پژوهشنامه حمل و نقل
سال ششم شماره 1 (پیاپی 18، بهار 1388)

Models presented in the study suggest that the relationship between crash severity in urban highways and traffic variables same as traffic volume and flow speed, human factors, road, vehicle and weather conditions. Regarding that there was no model in previous works that could suggest the effects of all variables on crash severity of urban highways, models developed in current study, make it possible to investigate the effects of all the variables on crash severity, simultaneously. So, these models can be proper models in identifying the influential factors in crash severity. Thus, these models suggest that changes in crash severity doesn’t occur necessarily by any single dependent parameters, but occur as a simultaneous result of changes in these parameters.Results of the current study suggest that variables of driver age, moving on with reverse gear, technical defect of the vehicle, vehicle collision with motorcycle and bicycle, bridge, frontal impact collisions, frontal-lateral collisions and multi-vehicle crashes in urban highways are among the main factors which usually increase the crash severity in urban highways.

In this paper, we are going to schedule the train movement in one-track routes, in which, the trains could arrive to their destination at the earliest and safest way.In this problem, we consider two different directions for the trains. In the other word, there are southbound trains which travel form north to south and also northbound trains that travel from south to north. Furthermore the origins and destinations of all these trains could be different but they should be one of the stations defined in the problem.The train-scheduling problem that is defined in this project is an integer-programming problem that could be solved by current solving methods such as Brach & Bound.As the required solving time of above mentioned methods which find the optimum answer increases exponentially by the size of the problem, in order to find a good answer in an acceptable time for the real problems, Meta Heuristic algorithms such as Simulated Annealing are useful. In this paper after presenting the explanation and mathematical modeling of the train-scheduling problem, the application of the simulated annealing algorithm for problem is presented. In the next section, after tuning the parameters of the proposed algorithm using Design of Experiments method, we compare the final result of the proposed algorithm with the upper bound produced by branch and bound method using Lingo 8.0 Software. To illustrate the efficiency of the exhibited algorithm, Tehran/Bandar-abbas rail route has been selected to be scheduled. Finally the resulted timetable shows a wide improvement in comparison with the applied timetable prepared by the trail and error method used by the RAI.

In this paper, the process of data collection and prepared simulation software which is used for simulating the traffic behavior is presented. The structure of two models is introduced. One of these models is based on separation of lane changing and car following, which is similar to the most models for studying the movement behavior of vehicles. Another model is combination of lane changing and car following models, which is based on optimization process of drivers to increase speed and decrease the accident risk. The latter is based on the driving realities in some countrie's like Iran where drivers usually do not pay enough attention to driving lanes.The evermore widespread use of microscopic traffic simulation in the analysis of road systems has refocused attention on sub models, including car following and lane changing models. In this research a microscopic model is developed which combines car following and lane changing models and describes driver behavior as a utility optimization process for increasing speed along with decreasing collision risk of drivers. These models has been simulated by a cellular automata simulator and compared with the real data. It has been shown that there is no reason to consider the proposed model invalid for driver's behavior in basic segments of freeways in Iran, during not congested conditions. Considering that uncertainty of position of vehicles is caused by their acceleration or deceleration, a probability function is calibrated for calculating the presence probability of vehicles in their feasible cells. Multiplying presence probability and impact of crash, crash risk of cells is calculated. In this paper, a micro simulation model has been presented in the basic freeway section of freeways. In this model, cellular automate has been used in which freeway is derived into individual cells. Each cell at a time is empty or occupied by only one vehicle, and movement of vehicles is described by their movements in the cells. A microscopic cellular simulation software is prepared for simulating the proposed model. Comparison between simulation and real data has shown that proposed model is valid for simulating the driver's behavior in Iran freeways.

This study focuses on determining the engineering characteristics of asphalt concrete using fillers with different physical and chemical interactions properties. Mineral and Portland cement as the common fillers and nano clay and precipitated calcium carbonate (PCC) as the novel fillers. Mechanical properties that were investigated are marshall stability, flow, indirect tensile strength, resilient modulus, dynamic creep and indirect tensile fatigue. More than 200 sample were be made in size of Marshall Sample with different filler/asphalt ratio. The results show that fillers properties such as surface area have the most effect on mechanical properties of aspartic mixtures. By increasing in filler content penetration and ductility reduce and softening point increase. Silica filler have more strength under static loading but strength under cyclic loading reduces. Nano clay can improve creep behavior but fatigue life reduces. PCC have the most effect to increase fatigue life.

High population density, high traffic, air pollution and allocation of millions of dollars of subsidies for energy and fuel of the transportation sector are all amongst the major problems of Tehran metropolitan city. Through appropriate planning for the development of public transportation navigation and conservation of energy sources in the urban transportation, some of these problems may be solved or reduced. Due to the per capita space that buses occupy, these are the most suitable means for urban transportation navigation in short term and medium term programs. Gas oil and compressed natural gas are the main fuels for buses. Due to the low share of buses in the air pollution of the City of Tehran (3 – 5%), also based on the experiences of some other countries, it seems that the compressed natural gas is the best fuel for buses. The cost – benefit analysis using the net current value method regarding the natural gas and gasoline as the main fuel for the bus navigation in Tehran is illustrative of the fact that in case of increased cost of oil to more than 50 $ per gallon the reduced cost of gas –fueled vehicles and finally utilization of the income resulted from excess gasoline for development of bus navigation of Tehran, the natural gas is recommended as the suitable substitute for the gas oil, for development and renovation of bus navigation in Tehran.

The intercity road systems are of essential use for rescue and relief, aid delivery, temporary settlement and reconstruction purposes in the aftermath of major earthquakes. The lack of efficiency of Kerman-Bam road because of Bam earthquake of 2003 and the complete blockage of Chaloos road for a long time because of Firoozabad Kojoor (Baladah or Kandovan) earthquake of 2004 are just two samples which show the vital role of intercity road systems in increasing the casualty level and indirect losses of earthquakes. Therefore, seismic risk evaluation and reduction for these systems is of very great importance, especially for those countries, such as Iran, which do not have enough equipment and infrastructures and are suffering form lack of widely spread reliable transportation networks. In spite of this importance very few studies have been performed on the risk evaluation and reduction of intercity roads, and the available publications in this regard are mainly focused on the highway systems.It should be noted that there are two major differences between intercity road systems and the other lifelines: 1) the possibility of complete blockage of the road because of extensive damage to either the road body (the embankment), or landslide in trenches, or the road’s key structural components such as bridges, tunnels and culverts, while other lifeline systems are not usually totally interrupted, and can benefit from the existing redundancy, and 2) decision-making possibility of the people who are transferred by the road, as a lifeline, in the contrary to other lifelines which transfer a lifeless product such as oil, gas, or water. The decision-making possibility makes the risk evaluation and mitigation of the road system much more complicated. In this paper at first these differences and their effect on the risk management process have been thoroughly discussed, and then a risk management model has been introduced in which on the one hand all features on which the importance of a road in the transportation system of a county depends, including the capacity of passenger and cargo transfer in different seasons of the year, its classification, its service area, and so on, and on the other hand, all parameters which affect the road function in the aftermath of a major earthquake, including its vulnerability level, its geographical situation, and the possible redundancy, have been taken into consideration. The proposed risk management model is engaged with: a) complete and overall studies on two main parts of each road, namely road body and its structural components, b) definition of time- and user-dependent earthquake scenarios, and c) evaluation of earthquake economic direct and indirect losses. The proposed model have been applied to Iran intercity road system and a prioritization scheme has been suggest on this basis, which can be used by the authorities for budget assignment to various provinces of the country for upgrading the road system. A somehow new concept, which is used in this study, is “the road service area” which is defined based on a major origin-destination pair and their surrounding industrial, cultural centers, or the centers of any type of economic activity. By using this concept, each country cab be divided into some “road service areas” and then these areas can be prioritized based on various parameters, including hazard, vulnerability, and the transportation service presented in each area. For this purpose each parameter is given a weight factor and then by combining all contributing parameters with their associated weights an importance ratio can be calculated for each “service area” based on which the prioritization can be performed.The proposed “Quick Risk Assessment Method” has been applied to Iran road system, however, as the “service areas” have not been defined yet for roads in Iran, the provincial divisions have been used instead, and a table showing the prioritization factor of various provinces has been presented which can be used for making decision on the provinces which should be studied more in detail, and also for budget assignment for seismic upgrading of roads in various provinces. The main advantage of the proposed method is its simplicity. Furthermore, it is possible to add as many as desired parameters to the model without any difficulty, provided that the weight factor of that parameter can be given on a reasonable basis.

The weaving sections are developed due to meeting of two or more traffic currents passing through highways. Increasing the risk of accidents due to speed changes and maneuvering motions of vehicles as well as development of delay in freeways are amongst the issues related to weaving sections. In this research first of all the Dutch, HCM and FRESIM Methods for modeling of the weaving areas were studied. Comparing the HCM and DUTCH codes of practice shows that Dutch Model is not thoroughly mathematical and on the other side, taking into account the numerous limiting assumptions in this method, the HCM methodology was selected as the optimal method, and the travel time and delay time for various scenarios were investigated according to the volume of traffic currents, the length of weaving areas, and the percentage of the heavy vehicles. On the other hand by studying and knowing the FRESIM software and its relevant parameters the weaving area was modeled and calibrated. Then the outputs of simulation method and HCM method were compared. Results showed that despite the ability of simulation method to calculate the delays in the upper parts (reduced acceleration) and lower parts (increased acceleration), the simulation method software usually calculates less delay compared to HCM and from low to high volumes, the delay time shows a growth between %59 and %205. The trend of the increased delay in HCM is linear but the delay results by simulation method shows that in the medium volumes this trend is linear and in low and high volumes the change content is reduced. It was also concluded the despite taking into account the personal cars equivalent in the weaving areas parallel to freeway areas by HCM, this rate is different in FRESIM and its influence on the increased delay in higher volumes is higher.