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Contribuições para a análise e simulação de redes ópticas: aspectos de Engenharia de Tráfego, restauração dinâmica e conversão de comprimentos de onda; Contributions for the analysis and simulation of optical networks: aspects of traffic engineering, dynamic restoration and conversion of wavelenghts

Aloia, Eduardo José
Fonte: Biblioteca Digitais de Teses e Dissertações da USP Publicador: Biblioteca Digitais de Teses e Dissertações da USP
Tipo: Tese de Doutorado Formato: application/pdf
Publicado em 09/03/2009 PT
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46.3%
A tecnologia WDM (Wavelength Division Multiplexing) e a introdução de OXCs (Optical Cross Connect) e OADMs (Optical Add/Drop Multiplexer) puramente ópticos podem dotar as redes ópticas da função de networking, ou seja, da capacidade de manipular comprimentos de onda de forma a implementar o roteamento destes. Esta possibilidade implica em uma nova forma de relacionamento das aplicações com a camada física, sendo a arquitetura GMPLS candidata a estabelecer tal relacionamento. Soluções eficientes para o problema de alocação de recursos e roteamento de tráfego tornam-se uma necessidade imperiosa em projeto, expansão e gerenciamento de redes ópticas. A contribuição desta tese consiste em relacionar funcionalidades tais como: agregação (grooming) de tráfego, mecanismo de controle de admissão de chamadas (CAC), mecanismos de restauração e alocação de conversores em redes ópticas heterogêneas, avaliando-se as métricas de probabilidade de bloqueio, probabilidade do tráfego bloqueado e imparcialidade (fairness). Tais funcionalidades são tratadas separadamente na literatura. Com este objetivo em mente modela-se a rede com duas camadas: a camada física e a camada virtual. Estabelecem-se duas políticas de agregação de tráfego MrTV (minimização da rota na topologia virtual) e MrTF (minimização da rota na topologia física) e analisa-se o desempenho destas em relação à porcentagem de tráfego bloqueado. Em seguida um mecanismo de controle de admissão de chamadas (CAC) é implementado e sua influência em termos de imparcialidade (fairness) e probabilidade de bloqueio é analisada. A simulação e análise de redes ópticas...

Method for estimating railroad track settlements due to dynamic traffic loads

Queiroz, Rudney C.; Macari, Emir José
Fonte: Universidade Estadual Paulista Publicador: Universidade Estadual Paulista
Tipo: Conferência ou Objeto de Conferência Formato: 1769-1772
ENG
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This paper is the result of real-scale physical modeling study designed to simulate the load-deformation characteristics of railroad foundation systems that include the railroad ties, the ballast, and the sub-base layers of a railroad embankment. The study presents comparisons of the application of dynamic loads of 100kN on the rails, and the resulting deformations during a 500,000 cycle testing period for three rail support systems; wood, concrete and steel. The results show that the deformation curve has an exponential shape, with the larger portion of the deformation occurring during the first 50,000 load cycles followed by a tendency to stabilize between 100,000 to 500,000 cycles. These results indicate that the critical phase of deformations of a new railroad is within the first 50,000 cycles of loading, and after that, it slowly attenuates as it approaches a stable value. The paper also presents empirically derived formulations for the estimation of the deformations of the rail supports as a result of rail traffic.

Um modelo multifractal aplicado a predição de trafego de redes-proposta e avaliação; A multifractal traffic model with application in network traffic prediction proposal and evaluation

Gabriel Rocon Bianchi
Fonte: Biblioteca Digital da Unicamp Publicador: Biblioteca Digital da Unicamp
Tipo: Dissertação de Mestrado Formato: application/pdf
Publicado em 22/06/2005 PT
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A utilização de esquemas dinâmicos de controle de tráfego possibilita uma maior eficiência na utilização dos recursos da rede. A estrutura de correlação do tráfego fractal das modernas redes de comunicação pode ser explorada a fim de se implementar esquemas dinâmicos de controle de tráfego. Indispensáveis aos esquemas dinâmicos de controle, os preditores de tráfego podem ser obtidos a partir de modelos estatísticos que descrevam as características do tráfego das redes reais. Inicialmente, o presente trabalho inova ao propor uma extensão ao amplamente utilizado modelo tráfego Browniano fracionário, tornando-o apto a descrever não somente as características auto-similares, mas também as características multifractais do tráfego. Em seguida, supondo-se que as estatísticas do tráfego sejam modeladas através da extensão proposta ao modelo tráfego Browniano fracionário, uma proposta original de preditor de tráfego é apresentada. As avaliações realizadas mostram que a extensão proposta ao modelo tráfego Browniano fracionário é capaz de descrever o comportamento multifractal existente no tráfego das redes, proporcionando ganhos de modelagem e conduzindo a resultados de predição mais precisos; Dynamic traffic control mechanisms can improve network resource utilization. The fractal traffic correlation structure can be exploited for designing dynamic network control mechanisms. Playing the most important role in the dynamic control mechanisms...

Simple and stable dynamic traffic engineering for provider scale ethernet

Teixeira, António Edgar Carvalho
Fonte: Faculdade de Ciências e Tecnologia Publicador: Faculdade de Ciências e Tecnologia
Tipo: Dissertação de Mestrado
Publicado em //2010 ENG
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56.42%
Trabalho apresentado no âmbito do Mestrado em Engenharia Informática, como requisito parcial para obtenção do grau de Mestre em Engenharia Informática; The high speeds and decreasing costs of Ethernet solutions has motivated providers’ interest in using Ethernet as the link layer technology in their backbone and aggregation networks. Provider scale Ethernet offers further advantages, providing not only an easy to manage solution for multicast traffic, but also transparent interconnection between clients’ LANs. These Ethernet deployments face altogether different design issues, requiring support for a significantly higher number of hosts. This support relies on hierarquization, separating address and virtual network spaces of customers and providers. In addition, large scale Ethernet solutions need to grant forwarding optimality. This can be achieved using traffic engineering approaches. Traffic engineering defines the set of engineering methods and techniques used to optimize the flow of network traffic. Static traffic engineering approaches enjoy widespread use in provider networks, but their performance is greatly penalized by sudden load variations. On the other hand, dynamic traffic engineering is tailored to adapt to load changes. However...

Modeling Traffic Flow Emissions

Cappiello, Alessandra
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Formato: 4264953 bytes; application/pdf
EN_US
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The main topic of this thesis is the development of light-duty vehicle dynamic emission models and their integration with dynamic traffic models. Combined, these models constitute fundamental components to support the development and assessment of traffic management policies, and the optimization of their parameters, to alleviate the negative impacts of road traffic. We develop and implement a dynamic model of emissions (CO2, CO, HC, and NOx) and fuel consumption for light-duty vehicles. The model is derived from regression-based and load-based emissions modeling approaches, and effectively combines their respective advantages. The model is calibrated for two vehicle categories using FTP as well MEC01 driving cycles data. The US06 driving cycle is used to validate the estimation capabilities of the proposed model. The preliminary results indicate that the model gives reasonable results compared to actual measurements as well to results obtained with CMEM, a well-known load-based dynamic emission model. Furthermore, the results indicate that the model runs fast, and is relatively simple to calibrate. We propose a framework for the integration of dynamic emission models with nonmicroscopic dynamic traffic models...

Fluid Models for Traffic and Pricing

Kachani, Soulaymane; Perakis, Georgia
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 295629 bytes; application/pdf
EN_US
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Fluid dynamics models provide a powerful deterministic technique to approximate stochasticity in a variety of application areas. In this paper, we study two classes of fluid models, investigate their relationship as well as some of their applications. This analysis allows us to provide analytical models of travel times as they arise in dynamically evolving environments, such as transportation networks as well as supply chains. In particular, using the laws of hydrodynamic theory, we first propose and examine a general second order fluid model. We consider a first-order approximation of this model and show how it is helpful in analyzing the dynamic traffic equilibrium problem. Furthermore, we present an alternate class of fluid models that are traditionally used in the context of dynamic traffic assignment. By interpreting travel times as price/inventory-sojourn-time relationships, we are also able to connect this approach with a tractable fluid model in the context of dynamic pricing and inventory management. Finally, we investigate the relationship between these two classes of fluid models.; Singapore-MIT Alliance (SMA)

Calibration of dynamic traffic assignment models with point-to-point traffic surveillance

Vaze, Vikrant (Vikrant Suhas)
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 180 p.
ENG
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Accurate calibration of demand and supply simulators within a Dynamic Traffic Assignment (DTA) system is critical for the provision of consistent travel information and efficient traffic management. Emerging traffic surveillance devices such as Automatic Vehicle Identification (AVI) technology provide a rich source of disaggregate traffic data. This thesis presents a methodology for calibration of demand and supply model parameters using travel time measurements obtained from these emerging traffic sensing technologies. The calibration problem has been formulated in two different frameworks, viz. in a state-space framework and in a stochastic optimization framework. Three different algorithms are used for solving the calibration problem, a gradient approximation based path search method (SPSA), a random search meta-heuristic (GA) and a Monte-Carlo simulation based technique (Particle Filter). The methodology is first tested using a small synthetic study network to illustrate its effectiveness. Later the methodology is applied to a real traffic network in the Lower Westchester County region in New York to demonstrate its scalability.; (cont.) The estimation results are tested using a calibrated Microscopic Traffic Simulator (MITSIMLab). The results are compared to the base case of calibration using only the conventional point sensor data. The results indicate that the utilization of AVI data significantly improves the calibration accuracy.; by Vikrant Vaze.; Thesis (S.M.)--Massachusetts Institute of Technology...

An Improved Framework for Dynamic Origin-Destination (O-D) Matrix Estimation

Chi, Hongbo
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
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This dissertation aims to improve the performance of existing assignment-based dynamic origin-destination (O-D) matrix estimation models to successfully apply Intelligent Transportation Systems (ITS) strategies for the purposes of traffic congestion relief and dynamic traffic assignment (DTA) in transportation network modeling. The methodology framework has two advantages over the existing assignment-based dynamic O-D matrix estimation models. First, it combines an initial O-D estimation model into the estimation process to provide a high confidence level of initial input for the dynamic O-D estimation model, which has the potential to improve the final estimation results and reduce the associated computation time. Second, the proposed methodology framework can automatically convert traffic volume deviation to traffic density deviation in the objective function under congested traffic conditions. Traffic density is a better indicator for traffic demand than traffic volume under congested traffic condition, thus the conversion can contribute to improving the estimation performance. The proposed method indicates a better performance than a typical assignment-based estimation model (Zhou et al., 2003) in several case studies. In the case study for I-95 in Miami-Dade County...

Advanced Methodologies in Dynamic Traffic Assignment Modeling of Managed Lanes

Shabanian, Shaghayegh
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica Formato: application/pdf
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Managed lane strategies are innovative road operation schemes for addressing congestion problems. These strategies operate a lane (lanes) adjacent to a freeway that provides congestion-free trips to eligible users, such as transit or toll-payers. To ensure the successful implementation of managed lanes, the demand on these lanes need to be accurately estimated. Among different approaches for predicting this demand, the four-step demand forecasting process is most common. Managed lane demand is usually estimated at the assignment step. Therefore, the key to reliably estimating the demand is the utilization of effective assignment modeling processes. Managed lanes are particularly effective when the road is functioning at near-capacity. Therefore, capturing variations in demand and network attributes and performance is crucial for their modeling, monitoring and operation. As a result, traditional modeling approaches, such as those used in static traffic assignment of demand forecasting models, fail to correctly predict the managed lane demand and the associated system performance. The present study demonstrates the power of the more advanced modeling approach of dynamic traffic assignment (DTA), as well as the shortcomings of conventional approaches...

Advanced methodologies in dynamic traffic assignment modeling of managed lanes

Shabanian, Shaghayegh
Fonte: FIU Digital Commons Publicador: FIU Digital Commons
Tipo: Artigo de Revista Científica
EN
Relevância na Pesquisa
46.41%
Managed lane strategies are innovative road operation schemes for addressing congestion problems. These strategies operate a lane (lanes) adjacent to a freeway that provides congestion-free trips to eligible users, such as transit or toll-payers. To ensure the successful implementation of managed lanes, the demand on these lanes need to be accurately estimated. Among different approaches for predicting this demand, the four-step demand forecasting process is most common. Managed lane demand is usually estimated at the assignment step. Therefore, the key to reliably estimating the demand is the utilization of effective assignment modeling processes. ^ Managed lanes are particularly effective when the road is functioning at near-capacity. Therefore, capturing variations in demand and network attributes and performance is crucial for their modeling, monitoring and operation. As a result, traditional modeling approaches, such as those used in static traffic assignment of demand forecasting models, fail to correctly predict the managed lane demand and the associated system performance. The present study demonstrates the power of the more advanced modeling approach of dynamic traffic assignment (DTA), as well as the shortcomings of conventional approaches...

Efficient duty cycle MAC protocols for dynamic traffic loads in wireless sensor networks

Sun, Yanjun
Fonte: Universidade Rice Publicador: Universidade Rice
ENG
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46.26%
Idle listening is one of the most significant causes of energy consumption in wireless sensor networks (WSNs), and many protocols have been proposed based on duty cycling to reduce this cost. These protocols, either synchronous or asynchronous, are mainly optimized for light traffic loads. A WSN, however, could often experience bursty and high traffic loads, as may happen for example with broadcast or convergecast traffic. In this thesis, I design and evaluate a new synchronous protocol, DW-MAC (Demand Wakeup MAC), and a new asynchronous protocol, RI-MAC (Receiver Initiated MAC), that are both efficient under dynamic traffic loads, including light or heavy loads. I also design and evaluate ADB (Asynchronous Duty-cycle Broadcasting), a new protocol for efficient multihop broadcasting in WSNs using asynchronous duty cycling. DW-MAC introduces a new low-overhead scheduling algorithm that allows nodes to wake up on demand during the Sleep period of an operational cycle and ensures that data transmissions do not collide at their intended receivers; this demand wakeup adaptively increases effective channel capacity as traffic load increases. RI-MAC, instead, uses receiver-initiated transmissions, in which each transmitter passively waits until its intended receiver wakes up and transmits a beacon frame; this technique minimizes the time a sender and its intended receiver occupy the wireless medium to find a rendezvous time for exchanging data. ADB is integrated with RI-MAC to exploit information only available at this layer; rather than treating the data transmission from a node to all of its neighbors as the basic unit of progress for the multihop broadcast. ADB dynamically optimizes the broadcast at the level of transmission to each individual neighbor of a node as the neighbors asynchronously wakeup...

Métodos matemáticos para la predicción de tráfico

Nogal Macho, María
Fonte: Universidad de Cantabria Publicador: Universidad de Cantabria
Tipo: Tese de Doutorado
ENG
Relevância na Pesquisa
46.44%
RESUMEN: Esta tesis desarrolla los siguientes modelos matemáticos originales: - Un modelo bayesiano conjugado para la reconstrucción y estimación de los flujos de tráfico a partir de la lectura de las matrículas, que permite calcular los diferentes flujos de tráfico, tales como los de rutas, origen-destino, arcos escaneados o arcos aforados. - Un modelo dinámico de recarga, continuo en el tiempo, consistente con la regla FIFO, que evalúa el efecto de la congestión teniendo en cuenta la interacción de los flujos de todas las rutas y su coincidencia en diferentes momentos y lugares. Se supone que el tiempo de recorrido del arco es función no lineal de los volúmenes de tráfico del mismo y, además, se tiene en cuenta el efecto derivado de la congestión en los arcos aguas abajo de la ruta. - Un modelo de tráfico dinámico con demanda estocástica para la predicción de algunas variables de tráfico, tales como los tiempos de recorrido, flujos o densidad de los arcos y su evolución en el tiempo. Todos los modelos propuestos se han ensayado en redes de tráfico reales como son Cuenca y Ciudad Real (España) y el estado de Vermont (EE.UU.), con el fin de analizar sus características, validez de los resultados y los correspondientes requisitos computacionales. Además...

Groupage et protection du trafic dynamique dans les réseaux WDM

Metnani, Ammar
Fonte: Université de Montréal Publicador: Université de Montréal
Tipo: Thèse ou Mémoire numérique / Electronic Thesis or Dissertation
FR
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46.52%
Avec les nouvelles technologies des réseaux optiques, une quantité de données de plus en plus grande peut être transportée par une seule longueur d'onde. Cette quantité peut atteindre jusqu’à 40 gigabits par seconde (Gbps). Les flots de données individuels quant à eux demandent beaucoup moins de bande passante. Le groupage de trafic est une technique qui permet l'utilisation efficace de la bande passante offerte par une longueur d'onde. Elle consiste à assembler plusieurs flots de données de bas débit en une seule entité de données qui peut être transporté sur une longueur d'onde. La technique demultiplexage en longueurs d'onde (Wavelength Division Multiplexing WDM) permet de transporter plusieurs longueurs d'onde sur une même fibre. L'utilisation des deux techniques : WDM et groupage de trafic, permet de transporter une quantité de données de l'ordre de terabits par seconde (Tbps) sur une même fibre optique. La protection du trafic dans les réseaux optiques devient alors une opération très vitale pour ces réseaux, puisqu'une seule panne peut perturber des milliers d'utilisateurs et engendre des pertes importantes jusqu'à plusieurs millions de dollars à l'opérateur et aux utilisateurs du réseau. La technique de protection consiste à réserver une capacité supplémentaire pour acheminer le trafic en cas de panne dans le réseau. Cette thèse porte sur l'étude des techniques de groupage et de protection du trafic en utilisant les p-cycles dans les réseaux optiques dans un contexte de trafic dynamique. La majorité des travaux existants considère un trafic statique où l'état du réseau ainsi que le trafic sont donnés au début et ne changent pas. En plus...

Second-Order Fluid Dynamics Models for Travel Times in Dynamic Transportation Networks

Kachani, Soulaymane; Perakis, Georgia
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 571373 bytes; application/pdf
EN_US
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In recent years, traffic congestion in transportation networks has grown rapidly and has become an acute problem. The impetus for studying this problem has been further strengthened due to the fast growing field of Intelligent Vehicle Highway Systems (IVHS). Therefore, it is critical to investigate and understand its nature and address questions of the type: how are traffic patterns formed? and how can traffic congestion be alleviated? Understanding drivers' travel times is key behind this problem. In this paper, we present macroscopic models for determining analytical forms for travel times. We take a fluid dynamics approach by noticing that traffic macroscopically behaves like a fluid. Our contributions in this work are the following: (i) We propose two second-order non-separable macroscopic models for analytically estimating travel time functions: the Polynomial Travel Time (PTT) Model and the Exponential Travel Time (ETT) Model. These models generalize the models proposed by Kachani and Perakis as they incorporate second-order effects such as reaction of drivers to upstream and downstream congestion as well as second-order link interaction effects. (ii) Based on piecewise linear and piecewise quadratic approximations of the departure flow rates...

A Simulation Method for Calculating the Path Travel Time in Dynamic Transportation Network

Lin, G.C.; Peraire, Jaime; Khoo, Boo Cheong; Perakis, Georgia
Fonte: MIT - Massachusetts Institute of Technology Publicador: MIT - Massachusetts Institute of Technology
Tipo: Artigo de Revista Científica Formato: 198734 bytes; application/pdf
EN_US
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The calculation of path travel times is an essential component for the dynamic traffic assignment and equilibrium problems. This paper presents a simulation method for calculating actual path travel times for the traffic network with dynamic demands. The method is based on a path-based macroscopic simulation model of network traffic dynamics. There is no need to explicitly model intersection delays in this method. Discontinuity in the travel time caused by traffic light control can be captured by this method. It's flexible in terms that the model is not limited to a specific velocity-density relationship. Some numerical results for signalized and unsignalized networks are reported.; Singapore-MIT Alliance (SMA)

Off-line calibration of Dynamic Traffic Assignment models; Off-line calibration of DTA models

Balakrishna, Ramachandran, 1978-
Fonte: Massachusetts Institute of Technology Publicador: Massachusetts Institute of Technology
Tipo: Tese de Doutorado Formato: 212 p.
ENG
Relevância na Pesquisa
46.35%
Advances in Intelligent Transportation Systems (ITS) have resulted in the deployment of surveillance systems that automatically collect and store extensive network-wide traffic data. Dynamic Traffic Assignment (DTA) models have also been developed for a variety of dynamic traffic management applications. Such models are designed to estimate and predict the evolution of congestion through detailed models and algorithms that capture travel demand, network supply and their complex interactions. The availability of rich time-varying traffic data spanning multiple days thus provides the opportunity to calibrate a DTA model's many inputs and parameters, so that its outputs reflect field conditions. The current state of the art of DTA model calibration is a sequential approach, in which supply model calibration (assuming known demand inputs) is followed by demand calibration with fixed supply parameters. In this thesis, we develop an off-line DTA model calibration methodology for the simultaneous estimation of all demand and supply inputs and parameters, using sensor data. We adopt a minimization formulation that can use any general traffic data, and present approaches to solve the complex, non-linear, stochastic optimization problem.; (cont.) Case studies with DynaMIT...

Grooming of Dynamic Traffic in WDM Star and Tree Networks Using Genetic Algorithm

Liu, Kun-hong; Xu, Yong; Huang, De-shuang; Cheng, Min
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 25/10/2006
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The advances in WDM technology lead to the great interest in traffic grooming problems. As traffic often changes from time to time, the problem of grooming dynamic traffic is of great practical value. In this paper, we discuss dynamic grooming of traffic in star and tree networks. A genetic algorithm (GA) based approach is proposed to support arbitrary dynamic traffic patterns, which minimizes the number of ADM's and wavelengths. To evaluate the algorithm, tighter bounds are derived. Computer simulation results show that our algorithm is efficient in reducing both the numbers of ADM's and wavelengths in tree and star networks.; Comment: 15 pages

A Genetic Algorithm Approach to the Grooming of Dynamic Traffic in Tree and Star Networks with Bifurcation

Liu, Kun-hong; Xu, Yong; Huang, De-Shuang
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 27/10/2006
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Traffic grooming is widely employed to reduce the number of ADM's and wavelengths. We consider the problem of grooming of dynamic traffic in WDM tree and star networks in this paper. To achieve better results, we used the bifurcation techniques to the grooming of arbitrary dynamic traffic in a strictly non-blocking manner in networks. Three splitting methods, including Traffic-Cutting, Traffic-Dividing and Synthesized-Splitting were proposed. A genetic algorithm (GA) approach based on these methods was proposed to tackle such grooming problems in tree and star networks. The performance of these algorithms was tested under different conditions in star and tree networks. Computer simulation results showed that our algorithm is efficient in reducing both the numbers of ADM's and wavelengths.; Comment: 16 pages; Guangxi, Guilin, Proceeding of the 10th International Conference on Intelligent Technologies, pp. 524-533

Convexity and Robustness of Dynamic Traffic Assignment for Control of Freeway Networks

Como, Giacomo; Lovisari, Enrico; Savla, Ketan
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 21/09/2015
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We study System Optimum Dynamic Traffic Assignment (SO-DTA) for realistic traffic dynamics controlled by variable speed limits, ramp metering, and routing controls. We consider continuous-time cell-based Dynamic Network Loading models that include as special cases the Cell Transmission Model (CTM) with FIFO rule at the diverge junctions as well as non-FIFO diverge rules. While a straightforward consideration of traffic dynamics and control variables in the SO-DTA is known to lead to a non-convex program, and hence is computationally expensive for real-time applications, we consider SO-DTA formulations in which the total inflow into and the total outflow from the cells are independently constrained to be upper bounded by concave supply and demand functions, respectively, thus preserving convexity. We then design open-loop controllers that guarantee that the optimal solutions under the relaxed constraints are feasible with respect to realistic traffic dynamics. We develop this methodology for three variations of the SO-DTA problem that impose constraints on turning ratios to varying degrees. Using tools from optimal control, we identify specific scenarios in which the optimal solution under the relaxed constraints is readily feasible with respect to the CTM...

On the Continuum Approximation of the On-and-off Signal Control on Dynamic Traffic Networks

Han, Ke; Gayah, Vikash; Piccoli, Benedetto; Friesz, Terry L.; Yao, Tao
Fonte: Universidade Cornell Publicador: Universidade Cornell
Tipo: Artigo de Revista Científica
Publicado em 13/09/2013
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In the modeling of traffic networks, a signalized junction is typically treated using a binary variable to model the on-and-off nature of signal operation. One way of approximating such signal control is through a continuum approach where the on-and-off control variable is replaced by a priority parameter. Advantages of such approximation include elimination of the need for binary variables, lower time resolution requirements, and more flexibility and robustness in a decision environment. It also resolves the issue of discontinuous travel time functions arising from the context of dynamic traffic assignment. Despite these advantages in application, it is not clear from a theoretical point of view how accurate is such continuum approach; i.e., to what extent is this a valid approximation for the on-and-off case. The goal of this paper is to answer these basic research questions and provide further guidance for the application of such continuum signal model. In particular, by employing the Lighthill-Whitham-Richards model (Lighthill and Whitham, 1955; Richards, 1956) on a traffic network, we investigate the convergence of the on-and-off signal model to the continuum model in regimes of diminishing signal cycles. We also provide numerical analysis on the continuum approximation error when the signal cycle is not infinitesimal. As we explain...