JOURNAL OF TRANSPORTATION RESEARCH
Year:2011 | Volume:8 | Issue:1 (26)|Papers Count:9

Fuel is one of the most important inputs in road transportation (cargo and passenger) in Iran. Since price policies are being proposed for cutting down very high consumption of fuel in this sector, we try to find out the inflationary effects of these policies in this sector and in the whole economy. In doing this, we use input-output table of 1380 statistical center of Iran, under 3 alternative scenarios: (1) 200% increase in gasoline’s price, (2) 200% increase in gasoil’s price and (3) 200% simultaneous increase in prices of gasoline and gasoil. Our findings indicate that: under 1st scenario, inflation would rise in the cargo and passenger subsectors by 6% and 9% respectively, and in the whole economy (in case of no expected inflation) by 4.3%, under 2nd scenario, inflation would increase in the cargo and passenger subsectors by 4.2% and 4.5% respectively, and in the whole economy (in case of no expected inflation) by 2.2% and, under 3rd scenario, inflation in the cargo and passenger subsectors by 10.2% and 13.5% respectively, and in the whole economy (in case of no expected inflation) would rise by 6.5%.

Because the making and developing of metro system need a lot of investment like construction and maintenance cost, performance and effectiveness of metro design and its operational planning should be noticed. Also, metro cause directly and indirectly such effect like development of a city, mobility in economical centers, change in the pattern of trips, change land use and etc, we can lead these effect to desirable direction by correct and purposeful planning. Therefore, the optimum and correct design of metro system, specifically in network routing, is so important. For solving this problem in large network with standard and conventional methods, a lot of evaluations are needed. Usually, these methods require more time and cost, so, the necessity and tendency for heuristic method can show itself. Until now, many heuristic methods have presented for solving route generation and these problems, but most of them design one metro route and pay less attention for generating a network path and analyze them. Moreover, the parameters and constraints used in these methods are not sufficient and suitable. In this paper, we propose a heuristic method based on Genetic Algorithm to solve metro network design problem. At first, many routes are generated on the basis of proposed algorithm; and then, by Genetic Algorithm and with synthesizing routes, several networks are created; and finally, a suitable network will be selected. This proposed method is evaluated in the form of case study and its results shows that this method can be adaptable for metro network design in cities.

An experimental investigation was carried out to improve the mechanical properties of transportation concrete containing nano SiO2 by varying cement content. Compressive and tensile strength of three different cement content, 350, 400 and 450 kg/cm3, was tested in the reference and nano contained concretes. SEM photos were also used for micro structural studies. The results have shown that change of cement content causes change in strength of specimens in a convex manner with a maximum point. The addition of nano silica resulted in shifting this curve to higher cement content while the shape of curve was saved. Therefore with nano silica particles; the concrete can achieve higher strength in superior cement content. SEM observations have confirmed that nano silica can improve microstructure of concrete by decreasing the size and amount of crystals and reducing pores distribution. As observed in SEM studies, more uniform texture that produced by nano particles may put a stop to micro crack development and facilitate higher compressive and tensile strength, despite of increasing cement content.

Today’s traffic is one of the main concerns of urban managers. One of the solutions that have been proposed to reduce traffic is encourage people to use public transport instead of personal vehicles, so the quality of public transport should be increased. One way promoting public transport systems quality is creating urban traveler guidance system. In other hand, public transportation network is large and complex, also urban transportation data often is distributed and heterogeneous. In addition to, the travel route choice criteria are imprecise and uncertain. So having such characteristics, cause modeling, design and implementation of systems that can help travelers to choose their appropriate route are going to be more and more complex and difficult. We designed and implemented a travel information system for city of Tehran and named it as “TIPS”. So in this article, we illustrate the overall process of design and implementation of TIPS. The designed system will be able to acquire and combine heterogeneous data sources that are located in different places (bus, taxi and metro Inc and ...). The gathered data will be imported in a web processing service using the OGC WFS standard. Designed WPS will be able to model the multimodal network using graph theory and it also will be able to consider available uncertainty or defects in urban traveler information such as routes, stations, and travel information. In this WPS, the modeling of uncertainty are performed using fuzzy set theory. The final outputs of designed system are several ranked optimal paths between user’s selected origin and destination. The result of these study shows that the designed system in comparison with other similar designed systems is a more optimal performance and results provided by it are closer to reality.

One of the important issues in Intelligent Transportation Systems is designing and using multi-objective path finding algorithms. Such algorithms are designed to meet user satisfaction and needs through paths provided by the path finding algorithm. The conventional route planning algorithms can’t meet the user’s needs because they usually are in one-objective mode or solved in this mode. In the present study, we developed an algorithm for solving multi-objective route planning problem using a multi-objective ant algorithm in which the user defines objective functions based on her/his own needs. Then the paths are selected and ranked using the multi-objective ant colony algorithm and designed software for this purpose. This algorithm is evaluated under different conditions. The greatest strength of this algorithm is that ants choose path acting entirely in a multi-objective mode.

Track buckling is formation of large lateral misalignments due to high compressive thermal stresses in continuous welded rail (CWR) tracks and often results in catastrophic derailments. Investigating the actual behavior of this phenomenon is a complex interaction between the vertical, lateral and torsional modes. In the present study, the effects of different superstructure components such as rails, sleepers, fasteners and ballast materials on lateral stability of CWR tracks have determined utilizing a three-dimensional developed model. The parametric studies have been done for both straight and curvilinear tracks. The validity of the model is verified through comparison with theoretic results and other experimental works. The studies show that the rails and ballast materials have highly affect on track lateral stability.

The aim of this paper is to present a new solution method to optimize rail-car fleet sizing problem. The model is a dynamic and multi-periodic and car demands and travel times are assumed to be deterministic. There are important interactions between decisions on sizing a rail car fleet and utilizing that fleet. Consequently, using empty rail-cars is considered in the proposed model that leads to a high decrease of fleets number and costs. The model also provides rail network information such as unmet demands, number of stationed rail-car in each station and each time period, and number of loaded and empty traveling rail-car at any given time. In this paper, the proposed solution procedure is combining Genetic Algorithm (GA) and Simulated Annealing (SA) algorithms. GA is used for determining the number of fleets in each station at the beginning of the planning horizon, and SA is used for assigning rail-cars to demands in the length of the planning horizon. Computational results demonstrate the applicability of the proposed approach. For evaluating the proposed solution method, a comparison between results of the hybrid metaheuristic algorithm and optimum results of CPLEX software is done. The efficiency and effectiveness of the proposed hybrid algorithm is revealed.

Inaccurate understand of creep behavior of the rocks and application of inappropriate behavior models can lead in uncompensable damages in the tunnel analysis and design. Fortunately, study of time-dependent behavior of rocks has been taken into consideration in recent years and even it has been considered in many of the most applicable soft wares such as FLAC. In this paper, the time-dependent behavior models of Maxwell, Kelvin-voit, Burger and CVISC have been presented. Subsequently, these models have been analyzed in the finite difference program of FLAC in a circular tunnel model in a hydrostatic condition, thereafter; the analysis results have been compared. Improving these models, a time-dependent model has been proposed and its performance has been verified by comparison with mentioned models. The most important attribute of the proposed model in this paper, is its advantages to take all three stages in rock masses creeping into consideration (this phenomenon occurs in high stress zones in deep part of rock masses). Furthermore, this model has the advantage of describing the softening behavior in stress-strain curve based on the reduction in rock mechanical parameters (In confronting to tertiary creep).