نشریه فناوری حمل و نقل
پیاپی 31 (پاییز و زمستان 1397)

Intersections are the main gorge of traffic in the cities and roundabouts have become one of the popular options for intersections traffic management because of their positive features in terms of capacity, performance and safety. Conducted comparisons between controlled intersections and roundabouts by different researchers shows that roundabouts have lower latency and greater safety than intersections. This operation depends largely on their geometric design. Older roundabouts are facing traffic and safety problems due to poor design of entries, exits, circulating lane width, pedestrian crossing location and central island. Therefore, they are close to locking in peak hours and have low safety in off-peak hours. In fact, with the presence of weaving movements, high difference in speed and improper angle between entry and circulating approach, failure to provide adequate stopping sight distances, inadequate angles between the approaches and the lack of proper signs and line marking, the operation of older roundabouts have changed to the one's for the traffic circles. Therefore, this study attempts to identify the weaknesses in the design and performance of roundabouts and provide solutions for resolving them by understanding the characteristics of modern roundabouts and their differences to other traffic circles and also studying the previous field studies on roundabouts in different cities of Iran and other countries.

In this paper, using domestic and foreign experiences in the field of safety, environment and health management system, as well as the characteristics of rail and road development projects, based on PDCA approach (plan, Do, Check, action), A pattern consisting of 16 main clauses is provided for deployment in these plans. For this purpose, In the first phase, after reviewing the background of foreign experiences and Performing initial content analysis, elements of HSE management systems were extracted. Then, in order to determine the localization considerations for the establishment of these systems in Iran, examples of similar work records in the country were studied. In the next phase, by reviewing the documents and using Delphi method and its subdivisions and examples of rail and road development plans, the strengths and weaknesses of the current HSE situation based on the approach of management systems and also the list of features of rail and road development plans were extracted for application in the model. Finally, using the mentioned studies, HSE management system model for rail and road development projects was presented and for model validation, it was deployed in a complex (General Administration of Region 6 of Construction and Development Company) as a pilot and some problems and obstacles to its establishment were identified.

Roller compacted concrete (RCC) nowadays is majorly used in two quite different fields. The first application of RCC is in the dam construction and the second is as the pavement. One of the most important parameters in the implementation of concrete structures is their durability, this is especially crucial for pavements which face with harsh enviroments and countinous dynamical loads. Regarding the using of RCC pavements in areas with various environmental conditions assesing the durability parameters of RCCP are very important. Carbonation is one of most important phenomones which affect the durability of concrete structures. The main purpose of this research was to investigate the effects of the carbonation phenomenon on durability properties of RCCP. In order to achieve this aim, RCC with 0.32 constant water-cement ratio in grades of 270, 300, 330 and 350 cement content were made and compressive strength tests, capillary absorption and carbonation resistance tests at the ages of 7, 28 and 90 days were carried out. If the carbon dioxide penetrates through RCC samples, the compressive strength decreases with regard to increasing the age of the samples. With the aging of samples, capillary water absorption is reduced due to the completion of the process of hydration which reduces the pores. The capillary absorption for carbonated samples compared with the same specimens relieve that carbonated and non-carbonated samples has few diffrence in terms of capillary water absorbtion. Overal the results which confirm each other suggest that, the increase in cement content have improved the durability parameters. It was also shown that carbonation phenomenon has not significant influence on physical performance and durability properties of RCCP. As a result, it can be said that the use of RCCP in urban environments where the phenomenon of carbonation is more likely, is permitted. This study also, encourages the application of RCCP in terms of resistance toward carbonation phenomon.

One of the most effective factors regarding the design of airfield concrete pavements is its performance relative to the temperature and static load caused by airplane traffic. This research aims at evaluation of tensions and deformations occurring in concrete slabs at the airfield concrete pavements, arising from temperature variations and the layout of the aircraft wheels design (Airbus 320), in the 3D model and in the SAFE software environment. By analyzing models and outcomes, it is observed that tensions and displacements and deformations created in the slabs under load caused by the temperature, are much higher than the wheel load. Furthermore, by increasing the thickness of the slabs and their dimensions, the stresses caused by the temperature are increased while the stresses caused by the wheels are decreased.

The sustainable development indicators can be investigated in three groups: Social, Economical and Environmental. Development of the cities is one of the indicators of the progressive trend and it has resulted in extension of urban and interurban roads. As the Asphalt concrete is the main type of the road surface in the country, application of the cut back bitumens is always of the environmental concerns. The bitumen emulsion is considered as the replacement for the cut back bitumen. In this paper, the sustainable development parameters are defined and the economical impacts of the bitumen emulsion application is investigated. Then the cost of performing Two-layer Surface Asphalt using bitumen emulsion and cut back bitumen is calculated based on the basic unit price list for roads, railway and runway and finally the results of analysis are presented.

This study aims to evaluate intermodal seamless transportation system in Tehran's subway (case study: SADEGHIYEH station) through prioritise existing transportation alternatives (feeder modes) and assesing and comparing the current situation according to these priorities. Therefore, two perspectives exist. First, this study applied Analytic Hierarchy Process (AHP) based on relevant expert’s opinions in order to assess and prioritize intermodal seamless transportation system from a policy planner’s perspective to find an improvement strategy. To achieve this purpose, the effective criteria through the literature review identified then main criteria have been revised. In addition, weights of criteria are calculated and then the piority of each alternative is determined and the results have been analyzed. The results indicate that the bus has the highest priority among the alternatives being discussed and vans & taxis, bikes & walking are the next rank. The results of the sensivity analysis shows that change in weight of the three cases of the criteria can cause changes in prioritizing alternatives. Second, regarding the passenger’s perspectives based on relevant passenger’s opinions, most passengers tend to use bus and vans & taxis, bikes & walking was found to be less preferable than other alternatives. Finally, comparing the results of two perspectives indicates performance of the system in current situation is good and appropriate.

One of the most important infrastructures of the country is the production of quality materials for construction operations. Improper use of materials in the process of asphalt construction, causes rapid destruction, shortening the pavement life and causing a lot of damage. This phenomenon causes a lot of costs to bring the pavement to acceptable quality. Given that gradation accounts for a large part of the volume of asphalt pavements, it is obvious that this part has a significant impact on the behavior and performance of pavement. Improper gradation use for asphalt pavements causes numerous failures including rutting and fatigue cracks. The route of Azadshahr-Mino Dasht is one of the busiest roads in the country, which has suffered from rutting breakdowns and numerous fatigue cracks. The present study investigates the causes of these failures and finally offers solutions to eliminate these failures.