پژوهشنامه حمل و نقل
سال چهاردهم شماره 4 (پیاپی 53، زمستان 1396)

Globalization and competitiveness and their effort on outsourcing approach of an organization have involved it to consider purchasing role and its performance in supply chains as an important issue. Regarding JIT purchasing advantages in manufacturing industries, there is a growing trend toward JIT purchasing in research studies. Due to inventory and its related costs especially in textile and clothing industries, traditional procurement and production systems lead to unprofitability. Therefore, JIT logistics and purchasing have an important role in these industries. In this paper, we propose a conceptual model for JIT purchasing in a clothing supply chain. Via generalizing items and supplier classification strategies under Just-In-Time network, a freight consolidation model for gathering items based upon logistics costs is developed. An efficient algorithm for freight consolidation policy in the clothing supply chain is implemented. Finally, an illustrative example is used to show the model applicability and logistics cost efficiency of approach.

Nowadays, transportation planners are more engaged in effects of transportation on economic as a term of sustainable transportation. Sustainable transportation is an approach to organize principle for sustaining finite transportation resources necessary to provide for the needs of future generations considering economic, social and environmental terms. This paper is focused on the economic term of sustainable transportation through transportation cost and revenues for people as well as for the system operator. An algorithm is offered based on a method to determine provincial economic sustainability index of transportation using factor analysis through SPSS. As an example the algorithm is adopted for analyzing the economic status of sustainable transportation of the U.S. states. Results show that, according to the developed methodology, District of Colombia, Nebraska and Kansas are the most sustainable states while Alaska, Maryland and New Hampshire are the lowest ones regarding the economic term.

Black spot identification is one of the major issues in the context of traffic safety. So far, various methods have been used in relation to this matter. In this study, we use a hybrid method of data envelopment analysis and analytic hierarchy process (AHP/DEA) as a suitable method to identify black spot location that which was not used previously in this context. AHP method has the disadvantage that it requires expert weighting and the main weakness of DEA is inability to prioritize decision units. Therefore, combining these two methods in this paper we have tried to overcome the weaknesses of both approaches. The presented methodology in this study was applied on the 51 sections of two-lane two-way rural roads. The results of our methodology were compared with results of other methods of identifying black spot locations. These comparisons verify the results of our work and show the power of AHP/DEA in identifying black spot locations.

Vehicle demand forecasting are particularly challenging in Iran because seldom researchers worked on this topic. While most of researchers in Iran studied forecasting models of passenger cars, this paper investigated commercial vehicles which have hardly been addressed in the literature. This paper forecasted demand functions of Iran commercial vehicle in different segments (pickup, transportation vehicles and wide range of truck) via econometrics methods stock adjustment models. Also, since commercial vehicle demand is a derivative one, related variable of each passenger and cargo transportation is considered in the developed model. The results illustrate that in all estimated demand models, price and inventory are seen as effective variables. In bus segment, population is a substitute and effective variable, although service values added as well as cargo are known as effective variables in pickup and truck segments.

Locating and height of waterways are critical factors in road designing. In mountainous areas due to the existence of sufficient slope, locating and capacity of culverts can be calculated based on the upstream watershed inflow and analytical studies for various flood return periods. While the waterway Locations and road heights in areas with flat topography are not simply possible because there are no height differences significantly on both sides of the road. In flooded times, water level behind the road begins to rise and submerges a huge area. In this case, calculating the appropriate height for road and waterways capacity to prevent overtopping is very important. Due to the nature of the flow in these areas, two-dimensional flow modeling for determination the flooding surface and water level is essential.In this paper, for case study, part of the main road Lamrd- khonj located in Fars province and near the Lamerd city is studied. Initially the flood discharge with different return period is determined by hydrological studies, then the flow behind the road is simulated with a 2D hydraulic numerical model. According to the obtained results, the dominant flow direction, possible overtopping areas, flooded surface and water level behind the road are determined. The results of model are considerably in good agreement with the traces left by the recent floods. These studies can be applied as a suitable guide for present and future roads in flat areas which are endangered by floods.

The train scheduling is one of the most important problems in transportation planning. This problem aims to generate a feasible train timetable subject to operational constraints. Furthermore, optimal utilization of locomotives should be considered in rail transportation planning. In this paper, a new mathematical model is proposed for train scheduling and locomotive assignment. In this model, the train scheduling problem is modeled using the job shop scheduling problem with the total length of schedule or makespan minimization as the objective function. Then, locomotive minimization is added to the model as the second objective. The obtained bi-objective model is analyzed by benefiting Pareto frontier method. Numerical examples are illustrated to prove the model efficiency.

Revenue management is a set of methods and techniques are implemented to maximize revenue of selling perishable goods. Flight tickets are worthless after departure so they are kind of perishable goods. Dynamic models are one of the most popular revenue management models which provide optimal sale policy considering demand forecasting. Because of uncertainty of demand forecasting, there are some amounts of risk in using revenue management methods. In this research, a dynamic model of revenue management has been offered which provides facility of choosing risk level for decision maker. According to results of computer simulation experiments by considering of batch booking, Sharpe Ratio values which express rate of efficiency on risk are calculated for various risk levels and an optimal risk level has been suggested. Tables of sale policy for risk neutral policy and optimal policy are provided and compared. Problem has been solved for assumption of 'no batch booking' and finally effect of batch booking assumption has been checked on expected revenue and optimal risk level.

Resistive Economy is a well-known phrase for the nation who always is under pressure and economic sanctions of unreasonable and devouring countries to weaken their spirit and make them to give up resistance against enemy's unreasonable wills. Resistive Economy is so essential for our dear country which was accented by the Leader of the Islamic Revolution so many times as a vital way to exit cruel enemy's economic sanctions. This is so important that slogan of the recent years were selected mostly in economic bases and the solar year of 1395 and 1396 has been named 'Resistive Economy, Practical Steps and Action' and 'Resistance Economy, Production and Employment' respectively. by the supreme leader which has to be practiced by ministries and government to be used as a road map of all government economic plans. In this study, efficiency of Ministry of Roads and Urban Development actions on implementation of Resistive Economy with reliance on reducing costs and improving efficiency in transportation sections has been analyzed. The huge part of development budget and most of country's energy consumption have been managed by this ministry so that reducing costs and prioritizing the important actions of the ministry is a big step toward the country and Resistive Economy goals. According to the results, Ministry of Roads and Urban Development actions in transportation sections with Resistive Economy indexes by using TOPSIS method are ranked respectively as follows: transportation fleet, railroad transportation, road transportation, marine transportation, ports and border terminals, and aviation. According to the data of the Ministry of Roads and Urban Development, the Department of Rail Transportation ministry's plans to rank with the results of this study do not adapt.

This paper investigates the effect of recycling of steel slag aggregates (SSA) and reclaimed asphalt pavement (RAP) on the rutting properties of the warm mix asphalt. Nine types of asphalt mix with different combination of SSA and RAP were prepared and underwent static and dynamic creep tests as well as strength deformation test developed by Kim et al. Results showed that the inclusion of SSA into the asphalt mixes improves the rutting resistance; however, the improvements were insignificant in statistical point of view. In contrast, the effect of incorporation of RAP found to be significant by all rutting criteria. However, the mix with 40% coarse SSA and 40% fine SSA had the best rutting performance with 18.3, 36.2, 11.6, and 13.8 percent improvements in rutting criteria in static creep at 100 kPa, static creep at 150 kPa, dynamic creep and Kim tests, respectively. Statistical analysis showed that the dynamic creep and Kim tests had the best reproducibility potential as they offered lower coefficient of variation than other tests. Moreover, results signified that the static creep test at 100 kPa led to poor results in ranking the mixes and had weak correlation with other tests. On the contrary, static creep test at 150 kPa and Kim test exhibited good correlation with dynamic creep test and the ranking of the mixes in these test were consistent.

The aim of this study is feasibility of using Coal Waste Ash (CWA) as partial replacement of cement in non-air entrained Roller Compacted Concrete Pavement (RCCP) and evaluating its durability against deicing salts effect. In this research, 4 different mix designs were used to prepare RCC samples. The cement content equivalent to 14% by mass of dry materials was selected for control mixture without CWA. In other mixture, 2, 3 and 4% (by mass of dry materials) CWA was used. In order to evaluation the durability, chloride ion penetration, deicing salt surface scaling resistance and freeze-thaw resistance exposed to salt solution were performed. According to results, all mixture in this research obtained acceptable chloride ion penetration. The mixture with 3 and 4% CWA showed the highest and lowest chloride ion resistance respectively. By increasing CWA contents to amount of 3%, surface scaling exposed to salt solution in RCC samples delayed approximately 5 cycles. However, start of surface scaling in mixture containing 4 % CWA occurs in lower cycles compare to other sample. At the end of surface scaling test, weight changes in samples containing 2 or 3% CWA is almost the same as controls mixture. Up to 180 freeze-thaw cycles in presence of salt solution, ultrasonic pulse velocity in control mixture is higher compare to other sample. While, the reduction of this parameter is lowest for 3% CWA samples at the end of the freeze-thaw test. Based on ultrasonic pulse velocity during 300 freeze-thaw cycles, control, 2 and 3% CWA samples have excellent resistance. Mixture containing 4% CWA have excellent resistance during 180 freeze-thaw cycles. However its resistance decreased in continues. Relative dynamic modulus of elasticity during 300 freeze-thaw cycles is almost the same for control, 2 and 3% CWA samples. While this parameter for mixture containing 4% CWA reduced more than 40% at the end of freeze-thaw cycles. The durability factor at the end of freeze-thaw test, are satisfactory for control mixture and samples containing 2 and 3% CWA.

Fastening systems, as one of the main components of railway superstructure, play an important role in providing the safety of railway tracks. Nowadays, the performance of railway tracks in design and construction of new lines by using the different types of fastening systems have been increased. According to the variety of fastening systems, their performance should be evaluated. In elastic fastening systems, the deformation of fastener due to the moving trains returns to its original state after unloading. Therefore, the elastic behavior of these fasteners provides the better performance for railway tracks which this issue causes to use these elastic fasteners in high speed and heavy-haul railway tracks. In this paper, in order to investigation on the performance of railway fastening systems and their creep deformations, the rail creep resistance has been investigated by implementing the fastening longitudinal resistance tests. Rail creep resistance is the movement of rail rather than sleeper under the longitudinal loading. For this purpose after creating a rigid support for sleeper, rail was loaded in its direction and the longitudinal force-displacement values have been recorded. In this paper, fastening longitudinal resistance tests have been implemented on the different fasteners including Pandrol e-Clip, Vossloh, K and KS in same conditions. Based on the obtained results, the Pandrol e-Clip fastener has had the most longitudinal restraint and the least residual strain and also the rigid fastener of K has shown the most residual deformation.

Nowadays, by increasing of the load and volume of traffic passing through asphalt pavements, increase in the durability and resistance of these types of mixtures have become more of interest to researchers. Using appropriate filler is of the factors affecting the quality of asphalt production. Although low amounts of fillers are used for preparing asphalt mixtures, their significant influence has become specified and wide researches have been performed on this subject. As the fine part, filler has an effective role on the mechanical and behavioral properties of asphalt mixture and influences the interlock of materials, intensively. Some results indicate that most of biomass ashes are of various elements that are useful for asphalt. Rice husk ash, which is considered as a biomass ash, is one of the waste products obtained from furnaces at power plants, which is obtained due to the burning of rice husk. Currently, rice husk ash is widely used due to its beneficial properties in the concrete production industry. In this research, rice husk ash was used as a replacement for a part of filler (rock powder) in hot mix asphalt. First, Marshall Samples were prepared to determine the optimum bitumen content based on grading No. 4 and 5 in the percentages of 0, 25, 50, 75 and 100 of rice husk ash, as the replacement of the rock powder. Then, new samples with optimum bitumen content were obtained and prepared according to the previous gradation. Finally, the effect of using rice husk ash on rutting phenomena, moisture sensitivity and resilient modulus of hot mix asphalt was investigated. The results showed that using this additive by an optimum extent improves the asphalt performance, significantly.

Pavement maintenance and rehabilitation is of great importance in increasing the lifetime of the roads which requires a huge finance. Through a pavement management system (PMS), these actions can be proioritized with optimized financial costs. In order to establish such situation, a database is required to investigate gathered information in different periods. As the establishment of PMS in Iran is in the beginning stages and there is no access to a long-term database, planning and proioritization of road maintenance can be effective and operational, considering the current condition of pavements’ defects. In this paper, the surface condition of about 800 km of arterial road network in Kermanshah province is evaluated based on International Roughness Index (IRI) and Pavement Surface Evaluation and Rating (PASER). In fact, this paper proposes the maintenance options required for each section based on the pavement condition through the aforesaid indices and their combination. Reviewing the data and their results show that the high intensity of surface roughness (high IRI) does not necessarily mean the existance of surface defects with high intensity (low PASER), and vice versa. Therefore, the combination of these two indices can have more appropriate performance than each of them to show the pavement condition. A regression model is introduced to create a relationship between IRI and PASER which expresses the capability of proper estimation of each index according to the other one.

According to current statistics, more than 12 million tire rings (250 thousand tons) are consumed annually in Iran. The use of worn tires in the construction of a new category that has attracted the attention of experts and numerous studies has been done in this regard. Bitumen obtained from crude oil or bitumen, which has long been used for many years as a binding agent in road construction or other insulation and coatings, it has never been quite satisfactory from a set of physical and mechanical properties, due to its limited physical and mechanical properties, and it has limited operational capability and service time. Therefore, researchers have always tried to change the properties of this heaviest cutting oil in the desired direction. Improvement of the properties of the bitumen will increase its quality and increase the service life and hence the cost of maintaining and replenishing the coating will be diminished in such a way. One of these modifying materials is the use of rubber powder. In this research, rubber powder is used to recycle asphalt tiles. The results of the experiments show that this asphalt has a Marshall resistance compared to conventional asphalt, with a higher modulus of tensile and indirect tensile strength and less rupture depth.