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dynamical-traffic-assignment
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Correction of Time-Dependent Origin-Destination Demand in Dynamic Traffic Assignment
, M.Sc. Thesis Sharif University of Technology ; Zakaei Ashtiani, Hedayat (Supervisor)
Abstract
Time-dependent origin-destination demand is a key input in dynamic traffic assignment in advanced traffic management systems, and the result of dynamic traffic assignment is dependent on the accuracy of this information. One method to achieve time dependent demand matrices is using a primary demand matrix and volume traffic counts in some links of network. In this thesis a bi-level model is used to correct the demand matrix and the extended gradient method is suggested to solve the problem. The extended gradient is an iterative method that in each iteration, corrects the demand matrix in a way that the estimated traffic flow be close to the observed traffic flow. Execution of this method in...
Estimating time-dependent origin-destination demand from traffic counts: Extended gradient method
, Article Transportation Letters ; Volume 7, Issue 4 , 2015 , Pages 210-218 ; 19427867 (ISSN) ; Nazemi, M ; Seyedabrishami, S ; Sharif University of Technology
Maney Publishing
2015
Abstract
Time-dependent origin-destination (TDOD) demand is a key input of dynamic traffic assignment (DTA) in advanced traffic management systems. Model reliability is highly dependent on the accuracy of this information. One method to achieve TDOD demand matrices is to use a primary demand matrix and traffic volume counts in some links of a network. This paper proposes a bi-level model to correct the TDOD demand matrix. The extended gradient method (EGM) - an iterative method that minimizes the discrepancy between the counted and estimated traffic volumes - is a suggested means to solve this problem. The methodology is first tested on a small synthetic network to verify its performance. Then, it is...
Applying Signal Coordination in Dynamic Traffic Assignment
, M.Sc. Thesis Sharif University of Technology ; Zokaei Aashtiani, Hedayat (Supervisor)
Abstract
Signal Coordination is one of the appropriate methods for delay reduction in intersections. Static Traffic Assignment is unable to reflect the impacts of Signal Coordination in a network. One proper way to overcome this difficulty is to use Dynamic Traffic Assignment (DTA) that can model complex properties of traffic flow. This thesis presents a method to apply Signal Coordination in Cell Transmission Model. Neguin network is tested for different intersection's green start times. The results show that Signal Coordination has great influence on total travel time and route choice in this network. Finally, the results have been checked with AIMSUN NG, a microsimulator software.
A Heuristic Method for Coordination of Signalized Intersection
, M.Sc. Thesis Sharif University of Technology ; Zokaei Ashtiani, Hedayat (Supervisor)
Abstract
Signal coordination is one of the strategies to decrease the delay times in transportation networks. The application of dynamic traffic assignment has been made possible the modeling of flow loading in network links, and queue formation and dissipation in signalized intersections. In this thesis, signal offset set which produce the minimum total travel time in a network is determined, using a cell-based dynamic traffic assignment which is based on the cell transmission model. Genetic algorithm has been implemented to reach the suboptimal offset set. The application of the algorithm on a small test network shows that it can reach to an offset set with 1% error to the optimal offset set, by...
Urban Transportation Network Design in Chaotic Conditions and Uncertainty in Travel Demand
, M.Sc. Thesis Sharif University of Technology ; Pourzahedi, Hossein (Supervisor)
Abstract
Transportation systems are dynamic and complex systems due to the interaction between human and non-human factors. In certain circumstances, the dynamics of traffic flow causes the transportation system fail to reach equilibrium and chaos will occur. In such cases, travel times vary daily and travel time reliability decreases. Moreover, these systems are continuously exposed to incidents that cause a high degree of uncertainty. So, it is necessary to enter such dynamics and uncertainty in the decision making models, such as network design. In this study a bilevel network design problem is defined with chaos and uncertainty taken into account. At the higher level problem, the optimization...
Network Design to Alleviate Chaos in the Transportation Network Flows: Cases of Deterministic and Uncertain Supply
, M.Sc. Thesis Sharif University of Technology ; Pourzahedi, Hossein (Supervisor)
Abstract
Transportation networks are considered as complex systems, and in many cases they behave in such an irregular and unexpected manner. Such complexities cause problems in studying the behavior of these systems. An example of such complexities is chaos in the network flows. On the other hand, the behavior of these networks is highly affected by the incidents like accidents and bad weather. Such events affect the level of service and travel time reliability of the networks. In this research, a dynamical approach to traffic assignment has been chosen to model chaos and uncertainties in the network. By using this approach for modeling flow evolution, edge of chaos and uncertainty in supply and...
Network Design Problem to Prevent Chaotic Flow
, M.Sc. Thesis Sharif University of Technology ; Pourzahedi, Hossein (Supervisor)
Abstract
Two significant features of a transportation network, uncertainty and complexity, might cause some irregular behaviors. One example of such behaviors is chaotic flow in which the transportation system fails to reach equilibrium and people experience different daily travel times. These uncertainties are not controllable in any transportation system and, if not taken into consideration, will result to low levels of service and poor reliability. In this study, an evolutionary traffic assignmet model is used to illustrate when the network reaches bifurcation and chaos. Later, the effects of uncertainty in the parameters of supply and demand is tested on the evolutionary traffic assignment model....
The treatment of uncertainty in the dynamic origin–destination estimation problem using a fuzzy approach
, Article Transportation Planning and Technology ; Volume 38, Issue 7 , 2015 , Pages 795-815 ; 03081060 (ISSN) ; Shafahi, Y ; Sharif University of Technology
Routledge
2015
Abstract
Regardless of existing types of transportation and traffic model and their applications, the essential input to these models is travel demand, which is usually described using origin–destination (OD) matrices. Due to the high cost and time required for the direct development of such matrices, they are sometimes estimated indirectly from traffic measurements recorded from the transportation network. Based on an assumed demand profile, OD estimation problems can be categorized into static or dynamic groups. Dynamic OD demand provides valuable information on the within-day fluctuation of traffic, which can be employed to analyse congestion dissipation. In addition, OD estimates are essential...
Parallel Implemetaion of Dynamic Traffic Assignment
, M.Sc. Thesis Sharif University of Technology ; Shafahi, Yousef (Supervisor)
Abstract
In this research, a Simulation-based Dynamic Traffic Assignment model based on parallel Processing is proposed. Dynamic Traffic Assignment has two key sub problems: Route choice modeling and Dynamic network loading. In route choice problem, a Type-II fuzzy system is proposed to model the complexities and ambiguities, which exist in the behavior of network users. The model can consider behaviors of network users in the forms of route choosing and route changing. In dynamic network loading problem, a Cellular Automata model is proposed as a microscopic simulator. Finally, In order to speed up the model and to use it in real time problems, the proposed Dynamic Traffic Assignment algorithm is...
Predictive Cordon Pricing to Reduce Air Pollution
, Ph.D. Dissertation Sharif University of Technology ; Poorzahedy, Hossain (Supervisor) ; Lindsey, Robin (Co-Supervisor)
Abstract
Traffic is a major contributor to emissions in many large cities with severe air pollution. Experience in London, Milan, and Stockholm shows that charging for the use of roads can be effective in reducing emissions, as well as congestion. This study examines the use of predictive cordon tolls based on weather forecasts to reduce ambient air pollution and congestion. Travelers choose their destinations inside or outside the cordon, and whether to drive or take public transport. Passenger vehicles are divided into three classes according to their emission characteristics, and higher tolls are imposed on more polluting vehicles. The Box model of emission dispersion is used to predict air...