Evaluating the Impacts of Unconventional outside Left-Turn Lane Design on Traffic Operations at Signalized Intersections

2011 ◽  
Vol 2257 (1) ◽  
pp. 62-70 ◽  
Author(s):  
Pan Liu ◽  
Jingjing Wan ◽  
Wei Wang ◽  
Zhibin Li
Keyword(s):  
Signalized Intersections ◽  
Traffic Operations ◽  
Left Turn

A Capacity Estimation Model for a Contraflow Left-Turn Pocket Lane at Signalized Intersections

2018 ◽  
Vol 2672 (17) ◽  
pp. 22-34 ◽  
Author(s):  
Yi Zhao ◽  
Rachel M. James ◽  
Lin Xiao ◽  
Joe Bared
Keyword(s):  
Signalized Intersections ◽  
Signalized Intersection ◽  
Traffic Operations ◽  
Estimation Model ◽  
Capacity Estimation ◽  
Average Delay ◽  
Left Turn ◽  
Traffic Demand ◽  
Key Characteristics ◽  
The Impact

Alternative intersection designs are increasingly proposed and adopted by different agencies to meet the needs of growing traffic demand and constrained transportation resources. The left turn (LT) is one of the most critical movements at signalized intersections from both a safety and operations perspective. Heavy LT volumes are especially impactful to the operational efficiency of a signalized intersection and often result in queue spillback. A contraflow left-turn pocket lane (CLPL) is proposed to mitigate congestion caused by heavy LT demand and has been shown in simulation to greatly mitigate the impact of queue spillback. The CLPL dynamically uses the opposing through lane (OTL) as an additional LT lane within the signal cycle on a temporary basis when the OTL is not occupied by through traffic. While geometric design schematics and analytical procedures for estimating delay have been proposed and discussed in existing literature, methodologies for estimating capacity benefits and traffic operations are not yet well defined. This paper has three primary contributions to the literature: development of a probabilistic capacity estimation model, exploration of the impact of key characteristics (e.g., cycle length, LT demand, lane selection preference) on estimated intersection capacity, and recommendations for the real-world implementation of a CLPL. The simulation results indicate that the CLPL treatment can increase a signalized intersection’s throughput up to 25% and decrease the intersection’s average delay by 35%.

Modeling Capacity of Through Movement at Signalized Intersection Affected by Short Left-Turn Bay under Different Signal Settings

2021 ◽  
pp. 036119812110064
Author(s):  
Zihang Wei ◽  
Yunlong Zhang ◽  
Xiaoyu Guo ◽  
Xin Zhang
Keyword(s):  
Cycle Length ◽  
Signalized Intersections ◽  
Signalized Intersection ◽  
Essential Factor ◽  
Highway Capacity ◽  
Left Turn ◽  
Highway Capacity Manual ◽  
Proposed Model ◽  
Vehicle Demand ◽  
The One

Through movement capacity is an essential factor used to reflect intersection performance, especially for signalized intersections, where a large proportion of vehicle demand is making through movements. Generally, left-turn spillback is considered a key contributor to affect through movement capacity, and blockage to the left-turn bay is known to decrease left-turn capacity. Previous studies have focused primarily on estimating the through movement capacity under a lagging protected only left-turn (lagging POLT) signal setting, as a left-turn spillback is more likely to happen under such a condition. However, previous studies contained assumptions (e.g., omit spillback), or were dedicated to one specific signal setting. Therefore, in this study, through movement capacity models based on probabilistic modeling of spillback and blockage scenarios are established under four different signal settings (i.e., leading protected only left-turn [leading POLT], lagging left-turn, protected plus permitted left-turn, and permitted plus protected left-turn). Through microscopic simulations, the proposed models are validated, and compared with existing capacity models and the one in the Highway Capacity Manual (HCM). The results of the comparisons demonstrate that the proposed models achieved significant advantages over all the other models and obtained high accuracies in all signal settings. Each proposed model for a given signal setting maintains consistent accuracy across various left-turn bay lengths. The proposed models of this study have the potential to serve as useful tools, for practicing transportation engineers, when determining the appropriate length of a left-turn bay with the consideration of spillback and blockage, and the adequate cycle length with a given bay length.

Derivation of Decision Boundaries for Left-Turn Treatments at Signalized Intersections

2017 ◽  
Vol 2620 (1) ◽  
pp. 1-9 ◽  
Author(s):  
Andrew Raessler ◽  
Jidong J. Yang
Keyword(s):  
Decision Making ◽  
Signalized Intersections ◽  
Maintenance Costs ◽  
Left Turn ◽  
Practical Guidelines ◽  
Decision Boundaries ◽  
Boundary Curves ◽  
Benefits And Costs

A new methodology is proposed to establish practical guidelines for four incremental left-turn treatments: ( a) permissive single left-turn lane, ( b) protected–permissive single left-turn lane, ( c) protected dual left-turn lanes with equal lane use, and ( d) protected dual left-turn lanes with unequal lane use. Decision boundaries were derived from the equilibrium at which the delays of two incremental treatments were equal. The benefits and costs associated with different left-turn treatments—including safety impact and construction and maintenance costs—also were considered. These benefits and costs effectually shift the boundary curves for more realistic decision making.

Operational Effects of the Consolidated Intersection Design on Urban and Suburban Arterials

2018 ◽  
Vol 2672 (17) ◽  
pp. 96-107
Author(s):  
Daniel J. Cook
Keyword(s):  
Travel Time ◽  
Signalized Intersections ◽  
Signal Timing ◽  
Left Turn ◽  
Vehicle Delay ◽  
Cycle Lengths ◽  
Expected Benefits ◽  
Traffic Signal Timing ◽  
Critical Phases ◽  
Pedestrian Crossing

Along urban and suburban arterials, closely-spaced signalized intersections are commonly used to provide access to adjacent commercial developments. Often, these signalized intersections are designed to provide full access to developments on both sides of the arterial and permit through, left-turn, and right-turn movements from every intersection approach. Traffic signal timing is optimized to reduce vehicle delay or provide progression to vehicles on the arterial, or both. However, meeting both of these criteria can be cumbersome, if not impossible, under high-demand situations. This research proposes a new design that consolidates common movements at three consecutive signalized intersections into strategic fixed locations along the arterial. The consolidation of common movements allows the intersections to cycle between only two critical phases, which, in turn, promotes shorter cycle lengths, lower delay, and better progression. This research tested the consolidated intersection concept by modeling a real-world site in microsimulation software and obtaining values for delay and travel time for multiple vehicle paths along the corridor and adjacent commercial developments in both existing and proposed conditions. With the exception of unsignalized right turns at the periphery of the study area, all non-displaced routes showed a reduction in travel time and delay. Additional research is needed to understand how additional travel through the commercial developments adjacent to the arterial may effect travel time and delay. Other expected benefits of the proposed design include a major reduction in conflict points, shorter pedestrian crossing and wait times, and the opportunity to provide pedestrian refuge areas in the median.

Estimating Queue Length for Contraflow Left-Turn Lane Design at Signalized Intersections

2019 ◽  
Vol 145 (6) ◽  
pp. 04019020 ◽  
Author(s):  
Pan Liu ◽  
Jiaming Wu ◽  
Huaguo Zhou ◽  
Jie Bao ◽  
Zhao Yang
Keyword(s):  
Queue Length ◽  
Signalized Intersections ◽  
Left Turn
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