JOURNAL OF TRANSPORTATION RESEARCH
Year:2013 | Volume:9 | Issue:4 (33)|Papers Count:8

Two lane two-way highways comprise major portion of national highway network. They provide the possibility of overtaking in opposite direction of flow. The capacity of these highways is an important parameter in their design and efficiency. High percentage of heavy vehicle traffic imposes adverse impacts on their capacity and level of service, particularly at the slopes. “Passenger Car Equivalent” concept is used for accounting the effect of such vehicles on service quality and highway capacity. In this research, two methods of “speed difference” and “headway” were used for determining the coefficients of “Passenger Car Equivalent”. In this research, nine two-lane highway sections were selected in different geographic, weather, topographic and volume conditions for data gathering. A new vehicle classification were proposed and used instead of the formal classification of highway transportation and maintenance organization. The obtained results were compared. The comparisons indicate that the methods give close results. In addition, the results show that obtained passenger car equivalent coefficients are generally less than the corresponding values in HCM 2010 and the difference increases with slope.

The flow field around each moving vehicle experiences the pressure and velocity changes.The pressure in front of the vehicle increases while the pressure behind it decreases. This phenomenon, which is more pronounced in closed space like tunnels, is called piston effect.When the train enters the tunnel a compression wave would be generated and propagates along the tunnel which causes the most and the first pressure rise along the tunnel. The compression wave along with an expansion wave of the train tail severely affects the pressure and velocity distributions in the tunnel and around the train. In this research, firstly the results were compared with experimental data available in the literatures to verify the accuracy of the present numerical model. Then the flow field around the train in different time steps was obtained. The results show that, in each time step, the most pressure and velocity changes along the tunnel, occurs around the train body. The maximum velocity magnitude is around the train rear and the highest pressure magnitude is around the train head except at the time of train negative acceleration, which the pressure magnitude is maximum at the rear of the train.Finally, the interaction of the fans near the tunnel inlet and outlet and train movement was investigated which results show that when the fan is in operation, the separation bubble on the train top would be larger which leads to increase in the first pressure rise due to train entry to the tunnel. In addition the inlet and outlet flow to the tunnel from stations change remarkably due to train movement.

Urban bus transportation is one of the common public transportation modes, which has a significant position among all other modes. Any attempt in order to increase the effectiveness and desirability of this mode has a positive influence on the urban trips. Bus network design due to its considerable influence on the performance of this mode is of great importance. And various approaches have been proposed in this context, which have different advantages and disadvantages. Reaching the optimal network in the shortest possible time, considering the parameters which are in conflict with each other most of the time, is the main reason of the complexity of bus network design problem, and makes constraints for the designers. The present paper proposes a heuristic approach for solving bus network design, which is based on graph theory. The proposed methodology designs bus network in two steps of route generating and route selection. For the evaluation purpose, this method compared to other heuristic methods. The results showed that the proposed method outperforms the other existing heuristic network design methods.

One of the problems in bridge design is the uncertainty in codes in defining the role of Neoprene comparing with the bridges with directly pier to deck connection (voided slab). In this study for investigation of the R factor, five models with a Neoprene connection between substructure and superstructure, and two models with direct connection between the pier and the voided slab, are developed.The average values of the R factor in the models with Neoprene were 4.28 in longitudinal direction and 5.90 in transverse direction. These values in the code are 3 and 5 respectively, showing that recommended R-Factors in code are conservative. Also in the bridges with directly pier to deck connection, the R factor in longitudinal direction was 2.92 that is close to the value in the code (equal to 3), but in transverse direction it was 2.41 that is half of the given value in the code (equal to 5).

Retaining walls are one of the popular earth structures for which a comprehensive recognition of soil-structure interaction is of importance issue. Among these retaining walls, the integral bridge abutment as a special type of retaining wall is subject to cyclic displacement, which is due to the daily and seasonal temperature variations. These bridges, known as bridges with rigid frames or joint-less bridges, are constructed so that the top deck is longitudinally continuous. The elimination of expansion and shrinkage joints causes a fluent traffic and a reduction in maintenance and repair of the bridge. In the other word, the expansion joints, which are widely used in traditional bridges, are removed in this type of bridges. Obviously, the imposed movement to the deck of bridge is transmitted to the top of the abutment, resulting in cyclic displacement of the top of the abutment. In this research, the finite element program Plaxis 2D was used to study the effect of cyclic displacements on the passive pressure of abutments integral bridge. Using this program, the analysis in many different conditions on a model abutment was carried out. To calibrate the numerical model, an innovative laboratory retaining wall model has been designed and constructed. The results of numerical model were calibrated using the laboratory test data. The results indicate that the passive pressure distribution, except for low amplitude displacement, is non-linear, which is due to the arch forming. In addition, the maximum passive pressure value along the wall is dependent on the magnitude of the wall rotation and number of cycle.

Control problems and consequences of population growth that has taken many measures that implement a traffic plan that can be cited. The economic implications of the price range of traffic rules stating that users of high-traffic thoroughfares that pass, In order to maximize social network benefits must equal the difference between cost and social cost of and the cost of final average pay. Knowledge of data mining as one of the most effective way optimization of traffic in the traffic plan to investigate the impact of transition on the types of violations and obtain the rules in this area is considered. Using a genetic algorithm as one of the data mining methods and to consider more factors and parameters and the combination of the methods employed by in the previous study, an effective measure in reducing and controlling traffic in the streets was done. Therefore, this paper has tried to use genetic algorithms as well as Frank algorithm - Wolf, who studied the issue has been adapted Price is optimal for traffic modeling. The article uses the example of an algorithm implemented.

The railway capacity analysis methods have a great effect in better use of existing infrastructure and location optimization for new infrastructure. Capacity consumption is measured by infrastructure occupation in a defined time window. The common method for calculating the capacity consumption in the railways is UIC406 presented by International Union of Railways. In this paper, the capacity consumption in Iran Railways is calculated using UIC406 method. In UIC406 method, the choice of line section on which the compression methodology will be applied is a key issue. In this paper, the choice of line section has been suggested for Iran Railways. Capacity consumption and optimum capacity is calculated in Tehran-Mashhad line as a case study and the results are reported.