Sharif Digital Repository

This paper is an endeavor to picture excessive population threats to the resiliency of a large metropolitan area. By employing an existing evolutionary model of traffic flow on a small expository network, we show how chaotic situations occur at certain demand and supply parameter values and try to address the questions: How may one determine city population capacity for its transportation network, what happens if the city passes this limit, or how may one return the city to a stable situation when it runs into unstable or chaotic situations. Under certain assumptions, the paper designs a simulation experiment to revisit the phenomenon discovered by Greenshields in 1934, but for a... 

Day-to-day variation in the travel times of congested urban transportation networks is a frustrating phenomenon to the users of these networks. These users look pessimistically at the path travel times, and learn to spend additional time to safeguard against serious penalties that await late arrivals at the destinations. These additional expenses are charges similar to the tolls in system equilibrium flow problem, but may not be collected. With this conjecture, the user equilibrium (UE) formulation of congested network flow problem would lack some necessary factors in addressing appropriate path choices. This study, following a previous work proposing pessimistic UE (PUE) flow, aims to show... 

Day-to-day variation in the travel times of congested urban transportation networks is a frustrating phenomenon to the users of these networks. These users look pessimistically at the path travel times, and learn to spend additional time to safeguard against serious penalties that await late arrivals at the destinations. These additional expenses are charges similar to the tolls in system equilibrium flow problem, but may not be collected. With this conjecture, the user equilibrium (UE) formulation of congested network flow problem would lack some necessary factors in addressing appropriate path choices. This study, following a previous work proposing pessimistic UE (PUE) flow, aims to show... 

Urban and transportation planners have put a special focus on students' health and fitness in the past decade, however they struggle to find effective policies to promote walking and biking for school trips. Commuting to school is an opportunity to embed a regular physical activity in students' daily routines and prevent many health issues that are stimulated by physical inactivity during childhood. A three level nested logit model is introduced to explain the motives behind school trip modal selection. Four choice situations, namely walking, driving, school busing, and taking public transit are considered. This study, particularly, underscored the significance of model misspecification in... 

Analysis of multi dimensional interactions of flow of energy in passenger vehicle is a complex task that necessitates development and utilization of analytical tools. Development of analytical tools with high complexity is usually based on conclusions of many concepts and theories from different scientific disciplines. In this approach, Passenger vehicle is supposed to be organized in the form of a firm and appears in the market that oriented towards establishing an effective energy supply system which may be identified as delivering the product (person kilometer or tone kilometer) with minimum operation costs. To this end, an optimization model named power software founded on theory of firm... 

Transportation has significant and long lasting economical, social and environmental impacts, and so is an important dimension of urban sustainability. Some attempts have been made to develop sustainable transport indicators, STI. A few studies actually apply STI to compare sustainability among various world cities. In this paper various world cities ranked in terms of urban sustainable transport composite index. The study database is created from UITP databank: "Millennium cities database for sustainable mobility" or MCDST. Firstly sustainable transportation indicators were selected by reviewing past researches. Some indicators are edited or redefined. Consequently 9 STI were developed, 3... 

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... 

Urban transportation is one of the main sources of air pollution in mega cities, and urban job related trips can effectively influence the state of air quality. Tehran, the capital of Iran, with a population of 7.3 million, was selected for this study. The present model is designed to investigate the effect on traffic of the business working hours of different occupations and, as a result, on the status of air pollution. Daily job, non-job and recreational trips using the present vehicle fleet is a major factor affecting air pollution in Tehran. In the context of the present study, the necessary information was utilized to define some relations between job trips and pollutant emissions. The... 

This paper applies the genetic-fuzzy and neuro-fuzzy systems to analyze a disaggregate mode choice problem for work trips. These two artificial intelligence methods have been widely used in many complex engineering problems recently. Some key points in developing genetic-fuzzy and neuro-fuzzy systems to analyze the mode choice problem for a large city are explained. Shiraz urban trips database is applied to prepare the data needed for the models. Results show that the developed models have good ability to estimate the existing situation and also to present reliable predictions for the future conditions of an urban transportation system  

Research projects in urban transportation systems require proper simulation softwares. Such softwares are the basic requirements of any kind of study in electrical transportation systems. Due to high energy consumption of these systems, studies for its optimization are challenging and necessary. In this paper an optimized timetable of trains? movement is proposed in order to completely utilize the regenerative energy of trains? braking in stations. A sample subway system is simulated and Genetic algorithm is used as an optimization method. The effect of headway and reserve times on the amount of energy consumption is studied and an optimized reserve time set is found for the sample system.... 

The high vehicle congestion is the main contributing factor to air pollution originated from the engine's combustion in many urban areas. Grade separation projects have been used to solve this problem and have resulted in overall air pollution reduction in many cases. Many grade separation projects are constructed near sensitive urban locations accommodating susceptible individuals. This research argues that in such cases in addition to the overall air pollution reduction, air pollution concentration near sensitive locations is an influential factor for deciding the appropriate scenario. This research proposes a complementary simulation-based method for assessing the resulting pollution... 

This paper describes an attempt to develop congestion indices for a developing country with a limited sampling. Speed and flow rate information was collected from urban highway traffic flow videotaping in Iran. Video display provided information for traffic modeling when, similar to most of the developing nations, Iran does not have locally developed highway capacity manuals. Processing of the extracted data and traffic modeling provided free and capacity flow information for the selected freeway and principal arterial sections for the capital city of Tehran. The congestion indices were associated, in simple and logical models, with five traffic descriptive variables of travel speed, travel...