JOURNAL OF TRANSPORTATION RESEARCH
Year:2005 | Volume:1 | Issue:1|Papers Count:8

The planning of train schedule is based on regular intervals and it forms the most crucial task in railroad operations planning. It is usually constructed from the perspective such as time, distance, cost, capacity, etc... However the nature or the train schedule planning problem is inherently multi objective. In this paper, multi objective programming techniques have been developed to provide the decision makers with explicit consideration of the relative values of the objectives. Minimizing the operator's total operating cost and minimizing the passenger's total travel time loss are the two planning objectives of the model. It determines the best compromise train service plan, including the stop schedule plan, service frequency and fleet size. An empirical study on Tehran - Doroud railway results the fact that we will nee nine couple passenger trains and eighteen couple load trains to have the best level of service in this track.

An attempt has been made in this paper, to develop models for bridge repair and maintenance activities in which the assignment of resources has taken place in an optimized procedure, and the resulted benefits in the roads network are maximized. One of the major characteristics of the developed models is the ability of multi-period optimization. By integration of internal and external models, a new prioritization approach has been developed. Using the new models, the loss of benefit in the whole bridge network would be minimized. The optimization network models are able, not only to determine the appropriate time for implementation of repair and maintenance activities, but also for allocation of limited resources to the bridge projects.

The Vehicle Routing Problem with backhaul (VRPB) is one of the prominent branches of the famous Vehicle Routing Problem (VRP) in which based on the principles of VRP, the operation of empty trucks on return trips is prohibited. In this paper, a 0-1 integer programming model for the VRPB is presented. In addition, two heuristic algorithms to solve the problem have been proposed. Some test problems are generated regarding the literature and solved by the proposed heuristic algorithms. Finally, results with the two heuristics are compared to each other and with the optimum solution obtained by solving the 0-12 integer programming model.

High speed trains technology has speeded up to the practical velocity of 515v Km/h and in this regard TGV technology has a leading role. After damaging the concrete bridge Lyon-Paris for high speed trains bridges design codes have upgraded to new approaches to deal with high speed bridge design. The last modification in bridge design codes, regarding high speed trains were related to IAPF and EURO Code, which considered special regulations regarding the high speed rail road bridges. Meanwhile, Japan, Korea, France, Spain and Sweden have also set up some regulations in their corresponding codes. The importance of high velocities is due to the fact that stresses and deflections are increased compared to static cases. This results serial problems for these structures under their service loads. In this paper the bridge structures under different speeds are analyzed and their resonance conditions are specified. Finally dynamic impact factor for three design parameters, i.e. deflection, bending moment and shear force at different speeds and spans are calculated and their changes are traced with respect to velocity and span changes.

The construction of new freeways generates new traffic currents. This generated traffic is partially due to diversion from the other highways and partly because of the latent demand that associated with latent demand. In this paper, the results of modeling diverted as well as induced traffic in a few intercity freeways of Iran are presented. For the diverted traffic a linear utility function along with a Logit route choice model is calibrated for various vehicles. In addition for the induced traffic an induction factor is modeled based on the trend analysis of traffic data.

With considerable dispersion in many areas of the world, sand sediments are among the most important sediments in deserted environments. A stabilization method for this type of beds is making use of the setting property of natural pozzolana in the vicinity of lime. These soils have little strength, both in natural humidity as well as in full saturation conditions. Their dispersion in many areas of the world is another important point about them which adds to the significance of this study. In this study an experimental investigation has been carried out on two types of soils (taken from two different beds), and the results have been presented in strength gain diagrams, in different curing periods, and the changes that occurred when different percentages of pozzolanas were used are shown. Referring to these diagrams and results of durability tests with different freeze-thaw cycles, a percentage of pozzolana has been recommended that, from durability point of view in this type of beds that makes it possible to construct the required routes on these beds.

Inter-city transportation has major differences with urban transportation. These differences were reasons of using a different method in the present paper. Studying the manner of traffic assignment in roads of the country (especially those with highway and rural road together) and also analyzing driver's behavior, the obtained results showed that characteristics and attributes of ways have crucial impact on route choice. So, the models with utility functions were considered and Logit models were selected due to their popularity and usefulness in such cases. Another object, important in the development of traffic assignment model between highways and rural roads, was the role of the type of vehicle used on route choice. Therefore, in addition to the route choice method, impact of vehicle type was also considered, which lead to development of process and simultaneous models of vehicle - route. For development of the models some information were needed information, about route choice. These information should have been provided by the main users of roads, the drivers and their main reasons for their specific choices. For this reason a questionnaire was designed and distributed among drivers. On the basis of the collected data, several models were developed. The comparison between models showed that those models in which the vehicle type is chosen as the first parameter and the route is taken as the second parameter are more compatible in Iranian circumstances.

Linear programming is one of the strong tools enabling managers and decision makers to allocate limited and competitive resources in a rational and scientific manner. AASHTO method is a common and famous method which leads to several linear constraints. In this paper a linear programming model is developed for determining an optimum thickness for each pavement layer. Using this model gives a unique solution for thickness of any layer that needs minimum investment for pavement construction. Results show that there is a relationship between pavement configuration and optimum thickness and the ratio of construction costs. As long as the ratio of construction cost is less than the layer coefficient, the thickness of this layer should be increased in order to result in a cost effective pavement.