Queue-Based Guidance for Signalization Consideration at Two and Three-Legged Intersections

2019 ◽  
Vol 2673 (10) ◽  
pp. 416-426
Author(s):  
Shannon Warchol ◽  
Nagui Rouphail ◽  
Chris Vaughan ◽  
Brendan Kearns
Keyword(s):  
North Carolina ◽  
Traffic Control ◽  
Signalized Intersections ◽  
Data Driven ◽  
Left Turn ◽  
Minor Road ◽  
Adjustment Factors ◽  
Queue Lengths ◽  
Control Devices ◽  
A Minor

This research collected and analyzed gap acceptance in North Carolina to develop a data-driven method for determining the need for considering additional signalization analysis at intersections with fewer than four legs. This method can be used for movements that merge with or cross two lanes of oncoming traffic. It is intended to provide guidance and support to traffic engineers in their decision-making process. Charts are provided to determine the expected 95th percentile queue lengths for left-turn, right-turn, and U-turn movements crossing or merging with two lanes of conflicting traffic. This situation is typically present along four-lane roadways where a one-way primary movement opposes either a minor road right-turn movement or a left-turn movement, or in the case of a median U-turn opening. Adjustment factors to the conflicting flowrate were developed to account for the presence of upstream signalized intersections. This method less frequently recommends further signal consideration when compared with the Manual on Uniform Traffic Control Devices peak hour warrant, but is similar to the delay-based level of service D/E threshold for two-way stop-controlled intersections in HCM6 Chapter 19.

Effect on Vehicle-Pedestrian Conflicts of “Turning Traffic Must Yield to Pedestrians” Sign

1996 ◽  
Vol 1553 (1) ◽  
pp. 38-45 ◽  
Author(s):  
Husham N. Abdulsattar ◽  
Mohammed S. Tarawneh ◽  
Patrick T. McCoy ◽  
Stephen D. Kachman
Keyword(s):  
Traffic Control ◽  
Signalized Intersections ◽  
Legal Obligation ◽  
Left Turn ◽  
Right Of Way ◽  
Two Cities ◽  
Before And After ◽  
Left And Right ◽  
Control Devices ◽  
The Right

Left- and right-turn movements at signalized intersections have been found to be three to six times more hazardous to pedestrians than through movements mainly because drivers fail to observe or yield the right of way to pedestrians. The objective was to evaluate the Turning Traffic Must Yield to Pedestrians sign, which was aimed at reminding turning motorists of their legal obligation to yield the right of way to pedestrians and, consequently, reducing vehicle-pedestrian conflicts. The sign was installed at 12 marked crosswalks in two cities, and vehicle-pedestrian conflict data were collected before and after its installation. The sign was effective in reducing left-turn conflicts 20 to 65 percent and right-turn conflicts 15 to 30 percent; both reductions were statistically significant at the 0.05 level. The sign was significantly more effective in reducing left-turn conflicts than it was for right-turn conflicts. Percentage conflicts between pedestrians and turning traffic decreased as the pedestrian group size increased. In other words, larger pedestrian group sizes encountered fewer conflicts with turning traffic. This result is true for both left- and right-turn movements, regardless of the presence of the sign. Based on the results of this study, it was recommended that the “Turning Traffic Must Yield to Pedestrians” sign be considered for inclusion in the Manual on Uniform Traffic Control Devices.

Operational Impact of Split Intersections

1997 ◽  
Vol 1579 (1) ◽  
pp. 73-78 ◽  
Author(s):  
Abishai Polus ◽  
Ronen Cohen
Keyword(s):  
Minimum Distance ◽  
Signalized Intersections ◽  
Left Turn ◽  
Suburban Areas ◽  
Advantages And Disadvantages ◽  
Minor Road ◽  
Lost Time ◽  
The Right ◽  
The Impact ◽  
Operational Impact

High volumes at urban and suburban intersections may cause considerable delay to vehicles during the peak periods, particularly when the left-turning volume is combined with high through volumes in both directions. The operational impact resulting from converting a major conventional cross intersection into two smaller signalized intersections is analyzed and evaluated. The two intersections are constructed along the minor road, allowing the left-turn movement from the major road to operate simultaneously with the through movement and to be stored in more lanes on the minor road. The general advantages and disadvantages of a split intersection are discussed. It is shown that the split increases capacity because of better efficiency resulting from ( a) the smaller geometry of each intersection, which reduces “lost time,” compared to the geometry of a single larger intersection, ( b) a reduction in the number of signal phases from four to three and an increase in the effective green time for all movements, and ( c) an increase in the number of lanes available for storage of the left-turn movement. It is also shown that delay is reduced, particularly when the flow is close to saturation. The impact of the cycle length and the left-turn volume is evaluated. Further analysis ascertains the minimum distance between the two smaller intersections under two scenarios: ( a) a minimum distance for storage of the left-turn movement and ( b) a longer distance to reduce delays and to allow for the simultaneous start of the green time for the through movements in the two intersections. It is concluded that the longer distance is feasible mainly for new intersections in suburban areas where the right of way is available.

Developing Signal Warrants for Restricted Crossing U-Turn Intersections

2021 ◽  
pp. 036119812110469
Author(s):  
Justice Appiah
Keyword(s):  
Traffic Control ◽  
Simulation Analysis ◽  
Traffic Signals ◽  
Traffic Volume ◽  
Traffic Signal ◽  
Signal Control ◽  
Traffic Signal Control ◽  
Left Turn ◽  
Minor Road ◽  
Intersection Configuration

The restricted crossing U-turn (RCUT) intersection is a form of innovative intersection design that reroutes left-turn and through traffic from the minor road to U-turn crossovers on the major road. When implemented correctly, an RCUT intersection can provide significant safety and operational benefits over the conventional intersection configuration. The RCUT may be controlled by traffic signals, STOP control, merges and diverges, or a combination of these. There is currently no concrete guidance in relation to when the use of traffic signal control is warranted at an RCUT intersection. This study investigated traffic volume conditions that may warrant consideration of traffic signal control at an RCUT intersection. Simulation experiments including two geometric configurations and three traffic control schemes were designed and run in VISSIM to evaluate the effects of traffic conditions on intersection delay and queue lengths. Traffic was varied by changing the composition, approach volumes, and origin–destination flow patterns to reflect different conditions that may occur at the intersection on any given day. For the range of conditions studied, the results of the simulation analysis suggested that the RCUT intersection may operate better with traffic signals (at all junctions) when the minor roadway traffic volume is more than 450 vehicles per hour (vph) and the major roadway has two through lanes. The corresponding minor roadway volume threshold increases to 575 vph when the major roadway has four through lanes.

Teenage Drivers’ Understanding of Traffic Control Devices

2000 ◽  
Vol 1708 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Garry L. Ford ◽  
Dale L. Picha
Keyword(s):  
Traffic Control ◽  
Warning Signs ◽  
Driver Education ◽  
Safe Driving ◽  
Left Turn ◽  
Pavement Markings ◽  
The Road ◽  
Control Devices ◽  
Traffic Control Devices ◽  
Teenage Drivers

Teenage drivers are involved in traffic crashes more often than any other driver group, and their fundamental knowledge of traffic control devices and rules of the road is extremely important in safe driving. Only limited data exist, however, on teenage drivers’ understanding of traffic control devices, and little research has been done on determining their comprehension thereof. Research was performed to document teenage drivers’ ability to understand 53 traffic control devices. These traffic control devices included 6 combinations of sign shape and color; 8 regulatory signs; 14 warning signs; 7 school, highway–railroad grade crossing, and construction warning signs; 7 pavement markings; and 11 traffic signals. Research results were then compared with previous comprehension studies to identify specific traffic control devices that the driving public continually misunderstands. In general, the results indicated that surveyed teenage drivers understood the traffic control devices to some degree. Only nine devices were understood by more than 80 percent of the respondents. The devices found problematic to teenage drivers include combinations of sign shape and color, warning-symbol signs, white pavement markings, flashing intersection beacons, and circular red/green arrow left-turn-signal displays. Recommendations include revising states’ drivers handbooks and increasing emphasis in the driver education curriculum to clarify the meaning and intent of problematic traffic control devices.

scholarly journals Unbalanced Multiple Left Turn Lane Usage Modelling: From Individual Choice to Aggregate Volume

2019 ◽  
Vol 2019 ◽  
pp. 1-13
Author(s):  
Li Li ◽  
Qing-Chang Lu ◽  
Dong Zhang ◽  
Ping Wang ◽  
Gui-Ping Wang
Keyword(s):  
Discrete Choice ◽  
Traffic Control ◽  
Choice Model ◽  
Signalized Intersections ◽  
Influential Factors ◽  
Individual Choice ◽  
Left Turn ◽  
Vehicle Type ◽  
Traffic Distribution ◽  
Turning Radius

Diverse lane preferences of left-turn drivers lead to unbalanced traffic distribution on multiple left-turn lanes. The preferences can be measured in terms of lane usage at macroscopic level and individual lane choice at microscopic level. The data of lane volume and individual lane choices are collected at eight dual or triple left-turn lanes equipped in signalized intersections in China. Linear regression model with dummy variables and discrete choice model were applied to analyse drivers’ lane choosing patterns at macroscopic and microscopic levels, respectively, and results of the two studies are mutually verified and complemented. The drivers’ lane preferences are found to vary with approach configurations, traffic control, and the number of lanes available. Static influential factors, such as turning radius inside the intersection, the design of shadowed lane, and intersection skewedness, as well as dynamic influential factors, including queue length, heavy vehicle in queue back and subject vehicle type, could affect the drivers’ lane preferences. The findings of this study have important implications for intersection design and traffic control in practice.

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.

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.

Crash Modification Factors for the Flashing Yellow Arrow Treatment at Signalized Intersections

2018 ◽  
Vol 2672 (30) ◽  
pp. 142-152 ◽  
Author(s):  
Raghavan Srinivasan ◽  
Bo Lan ◽  
Daniel Carter ◽  
Sarah Smith ◽  
Kari Signor
Keyword(s):  
North Carolina ◽  
Empirical Bayes ◽  
Evaluation Method ◽  
Signalized Intersections ◽  
Left Turn ◽  
Flashing Yellow Arrow ◽  
Crash Modification Factors ◽  
Treatment Category ◽  
Using Data ◽  
Yellow Arrow

This paper presents the results of an evaluation of the flashing yellow arrow (FYA) treatment using data from signalized intersections in Nevada, North Carolina, Oklahoma, and Oregon. The evaluation method was an empirical Bayes before–after analysis. The treatments were divided into seven categories depending on the phasing system in the before period (permissive, protected–permissive, or protected), phasing system in the after period (FYA permissive or FYA protected–permissive), the number of roads where the FYA was implemented (one road or both roads), and the number of legs at the intersections (three or four). The first five treatment categories involved permissive or protected–permissive phasing in the before period. Intersections in these five treatment categories experienced a reduction in the primary target crashes under consideration: left turn crashes and left turn with opposing through crashes. The reduction ranged from 15% to 50%, depending on the treatment category. Intersections that had at least one protected left turn phase in the before period and had FYA protected–permissive left turn phase in the after period experienced an increase in left turn crashes and left turn with opposing through crashes, indicating that replacing a fully protected left turn with FYA will likely cause an increase in left turn crashes.

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