scholarly journals An Innovative Signal Timing Strategy for Implementing Contraflow Left-Turn Lanes at Signalized Intersections with Split Phasing

2021 ◽  
Vol 13 (11) ◽  
pp. 6307
Author(s):  
Rongwei Guo ◽  
Jinli Liu ◽  
Yi Qi
Keyword(s):  
Traffic Simulation ◽  
Design Procedure ◽  
Signalized Intersections ◽  
Signal Timing ◽  
Current Signal ◽  
Clearance Time ◽  
Left Turn ◽  
Simulation Based ◽  
Time Requirements

Contraflow Left-Turn Lanes (CLLs) have the potential of being a solution for mitigating congestions at signalized intersections where split phasing is recommended or required. However, the current signal timing strategy for the intersections with CLLs cannot be directly applied at the signalized intersections with split phasing (SIWSP). To address this problem, this study proposed an innovative signal timing strategy, which is referred to as Counterclockwise Split Phasing (CSP) signal timing, for implementing the CLLs at the SIWSPs. A traffic simulation-based case study was conducted and the results indicate that, by using the proposed CSP signal timing plan, CLLs can be implemented at the SIWSP and can significantly reduce the traffic congestions caused by the high left-turn demand at this type of intersection. In addition, since the proposed CSP signal timing design procedure has fully considered the clearance time requirements for the left-turn vehicles on the CLLs, the risk associated with the use of CLLs can be controlled which makes it safe to use this innovative intersection design at SIWSPs.

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.

Safety-Based Left-Turn Phasing Decisions for Signalized Intersections

2017 ◽  
Vol 2619 (1) ◽  
pp. 13-19 ◽  
Author(s):  
Kiriakos Amiridis ◽  
Nikiforos Stamatiadis ◽  
Adam Kirk
Keyword(s):  
Urban Areas ◽  
Primary Objective ◽  
Signalized Intersections ◽  
Safety Performance ◽  
Signal Timing ◽  
Left Turn ◽  
Crash Data ◽  
Intersection Safety ◽  
Traffic Volumes

The efficient and safe movement of traffic at signalized intersections is the primary objective of any signal-phasing and signal-timing plan. Accommodation of left turns is more critical because of the higher need for balancing operations and safety. The objective of this study was to develop models to estimate the safety effects of the use of left-turn phasing schemes. The models were based on data from 200 intersections in urban areas in Kentucky. For each intersection, approaches with a left-turn lane were isolated and considered with their opposing through approach to examine the left-turn–related crashes. This combination of movements was considered to be one of the most dangerous in intersection safety. Hourly traffic volumes and crash data were used in the modeling approach, along with the geometry of the intersection. The models allowed for the determination of the most effective type of left-turn signalization that was based on the specific characteristics of an intersection approach. The accompanying nomographs provide an improvement over existing methods and warrants and allow for a systematic and quick evaluation of the left-turn phase to be selected. The models used the most common variables that were already known during the design phase, and they could be used to determine whether a permitted or protected-only phase would suit the intersection when safety performance was considered.

scholarly journals DEVELOPMENT AND EVALUATION OF A QUICK METHOD FOR OPTIMIZING A SPACE AND SIGNAL TIMING PLAN FOR ISOLATED SIGNALIZED INTERSECTIONS

Transport ◽  
2020 ◽  
Vol 0 (0) ◽  
pp. 1-12
Author(s):  
Nedal Ratrout ◽  
Khaled Assi
Keyword(s):  
Signalized Intersections ◽  
Signal Timing ◽  
Quick Method ◽  
Traffic Demand ◽  
Optimization Software ◽  
Space And Time ◽  
Plan Optimization ◽  
New Models ◽  
Volume Characteristics

One major cause of congestion at intersections is the fluctuation of traffic demand during the day. This phenomenon necessitates developing new models that can be used to enhance the performance of signalized intersections. We suggest a quick procedure for optimizing signal timing plans after identifying the best phasing scheme and selecting optimal lane allocation (space optimization) for any volume characteristics during the day at a typical four-leg intersection. The main contribution of this study is developing a method for collectively optimizing a signal-timing plan, intersection space, and phasing scheme. TRANSYT-7F, SYNCHRO and HCS2010 were used to assess the developed models in a case study. It was found that regardless of the optimization software used for timing-plan optimization, optimizing both space and timing plan together produce significant reductions in average intersection delay compared to optimizing only the timing plan. Furthermore, this study showed that the developed model, which optimizes space and time, consistently provided better results in terms of average intersection delay compared to TRANSYT-7F, SYNCHRO and HCS2010 in the case study.

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.

Intersection Operation with Non-Traditional Dynamic Lane Scheme through Vehicle-to-Signal Connection

2019 ◽  
Vol 2673 (8) ◽  
pp. 322-332
Author(s):  
Sida Luo ◽  
Yu (Marco) Nie ◽  
Lin Zhu
Keyword(s):  
Integer Program ◽  
Signalized Intersections ◽  
Mixed Integer ◽  
Mixed Integer Program ◽  
Time Signal ◽  
Signal Timing ◽  
Left Turn ◽  
Intersection Operation ◽  
Lane Utilization ◽  
Near Future

This paper proposes an information-based dynamic lane (IDYL) scheme for signalized intersections with exclusive left-turn phases. Similar to the tandem design, the proposed scheme aims to increase the capacity of an isolated intersection by sorting incoming vehicles based on their turning movements. Its novelty is to guide vehicles of different movements into pre-designated dynamic lanes without stopping them via pre-signal. The assumption is that vehicles themselves or their drivers have access to, and can act on, real-time signal timing information through vehicle-to-signal connection to select the correct lane to enter as they approach the intersection. A mixed integer program is proposed to optimize jointly the lane configuration, timing plan, and dynamic lane utilization for an intersection. Results from numerical and simulation experiments show that IDYL can increase the reserve capacity by more than 25% when implemented on all legs of a standard four-leg intersection, and reduce the delay by around 15% when implemented on two opposing legs. The results from this study could help traffic engineers to operate signalized intersections with dynamic lanes when vehicle-to-signal connection becomes widely available in the near future.

Impacts of Changing from Permissive/Protected Left-Turn to Protected-Only Phasing: Case Study in the City of Tucson, Arizona

2019 ◽  
Vol 2673 (4) ◽  
pp. 616-626
Author(s):  
Xiaofeng Li ◽  
Alexander Weber ◽  
Adrian Cottam ◽  
Yao-Jan Wu
Keyword(s):  
Data Driven ◽  
Sensor Data ◽  
Signal Timing ◽  
Delay Model ◽  
Safety Measures ◽  
Trade Off ◽  
Near Misses ◽  
Left Turn ◽  
The City

Recent research has focused on the safety or mobility impacts of signal timing. Several studies have compared the choice between a protected-only left turn (PO) and a protected-permissive left turn (PPLT). However, few have compared both the safety and mobility impacts, and their tradeoffs. This study proposed data-driven methods to conduct a pilot study at an intersection in Tucson, Arizona. This study evaluated the impacts on vehicular mobility and multi-modal safety when changing from a PPLT to a PO. First, the daily and annual delay for the through and left-turn movements for the intersection was evaluated using a calibrated delay model and year-long 15-min traffic sensor data. Then, real-world near misses between cyclists, pedestrians, and vehicles were manually collected and analyzed using 48 h of videos. Last, both mobility and safety measures were converted into an annual cost to determine the trade-off between the before (PPLT) and the after (PO) situations. The results of this study demonstrate the feasibility of the proposed methods, providing practitioners with different options to evaluate left-turn phasing strategies effectively and efficiently.

Risk to Bicyclists in a Separated Path from Left Turns across Multiple Lanes: A Case for Protected-Only Left Turns

2021 ◽  
pp. 036119812110107
Author(s):  
Ray Saeidi Razavi ◽  
Peter G. Furth
Keyword(s):  
Opposite Direction ◽  
Signalized Intersections ◽  
Left Turn ◽  
The Road ◽  
Turn On ◽  
Road Users ◽  
Green Ball ◽  
Left Turns ◽  
The Right

At signalized intersections, permitted left turns (i.e., on a green ball, after yielding) across multiple through lanes and across a separated bike lane or bike path present a threat to bicyclist safety. A conflict study of two such intersections with a bidirectional bike path found that when cyclists cross while a vehicle is ready to turn left and there is no opposing through traffic to block it, the chance of the left-turning motorist yielding safely was only 9%, and the chance of their yielding at all—including yielding only after beginning the turn, then stopping in the opposing through lanes—was still only 37%. Motorist non-yielding rates were worse toward bikes arriving during green, toward bikes approaching from the opposite direction (i.e., riding on the right side of the road), and toward bikes facing a queue with multiple left turning vehicles. Of 112 cyclists who arrived on green when there was at least one left-turning car, but no opposing through traffic blocking it, 73 had to slow or stop to avoid a collision. Although these conflicts could be essentially eliminated using protected-only left turn phasing (turn on green arrow), common existing criteria prefer permitted left turns to reduce vehicular delay. A case study shows how, by considering multiple signalization alternatives, it can be possible to convert left turns to protected-only phasing without imposing a substantial delay burden on vehicles or other road users.

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.

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