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.

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.

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

2015 ◽  
Vol 2015 ◽  
pp. 1-7 ◽  
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.

Phase Capacity Characteristics for Signalized Interchange and Intersection Approaches

1998 ◽  
Vol 1646 (1) ◽  
pp. 96-105 ◽  
Author(s):  
James A. Bonneson ◽  
Carroll J. Messer
Keyword(s):  
Flow Rate ◽  
Urban Areas ◽  
High Volume ◽  
Traffic Volume ◽  
Passenger Car ◽  
Start Up ◽  
Lost Time ◽  
Saturation Flow Rate ◽  
Saturation Flow

Described in this paper are the development, calibration, and application of models that collectively can be used to predict the saturation flow rate and start-up lost time of through movements at signalized interchange ramp terminals and other closely spaced intersections. These models were calibrated with data collected at 12 interchanges. It is concluded that saturation flow rate decreases as the distance to the downstream queue decreases. This queue is formed by the signal at a downstream intersection. Saturation flow rate increases with traffic pressure, as quantified by traffic volume per cycle per lane. It is recommended that an ideal saturation flow rate of 2,000 passenger-car units per hour of green per lane be used for signalized ramp terminals and other high-volume intersections in urban areas. The data collected for this research indicate that start-up lost time increases with saturation flow rate.

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 Effect on the Left-Turn Saturation Flow Rate Caused by Turning-Radius and Turning-Angle at Signalized Intersections

2002 ◽  
Vol 19 ◽  
pp. 739-744 ◽  
Author(s):  
Yoshiyuki KAWAI ◽  
Shigenori SHIKATA ◽  
Masahiko KATAKURA ◽  
Takashi OGUCHI
Keyword(s):  
Flow Rate ◽  
Signalized Intersections ◽  
Turning Angle ◽  
Left Turn ◽  
Saturation Flow Rate ◽  
Turning Radius ◽  
Saturation Flow

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 Start-up Lost Time and its Effect on Signalized Intersections in Turkey

2017 ◽  
Vol 29 (3) ◽  
pp. 321-329 ◽  
Author(s):  
S. Pelin Çalışkanelli ◽  
Figen Coşkun Atasever ◽  
Serhan Tanyel
Keyword(s):  
Response Time ◽  
Cycle Time ◽  
Signalized Intersections ◽  
Start Up ◽  
Lost Time ◽  
Saturation Flow ◽  
The Relationship

Start-up lost time is an important parameter in performance of signalized intersections which may in turn depict the effect of behaviour of different drivers for different countries. In this study the parameters affecting the startup lost time in Turkey will be defined and a model will be established to present the relationship between start-up lost time, saturation flow as well as start response time with the behaviour of Turkish drivers. For this purpose, observations were carried out at eight intersections in Turkey. Analyses have shown that saturation headways decrease with the increase in time in start response since the drivers in the 2nd and higher rows of a queue have a longer time to get prepared to discharge. Results also indicated that start-up lost time increases rapidly as cycle time increases, and lower start-up lost time values can be observed in left or right turning lanes.

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