Sharif Digital Repository

The thesis is about transit network scheduling problem and aims to minimize waiting time at transfer stations. The problem is formulated as a mixed integer programing model that gives departure times of vehicles in lines so that passengers can transfer between lines at transfer stations with minimum waiting time. The model is expanded to another model by considering an extra stoping time of vehicles at transfer stations as a new variable set. By calculationg the optimal value for these variables, transfers could be done in a better condition. The sizes of the models are small enough that the models can be solved for small and medium size networks using regular MIP solvers. Moreover, a... 

Railways managers have strong economic incentive to minimize the track maintenance costs, while maintaining safety standards and providing adequate service levels to train operators. . The aim of this study is providing a method for repair and maintenance management of Iranian Railways and improving previous investigations.This study consists of three parts. First, providing a new definition for the rail's status based on fuzzy theory. Second, a cumulative damage model based on a Fuzzy Markov process is applied to model the deterioration of the track. For this reason, tracks are categorized into six classes, so that those tracks with similar traffic loads and geographical location are... 

In this research a model is proposed which determines flight frequency and aircraft routing for an airline network. It is supposed that origin-destination demand, costs, number of aircrafts in the fleet and their capacity, aircraft maximum daily utilization hours and origin-destination fares are given. The model attempts to maximize airline profit and determines flight frequencies, number of passengers carried between two cities and number of passengers who travel with an indirect flight, considering fleet constraints and an operational aircraft routing.The model is tested with a hypothetical numerical example. The results indicate that the model uses maximum aircraft capacity and daily... 

Optimum highway alignment problem is among the most substantial but large and complicated topics in transportation area. Infinite number of feasible solutions, numerous local optima and the constrained feature of the problem, associated with complex and mainly non-linear constrains, has put an extra effort into the problem-solving process. Moreover, the problem has a sensitive objective function to input variables. Due to the nature of the problem, conventional methods fail to find any exact solution, and so, using heuristic methods during the solving procedure is inevitable. Large-scale, complexity and sensitivity of the problem leads to a solution which is time-consuming and... 

Due to large range searches (there are various alignments between two points) as well as the complex and non-linear cost functions and a variety of geometric constraints, the problem of optimal railway alignment is known as a difficult problem. For this reason, choosing an alignment between two points is usually done based on a limited number of alignments put forward by experts. In recent years, the study of the railway alignment optimization raised again due to the importance of optimization and introduction of various algorithms and their progress in solving various problems. It is expected that applying metaheuristic optimization algorithms, such as methods based on Swarm intelligence... 

Regardless of the traffic model and its application, an essential input of transportation models is the amount of demand which is usually described using Origin-Destination (OD) matrices. Due to high costs and time of direct development of such matrices, they are estimated indirectly from traffic measurements recorded from the network. Dynamic Origin-Destination demand provides valuable information on within-day fluctuation of traffic demand which could be used in analyzing congestion dissipation. In addition, they are essential inputs of dynamic traffic assignment (DTA) models. The current study presents a fuzzy approach to dynamic OD estimation problem. The problem is designed as a two... 

Traffic assignment is one of the key steps in transportation planning. In this stage, link flows are obtained based on estimated O-D demand in previous steps. The first Wardrop rule is the base for all of proposed traffic assignment models. In these models, number of assumptions has been relaxed to make it more realistic. Stochastic traffic assignment and fuzzy rule are two different approaches to capture the realistic picture of route choice behavior of travelers. In this thesis, we utilize the stochastic distributions to model the fuzzy perception of travelers from link experienced travel time. With using utility theory, fuzzy utility estimation method is proposed as an approach to... 

Railway managers have strong economic incentive to minimize the cost of track maintenance in order to conserve safety standards and provide adequate service levels for train operators. The main object of this study is to provide a method for railway repairing and maintaining management and improve previous researchs.
In this study, a cumulative damage model based upon a nonhomogeneous Markov process is developed to model track deterioration. The maintenance of deteriorating facilities can be a great challenge because the process of deteriorating has random features for some facilities.
The genetic algorithm is used to find the optimal repair for each possible track state in the... 

Travel time is the most significant element in choosing among different modes of transportation. In order to increase the public transportation’s utility we need to utilize some methods to reduce public transportation travel time and passenger delay. Bus system, as one of the major types of public transportation, is mainly influenced by the traffic flow more than other types of public transportation. In order to increase the bus system’s reliability we need to utilize a controlling system so that we could increase its movement discipline and reduce line’s disruption. In this research we proposed an optimization model based on bus holding strategy and the real-time data from the route. This... 

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... 

Accurate prediction of pavement performance is essential to a pavement infrastructure management system. Selection of the prediction model is based on the extent of available data, assumptions used in performance modeling, ease of use and management purposes. Therefore, two methods were proposed in this thesis based on the assumptions of availability and unavailibility of accurate data. The first method presents a two-stage model to classify and accurately predict the performance of a pavement infrastructure system. Sections with similar characteristics are classified into groups using a support vector classifier (SVC). Then, a recurrent neural network (RNN) is utilized to predict... 

Discrete Network Design (DND) is a classical combinatorial problem in transportation planning. According to its exponential nature, the problem has a costly exact solution. In recent decades, however, the advent of parallel computing facilities motivated researchers to apply exact solutions on many combinatorial problems. As a result, parallel Branch-and-Bound (B&B) algorithms emerged as robust methods to address combinatorial problems. This dissertation will investigate the parallel behavior of B&B algorithms in DND through some case studies. Parallelization results suggest that parallel B&B algorithms can achieve linear speed-ups in DND for a large number of processors  

One of the fundamental constraints that should have been in mind in flight scheduling is aircraft maintenance scheduling. Based on the accepted rules, regulations and flight safety, in a given period of time or after definite number of flight hours each aircraft should be sent to maintenance site. This influences the flight schedule. This research provides a comprehensive model for the flight scheduling. Given the flight schedule, number of the flights and aircrafts, maintenance center's capacity and other parameters such as each check's time, allowable flight days and allowable flight hours this model could determine each season's flight schedule and solve the aircraft routing problem.... 

Airlines spend considerable time, effort and financial resources on planning. It is essential to create a competitive timetable and construct a fleet and a crew schedule that utilizes these resources to maximum. Unfortunately, it is all too common that an airline is faced with the necessity of reconstructing their schedule due to some unforeseen event such as an aircraft breakdown or unsuitable weather condition. Rescheduling flight in such conditions is inevitable. In this article, first, a mathematical model is presented to minimize the expense caused by aircraft breakdown, flight delay and airport closure with considering crew constraints. Cancellation, delay, aircraft swaps and replacing... 

Decreasing travel time is one of the main goals of passengers in urban areas for which transportation operators use various policies. Among these policies, expanding public transportation facilities is one of the urban planner major purposes. Considering the fact that making these facilities needs great investment, optimize use of the current facilities is valuable. Waiting time in transit station has influence on increasing passengers’ travel time and inconsistency, so coordination between different transit lines is necessary. In this thesis, creating coordination among different transit lines in a transit network by the use of integer programming is studied in the form of two models. In... 

A basic highway design problem is to find the most economical alignment connecting two given end points based on topography, soil conditions, socioeconomic factors and environmental impacts, while satisfying a set of design and operational constraints. The cost function complexity and numerous limitations such as highway design criteria have made this problem a NP-hard one. In this study, a swarm based searching algorithm has been applied to a three dimensional highway alignment optimization model. The spatial data has been exploited from a GIS databases using a heuristic swift approach. In addition, the majority of cost items that depend on highway design have been extended in a practical... 

Knowledge about travel demand patterns is an important requirement for strategic planning and management of urban transportation networks. Use of theoretical trip distribution models such as growth, gravity or intervening opportunities, estimation with the help of questionnaire surveys and development of volume- based O-D estimation methods have been major fields of scientific efforts in recent years.Rapid changes in land use and transportation networks especially in developing countries has raised the importance level of knowledge about changes in travel demand.Traditional approaches are costly, time consuming and suffer from inaccuracies, so,... 

One of the most important required data in order to consult transportation studies is the amount of trip demand between different zones in the study region. Trip demand is usually presented in form of a table. Due to dependence of the demand on time, it gets classified in two categories: Static and Time dependent. In Time dependent problems, which the scope of this research is, trip demand is affected by network condition and the amount of traffic supply in short periods of time, e.g. 15 minutes. Using Traffic count and prior trip demand table in order to estimate the time dependent Trip demand is among the newest methods of travel demand estimation. In this research despite of older studies... 

Regardless of the traffic model and its application, an essential input of transportation models is the amount of demand which is usually described using Origin-Destination (O-D) matrix. Many reaserchers have developed different O-D matrix estimation methods using traffic counts, which allow simple data collection as opposed to the costly traditional direct estimation methods based on home and roadside interview. However, Link data is not sufficient to obtain an unique answer. This reaserch tries to estimate O-D matrix by using Automated Vehicle Identification(AVI) data. The research formulates the problem of the estimating O-D matrix as a bi-level problem. The upper level consists of...