Arterial Bandwidth Maximization via Signal Offsets and Variable Speed Limits Control

International audienceThe problem of maximizing bandwidth along an arterial is here addressed by use of two combined control actions: traffic lights offsets and variable speed limits. The optimization problem has been enriched in order to account for traffic energy consumption and network travel time, thus avoiding impractical or undesirable solutions. A traffic microscopic simulator has been used to assess the performance of the proposed technique in terms of energy consumption, travel time, idling time, and number of stops. The theoretical bandwidth proves to be well correlated with idling time and number of stops, while the variable speed limits control shows interesting advantages in terms of energy consumption without penalizing the travel time. An analysis of the Pareto optimum has been carried out to help the designer choose a trade-off in the multi-objective optimization

Arterial Bandwidth Maximization via Signal Offsets and Variable Speed Limits Control

International audienceThe problem of maximizing bandwidth along an arterial is here addressed by use of two combined control actions: traffic lights offsets and variable speed limits. The optimization problem has been enriched in order to account for traffic energy consumption and network travel time, thus avoiding impractical or undesirable solutions. A traffic microscopic simulator has been used to assess the performance of the proposed technique in terms of energy consumption, travel time, idling time, and number of stops. The theoretical bandwidth proves to be well correlated with idling time and number of stops, while the variable speed limits control shows interesting advantages in terms of energy consumption without penalizing the travel time. An analysis of the Pareto optimum has been carried out to help the designer choose a trade-off in the multi-objective optimization

Speed Advisory and Signal Offsets Control for Arterial Bandwidth Maximization and Energy Consumption Reduction

International audienceThe problem of maximizing bandwidth along anarterial is addressed here by use of two combined control actions:traffic light offsets and recommended speeds. The optimizationproblem has been enriched in order to account for traffic energyconsumption and network travel time, thus avoiding impracticalor undesirable solutions. A traffic microscopic simulator has beenused to assess the performance of the proposed technique in termsof energy consumption, travel time, idling time, and number ofstops. The correlation of theoretical bandwidth with known trafficperformance metrics is studied, and an analysis of the Paretooptimum has been carried out to help the designer choose atradeoff in the multiobjective optimization. Finally, an evaluationof the traffic performance at different levels of traffic demandaims at showing the best operation conditions of the proposedstrategy. A demand-dependent optimization is proposed

Forecast based traffic signal coordination using congestion modelling and real-time data

This dissertation focusses on the implementation of a Real-Time Simulation-Based Signal Coordination module for arterial traffic, as proof of concept for the potential of integrating a new generation of advanced heuristic optimisation tools into Real-Time Traffic Management Systems. The endeavour represents an attempt to address a number of shortcomings observed in most currently marketed on-line signal setting solutions and provide better adaptive signal timings. It is unprecedented in its use of a Genetic Algorithm coupled with Continuous Dynamic Traffic Assignment as solution evaluation method, only made possible by the recently presented parallelisation strategies for the underlying algorithms. Within a fully functional traffic modelling and management framework, the optimiser is developed independently, leaving ample space for future adaptations and extensions, while relying on the best available technology to provide it fast and realistic solution evaluation based on reliable real-time supply and demand data. The optimiser can in fact operate on high quality network models that are well calibrated and always up-to-date with real-world road conditions; rely on robust, multi-source network wide traffic data, rather than being attached to single detectors; manage area coordination using an external simulation engine, rather than a na¨ıve flow propagation model that overlooks crucial traffic dynamics; and even incorporate real-time traffic forecast to account for transient phenomena in the near future to act as a feedback controller. Results clearly confirm the efficacy of the proposed method, by which it is possible to obtain relevant and consistent corridor performance improvements with respect to widely known arterial bandwidth maximisation techniques under a range of different traffic conditions. The computational efforts involved are already manageable for realistic real-world applications, and future extensions of the presented approach to more complex problems seem within reach thanks to the load distribution strategies already envisioned and prepared for in the context of this work

Advances in genetic algorithm optimization of traffic signals

Recent advances in the optimization of fixed time traffic signals have demonstrated a move towards the use of genetic algorithm optimization with traffic network performance evaluated via stochastic microscopic simulation models. This dissertation examines methods for improved optimization. Several modified versions of the genetic algorithm and alternative genetic operators were evaluated on test networks. A traffic simulation model was developed for assessment purposes. Application of the CHC search algorithm with real crossover and mutation operators were found to offer improved optimization efficiency over the standard genetic algorithm with binary genetic operators. Computing resources are best utilized by using a single replication of the traffic simulation model with common random numbers for fitness evaluations. Combining the improvements, delay reductions between 13%-32% were obtained over the standard approaches. A coding scheme allowing for complete optimization of signal phasing is proposed and a statistical model for comparing genetic algorithm optimization efficiency on stochastic functions is also introduced. Alternative delay measurements, amendments to genetic operators and modifications to the CHC algorithm are also suggested

Integrated Freeway and Arterial Traffic Control to Improve Freeway Mobility without Compromising Arterial Traffic Conditions Using Q-Learning

Freeway and arterial transportation networks are operated individually in most cities nowadays. The lack of coordination between the two increases the severity of traffic congestion when they are heavily loaded. To address the issue, we propose an integrated traffic control strategy that coordinates freeway traffic control (variable speed limit control, lane change recommendations, ramp metering) and arterial signal timing using Q-learning. The agent is trained offline in a single-section road network first, and then implemented online in a large simulation network with real-world traffic demands. The online data are collected to further improve the agent's performance via continuous learning. We observe significant reductions in freeway travel time and number of stops and a slight increase in on-ramp queue lengths by implementing the proposed approach in scenarios with traffic congestion. Meanwhile, the queue lengths of adjacent arterial intersections are maintained at the same level. The benefits of the coordination mechanism is verified by comparing the proposed approach with an uncoordinated Q-learning algorithm and a decentralized feedback control strategy.Comment: 12 pages, 10 figures, 5 table

MULTI-MODAL SIGNAL PROGRESSION DESIGN FOR ARTERIALS WITH HEAVY TURNING FLOWS

Most urban commuters have long been plagued by congestion in traffic networks and the resulting impacts on safety as well as travel time uncertainties. Since such undesirable traffic conditions in urban arterials are mainly at intersections, traffic researchers often rely on various signal control strategies to smooth traffic flows and minimize excessive delays. Although the advance in communications and control technologies over the past decades has enabled the traffic community to progress significantly on this regard, much, however, remains to be done to achieve the goal of having an efficient and safe traffic environment. Hence, this study has developed an integrated multi-modal signal progression system that allows the traffic engineers to apply different modules of the developed system to produce the best set of signal control plans that can effectively work under various constraints associated with arterial traffic patterns and roadway geometric features. The first primary function of the developed arterial progression system is designed to maximize the progression efficiency of passenger cars on a long arterial comprising heavy left-turn volumes, limited turning bay length, and near-saturated intersections. The developed system with such an embedded function can produce concurrent progression for both the through and left-turn movements with the least likelihood of incurring mutual blockage between them and uneven traffic queues among all critical locations on the arterial. To decompose a long arterial into the optimal number of control segments with well-connected and maximized progression bands, this study has further offered a function of a two-stage optimization process to tackle various critical issues that may prevent vehicles from progressing smoothly over the entire long arterial. To accommodate heavy passenger car and bus flows over an urban arterial and ensure the progression quality for both modes, this study has advanced the system with an innovative function that can offer concurrent progression to the best selected mode(s) and direction(s), based on traffic volume, bus ratio, and geometric conditions. By weighting the progression bandwidth with the passenger volumes and taking into account all critical issues that may result in their mutual impedance, such an embedded function of the developed arterial control system can achieve the objective of maximizing the benefit for all roadway users and for all modes. Most importantly, to ensure the effectiveness of the developed system’s key functions under various arterial traffic patterns and control objectives, this study has integrated all key modules developed for, such as, the arterial signal design, allowing users to contend with most challenging scenarios, concurrently decomposing a long arterial into the optimal number of control segments for both modes, maximizing their progression bands within their respective segments, circumventing all geometric constraints, and balancing the progression length and bandwidth between the competing modes. In view of computing efficiency associated with the execution of all interrelated optimizing functions, this study has also designed a customized algorithm to minimize all computation-related tasks. Rigorous evaluation with extensive numerical studies has verified the effectiveness of the developed arterial system’s key functions, and evidenced their contributions with respect to offering best progression and minimizing traffic delays. The developed system’s flexibility in circumventing various roadway constraints and traffic queue spillback has also been confirmed from the results of comprehensive simulation experiments with different critical traffic scenarios

Dynamisch-netzwerkweite Lichtsignalanlagenoptimierung

Nowadays, many cities in the world are suffering from problems like congestion, pollution, and traffic accidents which are caused by vehicular traffic. The correct scheduling of traffic lights can help to alleviate these problems by improving the flow of vehicles through the cities. The main aim of this dissertation is to build an approach to find the good traffic signal plans for a large area. The two major features of the approach developed in this thesis are real-time and system-wide. Since traffic flow changes with the time of day, the real-time computation of the traffic signal plans can improve the operation efficiency of traffic lights compared with fixed signal plans which is an old but still often used technology in the world. The proposed approach is the serial optimization with a hierarchical control framework. The upper level is the level for macro control strategies including a network partition strategy and a network signal coordination strategy. The network partition strategy means that the urban network is partitioned into smaller sub networks based on the network's topological graph and intersections' priority order. The priority order is computed by the sorting model of priority order (SMoPO), which offers the opportunity for the higher priority intersection to be coordinated earlier and to obtain more benefit. The network signal coordination strategy is developed to determine which intersections form a coordination pair and which traffic streams need to be coordinated. This strategy converts the optimization problem into a much simpler one. The number of operations and the computation time to solve this optimization problem drops largely. The lower level is the level for micro parameters calculation, in which a method for the computation of the optimal relative offsets is proposed which is based on cyclic flow profiles. All of the developed strategies were programed and interfaced with the microscopic simulation tool "SUMO". To verify the success and the dynamic feasibility of strategies, the computation speed tests were done in three-by-three to sixty-by-sixty grid nets to demonstrate the real-time feasibility of the approach. After that, microsimulation studies have been performed to evaluate the performance of the strategies. The first case study was a hypothetic eight-by-eight grid net with varied traffic demands and link lengths, and the results revealed that the strategy was effective when the intersections were not oversaturated. The others were two real networks in Braunschweig City, whose input data was from the Project AIM (Application platform Intelligent Mobility). The simulation results showed the delay time was decreased on average in both cases compared to Webster's model.Der motorisierte Individualverkehr führt in fast allen großen Städten der Welt zu Staus, Umweltverschmutzung und Unfällen. Eine gute Anpassung der Steuerprogramme von Lichtsignalanlagen (LSA) an die jeweilige Verkehrssituation kann dazu beitragen, den Verkehrsablauf flüssiger, weniger umweltbelastend und sicherer zu gestalten. Das Hauptziel dieser Arbeit ist die Entwicklung eines Verfahrens, welches diese Anpassung auch für gro?e Städte mit einer Vielzahl von LSAs ermöglicht. Diese Arbeit folgt dabei zwei Zielvorgaben. Das zu entwickelnde System soll realzeitfähig sein und auch große Städte mit einigen tausend LSA versorgen können. Die Realzeitkomponente ist von Bedeutung, weil die verkehrliche Nachfrage sehr starken und teilweise nicht vorhersehbaren Schwankungen unterliegt. Von einem solchen adaptiven Verfahren kann erwartet werden, dass es effizienter ist als die Festzeitsteuerungen, die noch immer in vielen Teilen der Welt benutzt werden. In dieser Arbeit wurde zu diesem Zweck ein serielles Optimierungsverfahren entwickelt, das in ein hierarchisches Steuerungsrahmenwerk eingebunden ist. Die übergeordnete Ebene enthält ein Verfahren, mit dessen Hilfe ein Netzwerk in Teilnetze zerlegt werden kann. Dieses Verfahren basiert auf dem topologischen Graphen des Netzwerkes und der Prioritätenfolge der Kreuzungen des Netzwerks. Die Prioritätenfolge wird durch das in dieser Arbeit entwickelte Verfahren Sorting Model of Priority Order (SMoPO) berechnet, mit dessen Hilfe festgelegt wird, wann im Laufe des Optimierungsprozesses welche Kreuzung optimiert wird - Kreuzungen mit einer höheren Priorität zuerst, die weniger wichtigen später. Darüber hinaus wurde für diese Ebene ein Koordinierungsverfahren entwickelt, mit dem bestimmt werden kann, welche Paare von Kreuzungen jeweils zu koordinieren sind. Dieser Ansatz reduziert die Komplexität dieses Optimierungsproblems dramatisch, weil es eine Unterteilung eines großen Problems in viele kleinere ermöglicht. Die untere Ebene dieses Rahmenwerkes ist die Berechnung der Mikroparameter der einzelnen Kreuzung. Die optimalen Offsets werden mit Hilfe einer Methode berechnet, die auf zyklischen Flussprofilen basiert. Alle in der Arbeit entwickelten Verfahren wurden in Computerprogrammen umgesetzt und mit einer Schnittstelle zu dem mikroskopischen Verkehrssimulationstool "SUMO" versehen. Um die Realzeitfähigkeit der Strategien zu überprüfen, wurden Geschwindigkeitstests für Drei-mal-Drei bis Sechzig-mal-Sechzig Quadratgitternetze durchgeführt. Anschließend wurden mehrere Fallstudien mit SUMO durchgeführt, um die Qualität des neuen Verfahrens zu evaluieren. Die erste Fallstudie war ein künstliches Acht-mal-Acht Quadratgitternetz mit variierender Verkehrsnachfrage und Kantenlängen. Die Ergebnisse haben gezeigt, dass die Strategie effektiv ist, wenn die Kreuzungen nicht übersättigt sind. Die anderen Fallbeispiele waren zwei echte Netze aus dem Braunschweiger Stadtgebiet mit Inputdaten aus dem Projekt AIM (Anwendungsplattform Intelligente Mobilität). Auch hier konnte die neue Strategie die Verlustzeiten in beiden Fällen im Vergleich zum Webster-Modell verringern

MAXBAND Version 3.1: Heuristic and optimal approach for setting the left turn phase sequences in signalized networks

The main objective of synchronized signal timing is to keep traffic moving along arterials in platoons throughout the signal system by proper setting of left turn phase sequence at signals along the arterials/networks. The synchronization of traffic signals located along the urban/suburban arterials in metropolitan areas is perhaps one of the most cost-effective methods for improving traffic flow along these streets. MAXBAND Version 2.1 (formerly known as MAXBAND-86), a progression-based optimization model, is used for generating signal timing plan for urban networks. This model formulates the problem as a mixed integer linear program and uses Land and Powell branch and bound search to arrive at the optimal solution. The computation time of MAXBAND Version 2.1 tends to be excessive for realistic multiarterial network problems due to the exhaustive nature of the branch and bound search technique. Furthermore, the Land and Powell branch and bound code is known to be numerically unstable, which results in suboptimal solutions for network problems with a range on the cycle time variable. This report presents the development of a new version of MAXBAND called MAXBAND Version 3.1. This new version has a fast heuristic algorithm and a fast optimal algorithm for generating signal timing plan for arterials and networks. MAXBAND 3.1 can generate optimal/near-optimal solutions in fraction of the time needed to compute the optimal solution by Version 2.1. The heuristic algorithm in the new model is based on restricted search using branch and bound technique. The algorithm for generating the optimal solution is faster and more efficient than version 2.1 algorithm. Furthermore, the new version is numerically stable. The efficiency of the new model is demonstrated by numerical results for a set of test problems