پژوهشنامه حمل و نقل
سال پنجم شماره 3 (پیاپی 16، پاییز 1387)

Carriage of dangerous goods, in comparison to transportation of other goods, does not follow independence rules. This fact is increasing probability of damage imposition to unknown persons and environment, without none or incomplete remedies. On the other hand in detriment assessment and its measures, less consideration has been devoted to the type of goods. In this paper the safety obligation of carrier and other related persons in carriage of Hazard goods is discussed. The analyses of subject has been completed by a comparative study in the law of Iran and other countries who specifically regarded the issue of Safety Obligation in Carriage of Dangerous Goods. From the laws point of view, there are some theories about the nature of liability such as fault, risk and absolute liability. In safety obligation of carrier, it seems that a better theory that assured third persons rights is “Strict Liability”. This theory means that a carrier of hazardous goods has liability in ever and proving justification factors such as force major does not exempt for liability. From this point of view dangerous goods liability has been compared to nuclear materials and wastes transportation. This is correct because the objectives of law is almost the same and the similarity of these goods in danger and risk of involvement of many neutral persons in detriments of accident like explosion, fire, corrosive and etc. Albeit the conventions and national statutes on liability for nuclear damages have not been analysis separately due to the fact that it requires a separate study and includes almost a different regime than hazardous goods. Unfortunately, unlike nuclear materials, there is no universal convention in different legal aspects of transportation of hazardous goods. Accordingly the unrivaled thought of establishment a perspicuous regime for strict liability, insurance coverage and preparing a bill of precaution measure for transportation and maintenance of dangerous goods is very necessary. After a short discussion on the definition and various types of dangerous goods, all of these ideas have remarked in this paper with a comparative study about safety obligation of carrier in transportation of dangerous goods.

Vanadium is one of the best elements used to improve the mechanical properties and wear resistance. In this work, the effect of vanadium on mechanical and wear properties of thermit welded medium carbon steel rail are investigated by various quantities of vanadium added to the thermit powder before welding. The results show that the microstructure of weld zone includes p roeutectoid ferrite at grain boundary and as blocky shape in pearlitic matrix. Vanadium increases the amount of ferrite, and decreases the amount of pearlite in weld zone. The investigation on the mechanical properties also shows that, addition of vanadium in thermit welding leads to achieve higher hardness and wear resistance in this region. Increasing the vanadium, also increases the ultimate strength, elongation and toughness properties, but gradually these properties are decreased. Increasing vanadium up to 0.1-0.15% leads to increase the elongation and toughness but the higher amounts of vanadium reduce the tensile and toughness properties.

With the increasing demand for public transportation due to congested city highways and streets, the rail systems and especially metro have become one of the most viable alternatives for daily commuting. While city planners are excited with the increasing public transportation rider ship, they are also challenged with a higher volume of passenger flow and longer queuing lines at the existing stations and of course, metro platforms.One of the most useful features to improve the current situation and plan for the future, is using simulation tools to help the planner how to evaluate system operation design, queue management, fare equipment design and fare policy impacts, all in virtual and dummy world.In this study, Co- ordination of headways between entrance of passengers to metro station, and arrival of metro trains that travel by fixed scheduling is proposed. The objectives for the study, are development a simulation model to analyze the passenger waiting time of an urban metro stations with other modes of feeder services. Urban metro system is characterized by its comparatively short headway and fixed schedules. Thus, the behavior of passengers in urban metro is significantly different from the behavior of passengers in intercity train or bus system. If the entrance of passengers from other modes like buses, taxies, walking and etc. To metro station considered as a major feeder system for the urban metro, passenger waiting time and related behaviors of the urban metro station should be influenced by the reliability of train scheduling that the most important part is average headway between arrival of each metro trains.So, in this study by using simulation technique, a reliable simulation model for passenger and metro train that named as "METSIM Software", where designed.The results provide planners with an analytic model for accurately quantifying the relation between passenger waiting time of urban metro system and the reliability of other variables like headway of arrival metro trains due to fixed scheduling, passenger flow entrance rate from other feeder services to the station, fare policy and the equipment that presented at ticket hall for fare collection (like ticket vending machine, waiting in queue lines for buying paper tickets or credit cards, and ticket acceptance gates).

During the last decade, application of pushover analysis in seismic assessment of structures is increased. Pushover analysis provides crucial information on responses of structures that cannot be obtained through conventional linear static methods. However this method suffers from some drawbacks. The major drawback of the conventional pushover is that it is basically restricted to a single-mode response, and cannot account for the contributions of the higher modes and also the progressive change in the modes shapes because of structural yielding. To remedy this shortcoming, recent years have witnessed the development of some adaptive modal pushover methods. These methods obviously consider the effects of the higher modes and progressive variation in the dynamic attribute of the structure in the inelastic phase. However, these advanced methods are generally proposed for building structures and their application to bridges is questionable. In order to extend the application of these methods to bridge structures, the differences in the structural system of buildings and bridges should be considered. In the common pushover methods proposed for buildings, the top storey displacement is used as displacement character in pushover curve while, in the bridge structure selection of each support displacement as displacement character are disputable. In this paper an advanced adaptive modal pushover method is proposed for seismic assessment of bridge structures. The proposed method takes into account the higher modes effects and progressive change in modal properties. This new method incorporates the adaptive pushover method in multi modal pushover analysis. In fact in the proposed method, three main concepts: 1) modal combination, 2) adaptive load pattern and 3) energy based pushover curve are used and their advantages are combined together. In the proposed method the pushover curve is provided individually for each mode. The pushover curve of the multi degree of freedom system (MDOF) is converted to the single degree of freedom system (SDOF) curve with unit mass. In each load step based on the simultaneous mode shape and energy concept, the MDOF system curve is converted to a SDOF system. Since the energy concept is used to define the capacity curve, the values and signs of the displacements in all support are considered. Therefore the ambiguity in selection of the support as control point (displacement character) is removed. In each step the increment of the displacement in the SDOF system is defined based on sum of the work done at each support level through each incremental force. At each step, the total work done in all supports is assumed to be equal to the work done by the total base shear. The proposed method is applied to an irregular four span viaduct under Tabas earthquake records. It illustrates a good estimation of the peak displacement response in the inelastic phase.

This paper aims to solve a locomotive routing through a rail network that is important for railway companies, in view of the high cost of operating locomotives. The locomotive routing problem finds the least cost routes to assign a set of locomotives locating in a central depot to a set of trains in a pre-planned train schedule so as to provide them with sufficient power to haul the trains from the origins to their destinations. In this research the well known vehicle routing problem with time windows is considered to be the basis for modeling the locomotive routing problem. Vehicle routing problem with time windows (VRPTW) is an important variant of vehicle routing problem (VRP) with adding time windows constraints to the model. In this problem the vehicles that are located a depot must serve a number of customers within predefined soft/hard time windows at minimum cost, without violating the capacity and total trip time constraints for each vehicle. This paper first reviews the literature of VRPTW and locomotive routing problem and after defining the locomotive routing model, designs an efficient genetic algorithm with special operators to solve it. In the proposed genetic algorithm part of the initial population is initialized randomly and part is initialized using Push Forward Insertion Heuristic (PFIH) method. Having non-random part of the population greatly reduces the time for the solution to converge, and having a random part prevents sticking to a local optimum and not exploring the complete solution space. Candidate solutions for mating are selected using the tournament selection that in which two identical (through differently ordered) copies of the population is kept and in every generation, adjacent chromosomes are compared in one copy of the population pair by pair, and one chromosome with best fitness value is selected to insert to the mating pool. Then this procedure is proceeding with the second copy of the population to select the other half of the chromosomes. The proposed genetic algorithm employs two kinds of crossover operators namely heuristic and merge crossover that they tries to produced solutions with better time and distance travel cost. Also, the mutation schemes that are used in suggestive algorithm are swap node and swap sequence that they applied on chromosomes with special mutation probability scheme which changes the mutation probability as the standard deviation of the population fitness changes.The suggestive genetic algorithm uses a famous local heuristics namely λ-interchange mechanism to search the neighborhood and larger area of solution space and also make improvements on produced solutions. This mechanism incorporates two strategies namely one-interchange (FB) and two-interchange (GB) to search for better routing solutions. The former tries to find the first better solution in short time and the latter finds the best solutions during some changes. Also at the end of each generation, elitism and recovery strategy is used to keep a few numbers of good individuals. It is notable to mention that the algorithm reduces the exponential computational complexity of the problem to a polynomial one which is an advantage for the solution algorithm. Two different scenarios are presented and their results are compared. To check the validity of the method, results gained by the algorithm are compared with the ones from an optimizer solver. Moreover, a test problem with small size is solved step by step according to suggestive method to clarify the concept of the model. The results indicate good quality and time saving of the method.

In this paper dynamic performance of a passenger coach is investigated in higher speeds in presence of rail surface irregularities. The research is directed to study how the increasing of the operating speed may affect two important dynamic parameters i.e. ride quality index as well as the fatigue life of the springs used in both primary and secondary suspension systems. Rail surface corrugation is modeled by its Power Spectral Density (PSD) for three classes of rails according to the USA classifications of tracks. Using random vibration theory, dynamic matrix of the system (H(ω)) is obtained and then for the response matrix of the system one can find:

Road Meteorology is one of the subjects related to the role of weather forecasting in road transportation safety. During recent years, there has been great development in application of meteorology in road safety and Road Weather Information Systems. Necessity of informing the road users, managers and road keepers about road conditions as well as fast development of observation and early warning systems, have put great emphasis on studying meteorology and its application in road transportation systems. Road weather information system includes road and meteorological sensors which have important roles in intelligent transportation system (ITS). In this paper, roads between Tehran and Karaj have been studied for site selection of black spots and installation of sensors. Based on analysis of meteorological, traffic and Accidents data, some points have been selected as suitable sites for installation of road weather information system.