پژوهشنامه حمل و نقل
سال دوم شماره 1 (پیاپی 2، بهار 1384)

In this paper analysis of accident data of two – lanes rural roads of the province of Boushehr is presented. In this analysis, the contribution of important factors such as driver, vehicle and roadway width and pavement surface characteristics that are effective in the occurrence of road accidents are pointed out. A survey study was then conducted on 21 km. length road sections of the rural roads in the province. The Skid Numbers (SN) of the pavement of these sections was measured and their Pavement Condition Index (PCI) was calculated. Eventually, based on the analyses of accident data collected for the sections, a mathematical model is proposed that relates the accident rate (AR) of the sections to their pavement surface conditions, namely Roadway Width (RW) and Average Daily Traffic (ADT).

Value of time is one of the most important economic parameters in the field of transportation engineering. This parameter has been frequently used in economic evaluation of transportation projects and is an essential factor for this purpose. There are a few methods for assessment of VOT each of which is based on its special base and therefore their work areas are different. This paper tries to introduce various VOT methods and modified methods are also represented for each of them. Models related to each of these models are then made and their weakness and power points are discussed. Models are designed for Kermanshah City and various data collection procedures have been used for them.

In this paper, dynamic analytical model of train bridge system is established, with the vehicle wheel hunting as the self excitation of the system. The train bridge system equilibrium equations are derived and computer software for solving the problem is worked out. Whole histories of the train passing through the bridge are simulated on computer. Dynamic responses of the truss and their distribution s versus train speeds are calculated and are compared with those from field measurements. Discussions are concentrated on spatial coupling problems occurring in a real double track truss bridge acted on by a train running at speeds of 100 km/h – 300 km/h.Results of calculations and measurements show that the hunting movement of train wheel sets and the deflection of truss stringer play important roles in the train-truss system vibration. At certain train speeds, the excitation a case either the lateral or the vertical responses of both are amplified. Also, as for a double track truss bridge, the lateral and the vertical vibrations are coupled with each other when a train runs on one track. The torsional vibration induced by eccentric loading makes the lateral displacements and the amplitude greater. This should be taken into account in dynamic analysis and design of high speed railway bridge.

The optimal section of various road corridors specially freeways an highways, as the main ground transportation routes considering the economic costs of these structures is the main subject of this paper. The paper deals mainly with the costs of construction and utilization of freeways and highways including expenditures relating to infrastructure and pavements of roads, traffic, utilization, travel time, accidents, pay tolls and fuel consumption. The costs and benefits resulted from construction and utilization of these two options is compared separately with the two – lane roads. The obtained result of cost benefit analysis determines the best economic option. Besides the computation of the developed models, the relationship of variables such as road alignment, traffic characteristics, geometric design standards and economic factors were calculated. To evaluate different alternatives, a paired comparison methods as well as he major routes in Iran was chosen for the case study.

Fog is one of the meteorological events, which decreases horizontal and vertical visibility. Despite of usefulness in agriculture and protection for plants freezing; it has an important role in life and poverty damages in transportation section. This natural and destructive event causes major difficulties in aviation and prevents from flight operations. Generally, in order to fog dispersion and clearing weather, at first, it should be get knowledge of formation and types of fog and investigate this important meteorological event in detail, then the method of application of new technologies, such as fog dissipation using cloud seeding technology and also it’s application should be performed. Therefore, in this paper, after a review on formation and physical construction of fog, long term data and diagrams of foggy days in 30 cities of Iran country and zoning maps have been produced, then field research results of fog dissipation in different regions of Iran has been discussed.The result of field test indicates cloud seeding method using liquid carbon dioxide by moving vehicle for supercooled fog as one of the best methods, which causes clearing weather and increasing visibility field after 30 minutes. The successful results of this test indicate this fact which successful cloud seeding methods could be applied for fog dissipation and clearing atmosphere. In Last part of paper, numerical microphysical processes of supercooled cloud seeding have been discussed.

Islamic revolution, the imposed war and oil export fluctuation were the three important events that occurred during the last 35 years in Iran. These events affected almost all aspects of economic status in the country. In this paper, four econometrical models are developed to determine the important factors affecting the valued added of transportation sector and GDP and their reciprocally impacts on each other during these years.Results may be classified into three major points; negative effects of governing regime on the relative importance of transportation sector, negative impacts of the imposed war on real GDP of Iran and consequently on transportation sector, high dependency of transportation sector on oil exports.