Search for: urban-networks
A heuristic methodology to tackle the Braess Paradox detecting problem tailored for real road networks, Article Transportmetrica A: Transport Science ; Vol. 10, issue. 5 , 2014 , p. 437-456 ; Ceder, A ; Tavana, M ; Bozic, C ; Sharif University of Technology
Adding a new road to help traffic flow in a congested urban network may at first appear to be a good idea. The Braess Paradox (BP) says, adding new capacity may actually worsen traffic flow. BP does not only call for extra vigilance in expanding a network, it also highlights a question: Does BP exist in existing networks? Literature reveals that BP is rife in real world. This study proposes a methodology to find a set of roads in a real network, whose closure improve traffic flow. It is called the Braess Paradox Detection (BPD) problem. Literature proves that the BPD problem is highly intractable especially in real networks and no efficient method has been introduced. We developed a...
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
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...
M.Sc. Thesis Sharif University of Technology ; Nassiri, Habibollah
Urban transportation infrastructure due to the emergency forces' access during and after the earthquake is one of the most important arteries in the face of crisis. The resilience of this infrastructure is a crucial factor that should control before an event, such as an earthquake, to prioritize segments for improving their conditions and prevent system disruption. In this research, a model presents for evaluating urban roads' resilience based on four characteristics of robustness, redundancy, resourcefulness, and rapidity. The fuzzy inference is employed to construct the model. Due to the expert opinion dependence of these models, the AHP questionnaire is used to train the model. In this...
Article IEEE Transactions on Power Systems ; Volume 26, Issue 4 , 2011 , Pages 2293-2301 ; 08858950 (ISSN) ; Ehsan, M ; Caire, R ; Hadjsaid, N ; Sharif University of Technology
In deregulated power systems, the distribution network operator (DNO) is not responsible for investment in distributed generation (DG) units, and they are just concerned about the best architecture ensuring a good service quality to their customers. The investment and operating decisions related to DG units are then taken by entities other than DNO which are exposed to uncertainty. The DNO should be able to evaluate the technical effects of these uncertain decisions. This paper proposes a fuzzy evaluation tool for analyzing the effect of investment and operation of DG units on active losses and the ability of distribution network in load supply at presence of uncertainties. The considered...
Article Scientia Iranica ; Volume 17, Issue 4 A , August , 2010 , Pages 285-296 ; 10263098 (ISSN) ; Shafahi, Y ; Seyedabrishami, S. E ; Sharif University of Technology
This paper proposes a method to solve shortest path problems in route choice processes when each link's travel time is a fuzzy number, called the Perceived Travel Time (PTT). The PTT is a subjective travel time perceived by a driver. The algorithm solves the fuzzy shortest path problem (FSPA) for drivers in the presence of uncertainty regarding route travel time. For congested networks, the method is able to find the shortest path in terms of perceived travel time and degree of saturation (congestion) along routes at the same time. The FSPA can be used to support the fuzzification of traffic assignment algorithms. The applicability of the resulting FSPA for the traffic assignment was tested...