Sharif Digital Repository

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... 

The road authorities of a city have the responsibility of constantly assessing how well their city performs when traffic conditions are taken into account. In many metropolises around the world, if not taken preventive measures, there will be observed a density above the network capacity and a noticeable decrease in the level of service, especially in the morning and evening peak hours. Also, the dynamic congestion pricing of certain areas based on the traffic condition has always been considered significant by urban planning officials. Since this is not possible except by constantly assessing the current traffic state, a variety of methods have been used to predict the future traffic... 

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... 

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... 

Encouraging passengers in order to use public transportation facilities is one of the goals of transportation planners. The most effective way to increase the market share of public transportation is enhancing its Level of Service via faster and more comfortable transportation in comparison with private vehicles. Exploitation of rapid transportation lines (Subway, BRT, and etc.) is justifiable in corridors in which the demand exceeds a minimum value. While in most of metropolitans such demand may not be present inadvertently in any of corridors, generating the needed demand and increasing the accessibility to public transportation is possible using feeder lines like feeder buses. In fact,... 

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... 

This thesis extends a probabilistic framework for evaluating the seismic resilience of communities by modeling the transportation system. The framework that is being extended is under continuous development at the Center for Infrastructure Sustainability and Resilience Research (INSURER) at Sharif University of Technology quantifies community resilience by integrating hazard models, risk models, and recovery models within an agent-based simulation. In this framework, the transportation system is modeled by developing a library of probabilistic models to predict the occurrence and intensity of earthquake hazard, damage and capacity of network components, network travel demand, and economic,... 

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... 

Congestion is the inseparable part of everyday life in large transportation networks. Expansion of road networks especially in downtown area is next to impossible and it is resulting multiplicative congestion problems. Congestion imposes private and public costs. Therefore, restricting policies on road use through cordon-based or area-based pricing is proposed to reduce the negative impacts of traffic, travel demand management and optimal use of transportation systems. This would produce better resource allocation through transportation network optimization. Implementation of congestion pricing policies induces short-term and long-term effects. In this thesis, it is attempted to determine... 

Inappropriate use of the transportation networks is one of the causes of network congestion. Toll pricing is one of the traffic management tools to mitigate delay and congestion by guiding traffic flow to proper time and route. Efficient use of network facilities is one of transportation planners’ goal and highways are one of the most important facilities in a transportation network. In this study, we investigate the highway toll pricing problem in order to reduce total travel time for the users. We introduce four different strategies to collect toll from highway users. Direct solution methods for large networks faced with the problem of solving time. In this regard, some heuristics methods... 

The toll pricing problem has been investigated in the literature for the cases of link, cordon, and facility (bridge, tunnel and etc.) pricing. Taking advantages of new technologies, nowadays it is possible to track the path of individual vehicles and collect the tolls by means of electronic devices. In this regard, we concerned the problem of path pricing. In this thesis, a variety of models for path pricing is proposed, the models are solved for the Hearn network and the results are compared to the results of link pricing models. In addition to the models, one exact solution method and two heuristic methods are proposed for the model of path pricing with the minimum total toll.... 

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.... 

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... 

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... 

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... 

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... 

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... 

Long-term effects of natural disasters, like earthquakes, in many cases have been reported high on transportation networks. Disruption in this lifeline network's performance imposes high social and economic costs upon the society. Undoubtedly, retrofitting the structures of all network links (or constructing new links) are practically impossible and economically infeasible. One solution to this problem is finding a method for determining the network's important links, and retrofitting their structures. Based on this concept, an optimization problem of network performance improvement under these stochastic events is introduced. In this problem, a link importance index for network links is... 

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...