JOURNAL OF TRANSPORTATION RESEARCH
Year:2012 | Volume:8 | Issue:4 (29)|Papers Count:7

In this paper, a fuzzy multiple attribute decision making model is proposed for selecting the best alternative for investment in transportation projects, which is based on group decision methods. To this end, the fuzzy Topsis method has been applied along with qualitative and quantitative criteria for decision making. "Confirmatory Factor Analysis" has also been used to determine the decision criteria. In order to incorporate the vagueness of the information, trapezoidal-fuzzy numbers are used in this study. To determine the weights of decision criteria, these authors used the "Fuzzy Delphi" method. To implement the proposed selection procedure, this study uses data from the "Oroomieh" region as a case study. The results were validated by the experts who contributed to this research. The PROMETHEE as another multi-criteria decision making method, is also utilized to demonstrate the appropriateness of the application of Fuzzy Topsis in this study.

Transportation network design is one of the most important issues in transportation engineering, which is complicated by uncertainty. Uncertainty in demand is one of the most common types of uncertainty in traffic networks, which comes from various sources such as difficulties in forecasting of trip productions and attractions. In this paper, a method based on robust optimization for discrete network design in scenario-based variable demand conditions is used, in which the level of imposed uncertainty of that problem will depend on designer choice. For this reason, the objective functions of weighted mean and variance total travel time in several demand scenarios are implemented; and for solving that problem, genetic and ant colony algorithms are used. To examine the proposed model, two case studies are applied to an ordinary network. In the first one, the demand pattern in hypothetical scenarios has a high disparity, and the variance of total travel time is more important in the final design than the mean. In the second case study, the demand pattern has a low disparity, and the weight of the mean and variance is more significant in the design solution. Based on two conditions, the results of design in the condition of uncertainty are different with independent design of each scenario, which emphasizes the use of optimization methods in conditions of uncertainty to solve similar problems. Also, in comparison of genetic and ant colony algorithms in various weights of the objective function, the ant colony algorithm found better solutions with less calculation effort.

This paper presents a new method for solution of a vehicle routing problem, which considers a balance of goods based on the vehicles’ capacity. A considerable part of the drivers’ benefits is related to their quantity of sales; therefore, the balance of goods based on vehicles’ capacities is important to obtain drivers’ satisfaction. This is one of the objectives of this paper, alongside minimizing the travel costs. Due to the complexity of solving such a difficult problem with exact methods in large-scale applications, a meta-heuristic method based on improved particle swarm optimization (IPSO) has been proposed. In addition, to show the efficiency of the proposed IPSO, a number of test problems in both small and large scales have been considered and solved. Then, the results obtained by calculation have been evaluated with the results obtained by the Lingo software. Furthermore, to run the proposed IPSO, a real case study in a dairy company located in Qazvin with 152 customers has been studied, and finally, the obtained results have been reported and discussed.

Due to an increase in goods transportation and movement of heavy gravity vehicles, high-volume freeway routes include a level of safety reduction. The aim of this study is to explore the effect of heavy gravity vehicles restriction on passenger vehicles to reduce their interactions, which is necessary for the use of special lanes or lane restriction for heavy gravity vehicles. Lane restriction for heavy gravity vehicles is a method that is commonly employed in this country, but is lacking any detailed academic studies. In addition, this paper presents efforts to determine a comprehensive and suitable criterion for specifying appropriate use of lane restrictions on a freeway or highway. In this research, the presence or absence of lane restrictions for freeways in Iran are investigated, along with a comparison of those two modes and the influence of several parameters on that process. To this end, in order to compare the scenarios, the traffic simulation software VISSIM and a section of the Tehran-Qom freeway was used as a case study. Also, in order to evaluate safety, the SSAM software was used, and to ensure maximum compatibility with the specified situation, its calibration and validity was examined. From this research, the presence of lane restrictions for heavy gravity vehicles was shown to improve operational performance by about 4%, and in terms of safety, the presence of lane restrictions was shown to be somewhat weaker than the lack of them. This conflict between operational performance increment and safety reduction based on lane restriction is related to the accumulation of heavy gravity vehicles in right-hand lanes and the complications of vehicles changing lanes for exit from the freeway and entering the ramp.

In the railway transportation industry, the rail is considered to be the dominant source of rolling noise over the usual speed range (<160km/h). It has been well documented that the rate of decay of vibration along the rail is closely linked to the noise performance of the track. In this study, a finite element model of a periodic supported rail is developed in ABAQUS to study the acoustic performance of the rail. To compute the decay rates, acceleration responses along the rail are converted into the frequency domain and then the decay rates are obtained for each 1/3 octave band by processing the response levels. It is shown that the decay rate results obtained by FEM follow the same trend as the measured decay rate. Therefore the FEM decay rate can be used for generating comparisons between different tracks as an indicator of their acoustic performance. To test the vertical decay rate on a real track, a rail section at the Sadeghieh subway site is also tested and analyzed. To this end, the vertical responses of the rail are measured by two accelerometers. It is shown that at low frequencies (below the cut-on frequency), the decay rate resulting from the accelerometer on the sleeper place is 2dB less than the decay rate result from the accelerometer on the mid–point. However at high frequencies (above cut-on frequency), the decay rate results from both accelerometers correspond closely to each other.

In this paper, an electrical charge model was developed as a microscopic traffic model for describing a driver’s behavior in a basic section of the freeway. This model has been simulated with a cellular automata simulator and compared with real data. In this model, the behavior of a car is represented as similar to electrical charge behaviors, where it is considered to move in a sloping path. In this model, for any car in a time phase, the electrical power from the other cars and the car itself was considered. On the basis of this power, the location of the car in the next time phase was then determined. In this study, two models designated EM1 and EM2 were proposed for drivers in Tehran. For investigating drivers’ movement behaviors in a basic section of the highways in Tehran, some previous research and recorded data was applied from the Tehran–Karaj freeway. In addition, the study employed the use of micro-simulator software in order to simulate the proposed models. This software has shown that there is no reason to consider the last model invalid for drivers' behaviors in a basic section of freeways in Tehran, during not-congested conditions. By comparing the location of the vehicles under real conditions with parallel quantities of them in the simulated medium, the correspondence level has been determined between each of the models and the drivers’ behaviors in the real data. Comparison of the obtained results derived from simulation with the real data has demonstrated the EM2 model corresponds well with the behavior of real drivers in a basic section of Tehran's freeways.

Construction of high speed railways is booming in the world. One of the main issues related to high speed railway is the non-uniform deflection of the rail along the track due to increases in train speed. This study focuses on investigations of the influences of strain speeds on track defections. For this propose, a model of railway track was developed. This model was then calibrated using field results available in the literature. The results of model calibration indicate that the consideration of the track support system nonlinearity has substantially effects on the theoretical results, concluding that the incorporation of the support system nonlinearity is a need in track modeling. From sensitivity analyses of the calibrated model, the effects of increases in train speeds on track deflections were investigated. It is shown that track deflections increase as the train speed increases up to the speed of 140 km/h. However, after this speed, the deflections of the track slightly reduce. It indicates that the critical speed of the track from the deflection point of view is 140 km/h. Research findings here indicate the necessity of further consideration of the critical speed in the design of high speed tracks.