Keyword(s):  
Field Measurements ◽  
Signalized Intersections ◽  
New Technique ◽  
Adjustment Factor ◽  
Highway Capacity ◽  
Flow Rates ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
A New Technique ◽  
Saturation Flow

The current methods for determining average stopped delay at signalized intersections were studied. Field measurements of average stopped delay were obtained and compared with values computed using both the 1985 and 1994 editions of the Highway Capacity Manual (HCM). The 1994 HCM uses an equation to predict the progression adjustment factor (PF), a new technique for determining the left-turn adjustment factor for saturation flow rates, and a new set of equations for determining the uniform delay parameter for left-turn lane groups with primary and secondary phasing. Overall, the 1994 HCM produces better estimates of intersection stopped delay than the 1985 HCM.

scholarly journals Estimating saturation flow under weak discipline traffic conditions, case study: Iran

2018 ◽  
Vol 46 (2) ◽  
pp. 47-60 ◽  
Author(s):  
Maryam Dehghani-Zadeh ◽  
Mehdi Fallah Tafti
Keyword(s):  
Flow Rate ◽  
Field Data ◽  
Signalized Intersections ◽  
Optimal Timing ◽  
Effective Parameters ◽  
Highway Capacity ◽  
Left Turn ◽  
Saturation Flow Rate ◽  
Saturation Flow

Intersections, as the critical elements and the major bottleneck points of urban street networks, may have inconsistent performances in different countries. This is largely due to the fact that the factors affecting their performance e.g. driving behavior, vehicle characteristics, control methods, and environmental conditions may vary from one country to another. It is, therefore required to take into account these factors when developing or applying available models and methodologies for their capacity analysis or signal control setting. This is particularly important for the countries with heterogeneous and weak discipline traffic streams such as Iran. Meanwhile, estimating the saturation flow rate, which is a key parameter in capacity and delay analysis and in optimal timing of traffic signals, is of great importance. In this study, the possibility of identifying and or developing appropriate models for estimating the saturation flow rate at the signalized intersections in these situations has been explored. For this purpose, a case study performed at the signalized intersections located in the city of Yazd, a medium sized city located in the middle of Iran. Using the data obtained from several intersections together with the application of analytical procedures proposed by American, Australian, Canadian, Indonesian, Iranian and Malaysian highway capacity guides, the saturation flow rate was estimated from both field observations and analytical methods. A comparison of these results indicated that in the protected left-turn situations, the Australian guide produced the best comparable results with the field data. On the other hand, in the permitted left-turn situations, the method proposed in the American Highway Capacity Manual guide produced the best comparable results with the field data. Furthermore, three new models were developed for estimating the saturation flow rate in three different situations namely, unopposed mixed straight and turning traffic movements, opposed mixed straight and turning traffic movements and merely straight through movement. The effective width, traffic composition, and opposite oncoming through traffic flow were considered as the effective parameters in the proposed models. Moreover, using the multivariate regression analysis, the Passenger Car Equivalent coefficients for motorcycles and heavy vehicles were calculated as 0.51 and 2.09, respectively.

Saturation Flow Rate, Start-Up Lost Time, and Capacity for Bicycles at Signalized Intersections

2003 ◽  
Vol 1852 (1) ◽  
pp. 105-113 ◽  
Author(s):  
Winai Raksuntorn ◽  
Sarosh I. Khan
Keyword(s):  
Flow Rate ◽  
Field Studies ◽  
Signalized Intersections ◽  
Highway Capacity Manual ◽  
Start Up ◽  
Lost Time ◽  
Saturation Flow Rate ◽  
Saturation Flow ◽  
Bicycle Lane ◽  
Stop Line

A review of the literature shows that capacity and saturation flow rate for on-street bicycle lanes at intersections have not been measured on the basis of bicycle discharge at intersections at the start of the green phase. The Highway Capacity Manual 2000 recommends a saturation flow rate of 2,000 bicycles per hour for a bicycle lane at a signalized intersection. However, this recommendation is not based on field studies at the intersection and is not a function of the width of the bicycle lane. A revised estimate is provided of saturation flow rate, and an estimate is provided of start-up lost time for bicycles based on data collected at the stop line of signalized intersections. In addition, the lateral stopped distance of automobiles from bicycle lanes, the lateral stopped distance of bicycles from adjacent lanes, and the lateral and longitudinal stopped distance between pairs of bicycles at a signalized intersections are presented. Bicycles may form more than one queue within a bicycle lane at the stop line. Since bicycles maintain a certain distance from the adjacent lane and the curb, the number of queues formed varies based on the width of the bicycle lane. Therefore, the saturation flow rate for a bicycle lane depends on the number of queues or the width of the bicycle lane. The saturation flow rates for bicycle lanes of varying widths are proposed on the basis of the lateral stopped distance of bicycles. Empirical evidence from intersections in Colorado and California is used to propose a new method to estimate the capacity for a bicycle lane.

Effects of U-Turns on Capacities of Signalized Intersections

2005 ◽  
Vol 1920 (1) ◽  
pp. 74-80 ◽  
Author(s):  
Pan Liu ◽  
Jian John Lu ◽  
Jingjing Fan ◽  
Juan C. Pernia ◽  
Gary Sokolow
Keyword(s):  
Regression Model ◽  
Signalized Intersections ◽  
Signalized Intersection ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Bay Area ◽  
Study Team ◽  
Adjustment Factors ◽  
Left Turns ◽  
Saturation Flow

In Florida, the increased use of restrictive medians and directional median openings has generated many U-turns at signalized intersections. There is no widely accepted procedure for estimating the effects of U-turning vehicles on signalized intersection capacity. In the 2000 edition of the Highway Capacity Manual, U-turns are treated as left turns for estimation of saturation flow rates. However, the operational effects of U-turns and left turns are different. This study analyzed the effects of U-turning vehicles on the left-turn saturation flow rate. Data were collected at three signalized intersections in the Tampa Bay area in Florida. In total, the study team recorded the queue discharge times for 260 queues, including 571 U-turning vehicles and 1,441 left-turning vehicles. On the basis of the data collected in the field, a regression model was developed to estimate the relationship between the average queue discharge time for each turning vehicle and the various percentages of U-turning vehicles in the left-turn traffic stream. Adjustment factors for various percentages of U-turning vehicles were also developed by using the regression model. The adjustment factors developed in this study can be directly used to estimate the capacity reduction due to the presence of various percentages of U-turning vehicles at a signalized intersection.

Development of Driver Population Factors for Capacity Analysis of Signalized Intersections

2000 ◽  
Vol 1710 (1) ◽  
pp. 239-245 ◽  
Author(s):  
Yanhu Zhou ◽  
Jian John Lu ◽  
Edward A. Mierzejewski ◽  
Xuewen Le
Keyword(s):  
Flow Rate ◽  
Signalized Intersections ◽  
Capacity Analysis ◽  
Study Results ◽  
Adjustment Factors ◽  
Saturation Flow Rate ◽  
High Level ◽  
Saturation Flow ◽  
The Impact ◽  
Population Adjustment

In the Highway Capacity Manual (HCM), driver population factors are included to adjust for the impact of nonlocal drivers on freeway capacity. There are no such factors in the HCM to account for the possible change of capacity at signalized intersections caused by unfamiliar drivers in the traffic stream. The results obtained from a research study to develop driver population adjustment factors for capacity analysis of signalized intersections are summarized. Detailed procedures for quantifying driver population adjustment factors are presented. The factors were derived on the basis of data collected in Hillsborough, Pinellas, Orange, and Osceola counties in Florida. Study results indicated that nonlocal drivers had a significant impact on the saturation flow rate. When a signalized intersection was identified with a high level of nonlocal drivers, the saturation flow rate as well as the capacity could be reduced by 19 percent, which corresponded to a driver population factor as low as 0.81.

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

2020 ◽  
Vol 12 (2) ◽  
pp. 665 ◽  
Author(s):  
Yi Wang ◽  
Jian Rong ◽  
Chenjing Zhou ◽  
Xin Chang ◽  
Siyang Liu
Keyword(s):  
Traffic Congestion ◽  
National Standard ◽  
Percentage Error ◽  
Heavy Vehicles ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Lane Width ◽  
Adjustment Factors ◽  
Saturation Flow

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.

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.

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