Sharif Digital Repository

Network design problem has been, and is, an important problem in transportation. Network design based on different objectives affects network's performance in different dimensions, so it is crucial to define a good objective for the network design problem that improves the network's performance in more than one aspect. The purpose of this study is to obtain the differences between the two network design problems, one based on resiliency, and the other based on consumer surplus.Network design problem based on consumer surplus minimizes the total travel time for the users in the network. Network design problem based on resiliency is defined as: (1) before the incident, (2) after the incident... 

Nowadays more than half of the world’s population lived in urban areas. That proportion is set to rise to 67% by 2050. This will cause urban mobility with serious problems. The concept of Urban Air Mobility (UAM) is proposed to avoid the problem to become a catastrophy. Due to environmental issues and also high operating costs, using copters as an air-taxi was not justifiable. As the technology in e-VTOL flourished, the desire of using of these vehicles in such a transportation system was increased. In this paper, besides previous investigations, the e-VTOL’s performance parameters’ influence on the characteristic of a civil air-taxi network is under investigation. In addition, this paper... 

Natural hazards such as earthquake take many lives each year and cause significant damages to infrastructures such as transportation networks. Whether after occurrence of a natural disaster like storm in order to evacuate, or after an abrupt event such as earthquake in order to provide emergency measures, a transportation network should maintain its functionality and performance in an acceptable degree and should recover in an effectively short period of time. In this study, the link or the set of links which their removal causes significant damage to the transportation network are identified. A specific index (N-Q index) has been used to describe the performance of the network. In addition,... 

Due to the importance of hazardous materials (hazmat) transportation, this problem should be programmed and solved appropriately. Hazardous materials are substances that may endanger the health of humans, animals and the environment. One of the most important parameters in hazmat transportation problem is risk, since other routing researches don’t involve risk as an influencing parameter. In the scientific literature of the transport of hazardous materials, the risk is defined by the calculation of the probability and severity of damage to the endangered recipient through unwanted warnings from hazardous substances. In the model of this research, the accident rate is considered as the... 

This research deals with pricing private automobiles entering a congested area in urban CBD to reduce auto-related air pollution. There are two factors affecting the pollution level: car volumes, and the weather condition. A Markov decision process is employed to find the optimal tolls and determine the prices for different states of the system, under several weather conditions. The demand for travel is elastic. It is assumed that users change modes in the short run. In longer terms, the part of the demand with shopping, recreation, or similar flexible trip purposes change the respective demand levels according to the price level. The study attempts to estimate elastic demand functions for... 

The present study investigates dynamic pricing in case of urban transportation operators competing on an identical network. Game theory has been adopted as an approach to the modeling and solutions.Game theory is a mathematical theory widely applied in competitive situations.The proposed model takes the players’ interdependency problems into account to predict their decisions as well as the displacement on the network about equilibrium point. The problem is modeled in no-cooperation state using the dynamic Nash equilibrium; Gauss-Seidel algorithm is used for the solutions considering the discontinuity of the decision space. A comprehensive sensitivity analysis has also been conducted on the... 

Transportation problem is one of the most important parts in supply chain management and it offers great potential to reduce costs and improve service quality. So many research efforts, are considering the optimization of the transportation systems and its related aspects. In this thesis, a transportation system according to a real case study, with the aim of minimizing total cost is considered. It is assumed a fleet of vehicles with limited capacity and different fixed and variable costs are shipping different products from a manufacturing plant to their associated nationwide distribution storages. Certain number of storages or depots with deterministic demand is available and each has a... 

This study aims to solve weekly Flight Frequency Determination and Aircraft Maintenance Routing Problem (AMRP) simultaneously. The objective function here is to maximize the total net profit of an assumptive airline with predetermined airfare and origin-destination market demand. All the needed constraints regarding AMRP is added to the modified version of original model which proposed by Ghafoori in 2011. On the other hand, while this kind of model is based on travelling salesman problem, the occurrence of sub-tours is inevitable. Thus, the model will be, secondly, restricted with more constraints which help eliminate infeasible solutions. The proposed model, then, is tested for three... 

Transportation Network Companies (TNC) like Snap and Tap30 are ride sharing platforms that connect drivers and passengers in real time using simple mobile phone applications. The most interesting feature of these platforms is that they do not hire drivers and allow them to choose when and where to offer a ride. Dynamic and fluctuating supply and demand, the necessity to forecast the changes, implementing them in ride pricing and driver-passenger assessment are considered as important challenges for such systems. In this research, first, we want to analyze the spatial structure of TNCs and then forecast network changes more precisely. The method used for forecasting is LASSO which is a... 

In this study, given the increasing challenges urban and intercity transportation face in the modern world, including population growth, urban development, and environmental concerns, an innovative approach to optimize the use of car-sharing vehicles is presented. The research aims to develop a multi-objective mathematical programming model for the optimal allocation of car-sharing vehicles, considering key factors such as transportation costs, travel time, and environmental pollution. This seeks to reduce costs, increase efficiency, shorten travel times, and contribute to environmental sustainability. Initially, a thorough literature review was conducted to provide a comprehensive... 

A city is a complex system which consists of many interactive sub-systems. It is affected by diverse factors including governmental land policies, population growth, market behavior and transportation infrastructure. Traffic congestion is one of the most critical challenges of transport infrastructure which became everyday occurrence in the last decades. The traffic planners and traffic engineers have faced real obstacles due to the growth of motorization and the resulted external consequences. Furthermore the capacity of the traffic networks saturates during rush hours. Generally, network transport performance can be improved in two ways, optimizing network structure (Hard Strategy) or... 

Natural disasters, earthquakes in particular, claim many human lives and damage major lifelines such as transportation networks. Transportation networks play an important role in various stages of response to disasters, such as evacuation, search, rescue and reconstruction missions. Hence, special attention must be paid to transportation networks in any disaster management system. Hence, in order to reduce the impacts of earthquakes on denser cities and metropolitan areas, analysis of the resiliency and vulnerability of critical infrastructures such as transportation network, can be used as an effective strategy.The resiliency and vulnerability of transportation network have attract a lot... 

Travel time estimation is a central issue in the urban transportation industry and is the basis of many analyses and services in businesses related to this area. In the past few years, various statistical approaches have been devised to solve this problem. The purpose of this dissertation is to review existing methods by focusing on segment-based approaches for urban travel time estimation. A big challenge is the small amount of data in hand compared to the size of the urban network. Exploring historical data and extracting correlation between urban network segments leads to modeling the urban traffic condition and travel time estimation in one specific time interval of the day  

Pricing problem in transportation networks focuses on determining tolls that cause travellers, motivated only by their travel costs, to choose routes that would collectively benefit all travellers and results in optimal utilization of transport network resources.This thesis addresses the toll pricing problem in which the objective is to minimize the number of required toll facilities in a transportation network. Minimum tollbooth problem (MINTB) has binary variables and is very difficult to solve. In this thesis a new heuristic approach has been presented for solving MINTB problem. The results show that, this approach is much faster than the existing algorithms and is able to solve real size... 

Nowadays, with the advent of Autonomous Vehicles(AV), Researchers in different areas focused more on this type of vehicle. Research shows that autonomous vehicles are faster and more precise than Human-driven vehicles(HDV). So if all the users in a road use autonomous Vehicles, the road’s capacity increases; this Thesis develops a mathematical approach for designing AV exclusive lanes for a time horizon in which there are two types of AVs and HDVs on the road. Considering each type of vehicle’s relative performance for an OD pair in the given year, the demand for that OD pair for the next year calculates with a diffusion model. Designing AV exclusive lanes problem is formulated in a bi-level... 

Natural phenomena, such as earthquakes, floods, and hurricanes, have been, and will be, one major source of mankind disastrous problems. Mankindinterventions to relieve this heavy pressure on humanity have been divided into four categories: mitigation, preparedness, response, and recovery. This study is in the response phase, and aims to find an optimal network to help people in the devastated part of a city, hit by a major earthquake. Such earthquakes demolish buildings over the people inside, causing them fatal harm and serious injuries. At the same time, they ruin the city infrastructures (life lines), including transportation networks, preventing flow of relief supply to reach to the... 

Resiliency is, now, recognized as a vital characteristics of every urban transportation network. This is so, because transportation network is considered as a life-line in disastrous events, such as major earthquakes. In this respect, design of networks may be considered (1) before the incident, (2) after the incident for 72 hours, and (3) from this 72 hours on. From the point of view of (1), design of the network may be considered as strengthening important links under budget constraints to withstand the design incident, in order to be able to function properly (to help the affected people, to evacuate the populated area, etc.).Design of network based on the point of view of (2), the one... 

Toll Pricing as a means to relieve traffic congestion has received significant attention by transportation planners recently. Inappropriate use of transportation networks is one of the major reasons that cause congestion in networks. Toll Pricing is a method of traffic management which guides the traffic flow to proper time and path in order to reduce the total delay in networks. This thesis investigates a method for solving Minimum Toll Revenue problem in real and large scale transportation networks. The objective of this problem is to find tolls that simultaneously cause users to use the transportation network effectively and minimize the total toll revenues that must be collected.... 

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... 

Hub and Spoke networks come into play when considering direct link between all origins and destinations is either impossible or expensive in a transportation system. In this kind of problems, some nodes are chosen as hub from all origin and destination nodes to collect flows and then distribute them. Implementing hub network leads to minimizing transportation cost, sorting flows and conveying them in economies of scale. Otherwise, shipping flows directly may cause decreasing the travelling distance and the delivery time consequently. In this dissertation, combination of hub network and direct shipment is investigated. To obtain the optimal hub locations and direct links between non-hub nodes...