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The left-turn of vehicles at intersections has significant impacts on urban traffic congestions and accidents, which have negative effect on vehicle emissions causing air pollution. Many urban traffic networks prohibit direct left-turns for transport planning to keep traffic moving efficiently on major roads. As such, this paper proposes a bi-level mathematical model for left-turn prohibition planning considering both travel times and traffic emissions. The lower-level and upper-level are respectively solved by using the Frank-Wolfe algorithm and an improved genetic algorithm. By numerical examples, this paper shows that the improved algorithm can effectively enhance the speed and accuracy of the calculation, and the traffic congestions and emissions can be alleviated by implementing the left-turn prohibition at some carefully selected intersections.

Left turns may generate efficiency problems, which can be solved by appropriately prohibiting left turns. The goal of this paper is to propose a method for purpose of minimizing total travel times in urban road networks by prohibiting left turns. With left turn prohibition, the signal timing plan is optimized with the lane- based method because the method can adequately handle both signal timing optimization and lane assignment. The total travel time is calculated with link flows and link travel time being estimated with signal settings. As illustrated by numerical examples, prohibiting left turns reduces the total travel time of car traffic in road networks. As the left turn prohibition results can handle the randomness in the network, these results provide potential implications for congestion management.Key words: left turn prohibition, lane-based signal optimization, turning restriction, stochastic user equilibrium, left turn treatment.Les virages a gauche peuvent entrainer des problemes d'efficacite qui peuvent etre resolus en interdisant de maniere ciblee les virages a gauche. Le but de cette etude est de proposer une methode en vue de minimiser la duree totale du deplacement sur les reseaux routiers urbains en interdisant les virages a gauche. Au moyen de l'interdiction du virage a gauche, le plan de synchronisation de la signalisation est optimise a l'aide de la methode en fonction des voies, car celle-ci peut adequatement gerer l'optimisation de la synchronisation de signalisation et l'affectation des voies. La duree totale de deplacement est calculee en estimant les debits de liaisons et la duree de deplacement sur les liaisons, et ce, a l'aide de parametres de signalisation. D'apres les exemples numeriques, l'interdiction des virages a gauche permet de reduire la duree totale de deplacement pour la circulation automobile sur les reseaux routiers. Puisque les resultats d'interdiction de virage a gauche montrent la capacite de traiter le caractere stochastique du reseau, ces resultats fournissent des repercussions possibles au niveau de la gestion de la congestion. [Traduit par la Redaction]Mots-cles: interdiction de virage a gauche, optimisation de la signalisation en fonction des voies, interdiction de virage, equilibre d'utilisateur stochastique, traitement de virage a gauche., 1. IntroductionLeft turn movements may have negative impacts on the efficiency of signalized urban networks if they were not well accommodated. Permitted left turns are one of the most hazardous [...]

Urban road networks may benefit from left turn prohibition at signalized intersections regarding capacity, for particular traffic demand patterns. The objective of this paper is to propose a method for minimizing the total travel time by prohibiting left turns at intersections. With the flows obtained from the stochastic user equilibrium model, we were able to derive the stage generation, stage sequence, cycle length, and the green durations using a stage-based method which can handle the case that stages are sharing movements. The final output is a list of the prohibited left turns in the network and a new signal timing plan for every intersection. The optimal list of prohibited left turns was found using a genetic algorithm, and a combination of several algorithms was employed for the signal timing plan. The results show that left turn prohibition may lead to travel time reduction. Therefore, when designing a signal timing plan, left turn prohibition should be considered on a par with other left turn treatment options.

Urban road networks may benefit from left turn prohibition at signalized intersections regarding capacity, for particular traffic demand patterns. The objective of this paper is to propose a method for minimizing the total travel time by prohibiting left turns at intersections. With the flows obtained from the stochastic user equilibrium model, we were able to derive the stage generation, stage sequence, cycle length, and the green durations using a stage-based method which can handle the case that stages are sharing movements. The final output is a list of the prohibited left turns in the network and a new signal timing plan for every intersection. The optimal list of prohibited left turns was found using a genetic algorithm, and a combination of several algorithms was employed for the signal timing plan. The results show that left turn prohibition may lead to travel time reduction. Therefore, when designing a signal timing plan, left turn prohibition should be considered on a par with other left turn treatment options. [ABSTRACT FROM AUTHOR]

Recurring congestion at signalized intersections is caused by the inability of traffic signal controls to serve demand even in cities where advanced traffic signal timing and management systems are in operation. Left-turn prohibition (LTP) and partial grade separation with low-clearance underpass (LCUP) are possible congestion mitigation actions for urban complex and congested signalized intersections that have exhausted other options for capacity enhancement, such as lane addition and signal timing optimization. LTP and LCUP improve traffic signal efficiency by eliminating signal phases, increasing green splits, or adding lanes. They also improve intersection safety by eliminating certain conflicts. At the same time, they necessitate traffic rerouting, may have negative impacts at downstream locations, and may have perceived or actual impacts to accessibility and neighborhood character. A planning-level assessment method to quantify and compare the benefits and costs LTP and LCUP was developed to examine the potential feasibility of these congestion mitigation actions prior to conducting, e.g., extended data collection, detailed analysis, simulation, evaluation, and public meetings. The assessment considers intersection delays, accident frequency, and cost-benefit analysis based on industry publications. The proposed method uses standard methodology and nationally accepted default values and conservative assumptions to expedite assessment by minimizing the number of required inputs. Due to the complexity of analysis for LTP and LCUP for various time periods and multiple locations, a spreadsheet-based tool was developed. A case study demonstrates the combined use of travel time, safety, and economic savings of the proposed method. [ABSTRACT FROM AUTHOR]

Enhancing traffic flow plays an important role in the traffic management of urban arterial networks. The policy of prohibiting left-turn (PLT) at selected highly demanded intersections has been adopted as an attempt to increase the efficiency at these intersections. In this paper, we study the impact of PLT by mathematical analysis and simulations based on the cellular automaton model. Using the flow-density relation, three system performance indexes are examined: the average trip completion rate, the average traffic flow, and the average velocity of vehicles. Different route guidance strategies, including the shortest path and the quickest path, are investigated. We show that when left turn is prohibited, vehicles are distributed more homogeneously in the road network, and the system performs better and reaches a higher capacity. We also derive a critical length of link, above which the benefit of PLT will decrease. [ABSTRACT FROM AUTHOR]

This study analyses intersection configuration design elements associated with traffic-related air pollution and ranks the three most effective configurations. An assessment methodology for pedestrians PM exposure associated with crossing traffic hotspots is presented. The quantitative PM exposure concentration reduction effects of at-grade intersection design with stretched segment, pedestrian bridge and left-turn prohibition are estimated using a new US Environmental Protection Agency general emissions model: a multi-link dispersion model based on the AERMOD model. The results of the case study show that intersection design using a stretched segment has a reverse effect on pedestrian PM exposure, while the left-turn prohibition and the pedestrian bridge are environmentally friendly options with lower PM concentrations. In order of effectiveness, the intersection design types can be listed as pedestrian bridge, left-turn prohibition and stretched segment, based on the pedestrian PM exposure index. This study proposes guidelines and tools that road/intersection designers and engineers can use for quantifying environmental impacts. It also shows that design configurations have the potential to mitigate air quality impacts from traffic. [ABSTRACT FROM AUTHOR]

Efficient operations at intersections are associated with smooth, safe, and sustainable travel at the network level. It is often challenging to prevent congestion at these locations, especially during rush hours, owing to high traffic demand and restraints of road geometry. The primary cause of intersection traffic congestion is large variations and fluctuations in traffic demand during the day. Dynamic lane assignment (DLA) is an intelligent transportation system (ITS) technology that can improve traffic operations at signalized intersections, making better use of available space by optimizing lane allocation based on real-time fluctuating traffic demands. This study used a bruteforce optimization model to produce a vast synthetic dataset of turning movements at a four-legged signalized intersection. The model then found the optimal lane assignment and cycle length for each case. The produced data were used to develop a deep learning model to predict the optimal lane assignment and cycle length simultaneously at any four-legged signalized intersection without applying optimization software per se. The deep learning model results developed were compared with the results of the k-nearest neighbors (KNN), random forest, and decision tree algorithms. It was found that the deep learning model was superior, with accuracy and F1 score of 95.26% and 93.56%, respectively. The proposed solution is expected to require insignificant additional resources and services for successful implementation, particularly in developing countries. [ABSTRACT FROM AUTHOR]

Road intersections play an important role in the operation of an urban road transportation system. However, channelized segment (C-segment) spillovers frequently occur during peak hours, making the vehicle queue on a lane spatially and temporally interact with the queue on another lane. Intersection traffic efficiency is thus largely degraded. Unfortunately, most of the existing models cannot capture the spatial-temporal queue interactions and thus are incapable of developing efficient intersection optimization plans. To fill this gap, the paper proposes a highly efficient approach traffic flow model to capture C-segment spillovers. An optimization problem that takes C-segment spillovers into account is formulated as a nonlinear programming model, and it is solved by using a Markov chain Monte Carlo method. The proposed model and solution are tested in several scenarios with various intersection settings, and the effectiveness of the proposed models is demonstrated. This study is beneficial to understanding C-segment spillovers and the models can be applied to improve traffic efficiency at recurrently-congested intersections. [ABSTRACT FROM AUTHOR]

The lane closures caused by the work zone at the approaches create a negative impact on the operational effectiveness of the signalized intersections. This paper presents an innovative design for intersections with work zones to improve the intersection's practical capacity. In this design, the lanes in the leg with work zone can be used dynamically as approach and exit lanes during different periods of a signal cycle by using the pre-signal. An optimization model for an optimal geometric layout and signal timing design is built to capture real-world operational constraints, including the lane assignment, the signal timing of the main signal and pre-signal, the distance of the mixed-usage area and the transition area, and the degree of saturation restriction. A case study and extensive numerical analysis demonstrate the effectiveness of the prospective design as compared with conventional designs under different geometric layout and traffic demand situations. Overall, the proposed design can lead to an increment in the practical capacity of the intersection with a work zone (by up to 30%) and reduce the average vehicular delay accordingly (by 50%) without necessitating an expansion of the intersection. The results show that the promising application of the proposed design when the length of the work zone is less than 160 m. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vehicle movements at signalized intersections should follow the guidance of lane marking arrows. Turns are permitted or banned depending on the existence of lane marking arrows establishing network link connectivity. Lane markings are the interface that joins consecutive upstream and downstream intersections. Traffic flows from origins to destinations across intersections should be governed by lane markings. In this study, conventionally fixed lane markings are relaxed as binary variables to be optimized by maximizing the green bandwidths. The proposed methodology is innovative in that it extends the lane-based design framework to incorporate green band maximization for enhancing traffic signal coordination. Path flows are controlled to satisfy flow conservations and to compile turning flows at intersections. With these turning flows as inputs, lane markings can be optimized together with the coordinated traffic signal settings. Path flows, path travel times, and path choices are evaluated through new linear constraints. For path travel times, cruise times along lanes and total delays at the ends of lanes are evaluated. The non-linear total delays are approximated by the proposed linearized delay function. The model coefficients are calibrated by network data as in a previous study. The problem is formulated as a binary-mixed-integer-linear-program and solved by standard branch-and-bound techniques using a CPLEX solver. To avoid non-linearity in the problem formulation, the bandwidth maximization approach is adopted instead of minimizing the total network delay in the design of the signalized network. A network with four intersections is provided to demonstrate how optimized lane markings can create efficient network link configurations. The numerical results are promising compared with those obtained in previous studies and show that the overall network performance can be improved. [ABSTRACT FROM AUTHOR]

A comprehensive project evaluation and decision-making method considering multiple objectives, stakeholders, and attributes of proposed traffic treatments is inherently complicated. Although individual techniques in evaluating operations, safety, economic, and stakeholder objectives are available, a practical method that integrates all these risk factors and their uncertainties into a multi-attribute decision-making tool is absent. A three-level project decision-making process was developed to model and assess multiple-attribute risk in a proposed traffic treatment from the perspective of multiple stakeholders. The direct benefits from reducing delay and safety risk (basic objectives of traffic treatments) are computed in Level 1 with established methods. Feasibility and performance analysis in Level 2 examine site-specific constraints and conduct detailed performance analysis using advanced analysis tools. In Level 3, this paper introduces an innovative and integrated multiple attributes evaluation process under fuzziness and uncertainty (MAFU) process for evaluation and decision-making. The MAFU is a comprehensive and systematic assessment and decision-making procedure that can assess the magnitudes of project performance and to integrate conflicting interests and trade-offs among stakeholders. A case study illustrates the application of MAFU for the selection of a traffic alternative involving several evaluation attributes and stakeholders. Results show that the MAFU produced the smallest variance for each alternative. With traditional cost-benefit evaluation methods, the uncertainty associated with performance of a traffic project in terms of operation, safety, environmental impacts, etc., is unrestricted and cumulative. Therefore, a reliable multi-attribute evaluation of complex traffic projects should not be made with conventional cost-benefit analysis alone but with a process like MAFU. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Lane reorganization strategies such as lane reversal, one-way street, turning restriction, and cross elimination have demonstrated their effectiveness in enhancing transportation network capacity. However, how to select the most appropriate combination of those strategies in a network remains challenging to transportation professionals considering the complex interactions among those strategies and their impacts on conventional traffic control components. This article contributes to developing a mathematical model for a traffic equilibrium network, in which optimization of lane reorganization and traffic control strategies are integrated in a unified framework. The model features a bi-level structure with the upper-level model describing the decision of the transportation authorities for maximizing the network capacity. A variational inequality (VI) formulation of the user equilibrium (UE) behavior in choosing routes in response to various strategies is developed in the lower level. A genetic algorithm (GA) based heuristic is used to yield meta-optimal solutions to the model. Results from extensive numerical analyses reveal the promising property of the proposed model in enhancing network capacity and reducing congestion. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

In recent years, there has been major interest in “access management” as a new response to the ubiquitous traffic congestion problem. Among the different access management strategies is the idea of prohibiting left-turn movements at unsignalized driveways. In this study, the Corridor Simulation traffic simulation model was used to evaluate the operational impacts of different left-turn treatments at mid-block intersections on different classes of roadway facilities. The study also examined the impact of varying the arterial and driveway volume on the effectiveness of restricting direct left turns and providing alternative movements. Three different alternatives were considered for left-turn treatments at mid-block unsignalized intersections: (1) no restriction of direct left turns from or to driveways; (2) no direct left turns in or out of driveways and diverted traffic makes a U-turn at the next intersections; and (3) no direct left turns in or out of driveways and diverted traffic makes a U-turn at mid-block. Two additional cases were also evaluated: a jug handle design, and no direct left turns in or out of all-but-one driveways (concentrated left turn). The results show very little operational difference between the no restrictions on direct left turns alternative versus the restrictions with the U-turn alternative movements from site to site. The jughandle design appeared to be a superior alternative for accommodating left-turn deterred traffic for multilane divided and undivided sites compared to mid-block or intersection U-turns. In addition, it is shown that the concentrated left turn appears to be an excellent solution for improving traffic flow conditions. [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Civil Engineering is the property of Canadian Science Publishing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

OBJECTIVES: In urban settings, pedestrian fatalities and injuries are concentrated on major roads. This study aims to describe urban intersections with major roads (arterials and collector roads) and explore the association between intersection characteristics and injured pedestrians. METHODS: From a stratified random sampling in Montreal, Quebec, 512 intersections were selected and their characteristics collected. The number of injured pedestrians from 1999 to 2008 was obtained from ambulance services. Binomial negative regression models (including IRR: incidence rate ratios) were calculated to determine associations between intersection characteristics and injured pedestrians: i) at all intersections; ii) at intersections with multi-lane roads and iii) at signalized intersections with available vehicle and pedestrian counts. RESULTS: Major intersections had more traffic lanes (3.8 vs. 1.7, p < 0.01) and longer pedestrian crossings (18.8 m vs. 12.7 m, p < 0.01) than minor intersections. Bus stops were also more frequent at these intersections (75% vs. 6%, p < 0.01). Overall, each additional traffic lane was associated with a 75% increase in the number of injured pedestrians (IRR = 1.75; 95% confidence interval [CI] = 1.41-2.18). At intersections with multi-lane roads, a fourth branch (IRR = 2.40; 95% CI = 1.53-3.77), vehicles parked within 5 m of the intersection (IRR = 2.40; 95% CI = 1.64-3.51), and marked crosswalks (IRR = 1.79; 95% CI = 1.08-2.95) significantly increased the number of injured pedestrians. Raised medians had no significant protective effect. CONCLUSIONS: The results show that besides traffic and pedestrian volumes, intersection characteristics contribute to pedestrian injuries. The reduction of traffic lanes, parking prohibition near intersections and implementation of appropriate pedestrian refuge areas would improve pedestrian safety. KEY WORDS: Injuries; pedestrian; major roads; intersections; urban health Can J Public Health 2015;106(6):e388-e394 doi: 10.17269/CJPH.106.4821 OBJECTIFS: Decrire les intersections avec routes majeures (artere, collectrice) en milieu urbain, et explorer l'association entre les caracteristiques de ces intersections et le nombre de pietons blesses. METHODES: Les caracteristiques de 512 intersections (Montreal, Quebec), selectionnees via un echantillonnage aleatoire stratifie ont ete mesurees. Le nombre de pietons blesses provient des services ambulanciers (1999-2008). L'association entre les caracteristiques des intersections et le nombre de pietons blesses (RTI: rapports de taux d'incidence) a ete quantifie par des regressions binomiales negatives: 1) incluant toutes les intersections; 2) incluant les intersections de rues ayant plusieurs voies de circulation; 3) incluant les intersections pour lesquelles des comptages de vehicules et de pietons etaient disponibles. RESULTATS: Les intersections majeures ont davantage de voies de circulation (3,8 c. 1,7, p < 0,01) et des traverses pour pietons plus longues (18,8 mc. 12,7 m, p < 0,01) que les intersections de rues locales. Les arrets d'autobus y sont plus frequents (75 % c. 6 %, p < 0,01). Globalement, chaque voie additionnelle de circulation est associee a une augmentation de 75 % du nombre de pietons blesses (RTI = 1,75; IC95% = 1,41-2,18). Aux intersections de rues ayant plusieurs voies de circulation, une quatrieme branche (RTI = 2,40; IC95% = 1,53-3,77), la presence de vehicules stationnes a moins de 5 m de l'intersection (RTI = 2,40; IC95% = 1,64-3,51) et le marquage de passages pour pietons (RTI = 1,79; IC95% = 1,08-2,95) sont significativement associes a une augmentation du nombre de pietons blesses. CONCLUSION: Les resultats demontrent qu'au-dela des volumes de trafic et de pietons, les caracteristiques des intersections avec routes majeures contribuent au plus grand nombre de blesses pietons. La reduction des voies de circulation, l'interdiction de stationner pres des coins de rue et d'autres amenagements pertinents pourraient y ameliorer la securite des pietons en milieu urbain. MOTS CLES: blesses; pietons; arteres; intersections; sante urbaine, In 2010 in the United States, 4,280 pedestrians were killed and 70,000 were injured in traffic crashes. (1) In Quebec, every year over 3,000 pedestrians are injured, including about 1,400 [...]

ABSTRACT Any shortest path finding problem can be regarded as a design problem since it requires the design of an algorithm which can be implemented as an information system-based solution. [...]