فصلنامه مهندسی حمل و نقل
سال هفتم شماره 4 (پیاپی 28، تابستان 1395)

Car accidents are undesirable and inevitable event in traffic flow, causing loss of wealth and human life. Research has shown that is a relationship between the pavement condition and crashes. Characteristics of pavement failure such as depth of failure and its area is one of important and impressive parameters on the behavior of drivers. This study investigates the influence of pavement failure of urban road and traffic condition on the crash. Since pavement roughness has a significant impact on road accident, it is necessary to be considered in road safety planning and improving pavement condition. In case of failure of pavement bumps and falling surface of pavement was studied. 18 data points were measured on deteriorated pavement and response and 30 drivers speed that faced with the failure were recorded. To determine the factors affecting the amount of traffic diversion, the decision tree method was used. Decision tree for a graphical representation of the results is easy to understand and interpret. In this study, the data decision tree was constructed by Classification and Regression Trees (CRT) algorithm. The tree shows the variables such as area, Length and width of pavement roughness compared to value of traffic, speed, failure center distance to the right side lane and kind of roughness (bump and sag) has greatest effect on driver direction change.

Pedestrians especially in the developing countries are the most vulnerable groups in the traffic classifications. Among these group children for various reasons has a very serious condition. This topic has particular importance in Iran because of existence of roadside schools. In this study, at first the aspects of the conflict of crossing the street at an intercity roadside school are analyzed, by using videography. Then, using mathematical modeling and data mining from study variables and using statistical data from Students crossing the street, the conflict modeling and security risk modeling is completed. The results shows that 10 variables such as; The size of the passing group, the approaching speed, waiting time before crossing, stopping and waiting time on line, average passing time, average passing speed, give attention to the approaching vehicles, coming back from the path, how to cross, the marginal safety of roadside and vehicle type, affects on the students safety. Among these results, give attention to the approaching vehicles and waiting time before crossing, respectively has the most and the least effects on student choice of crossing.

Competitive environment has increased among Iranian and foreign carriers due to the recent changes in the field of pricing and foreign exchange rate. In addition, entry of new airlines including Low-Cost airlines can complicate competitive conditions more than before. Therefore, study of passenger's choice behavior and forecast market demand for air travels can improve planning process of airlines. For this purpose by using the stated preference statistics, the competition of Low-Cost Carriers in contrast to Full Service Carriers and based on the designed scenarios has been analyzed. Fractional factorial design technique has been used in order to design a basic mechanism for transferring information about the selection options, their attributes and each attribute level to passengers. Then, outgoing passengers who were traveling to the destinations of five south-east Asian countries were individually interviewed in Imam Khomeini (RA) International Airport and 480 questionnaires collected. The collected data were analyzed and investigated by using Multinomial Logit Model (MNL). The results indicate that ticket price and the variable of passenger's flight possibility on the desired day and hour for the Low-cost Carriers and the Full Service Carrier are quite different. The effect of these variables on passenger's category with business/non-business, the passengers who paid themselves for the tickets and others is statistically different. Also according to statistical results of model; gender, marital status, international travel experience and Membership of Flight Frequency programs (FFP) have been effective in selecting types of airlines. In addition, the rate of passenger's tendency to pay is different in various passenger's categories and in types of aviation companies.

Urban runoff are usually contains significant amounts of pollutants such as heavy metals and solid particles. High tendency to remain in the nature and accumulation in the food chain is the most important characteristics of heavy metals. There are many alternative management strategies available to treat these contaminants. Permeable pavement is one of the urban runoff management methods that in addition to reduce the risk of urban flooding will help to improve the runoff quality. The aim of this research was to investigate heavy metals and also suspended solids removal from runoff using slag, limestone and silica aggregates as filter and base layers of permeable pavement. All experiments were performed in cylindrical reactors with 0.6m height and 0.2m diameter. Each column was filed with a media depth of 0.5m (0.1 m for filter layer and 0.4 m for base layer). In order to determine the lifespan of the media synthetic runoff in successive cycles was continuously injected through the column. The results of this study showed that the base and the filter layers of the permeable pavement can reduce effectively the total range of runoff pollutants with high removal percentage. From three types of aggregates used as permeable pavement layers, slag material had better performance than the others. In this study the maximum removal of copper, zinc and suspended solids from runoff within 24 hours, were 61, 89 and 82 percent respectively, which increase to 72, 95 and 99 percent after 120 hours. The total capacity of slag aggregates for the removal of Cu, Zn and TSS were also estimated to be 28, 95 and 15485 mg/kg respectively. Based on the results, along with the slag, limestone showed a higher ability to remove pollutants from runoff as compared to silica.

Damage of flexible pavement due to cracking and rutting occurs. among these mechanisms, a lot of fatigue crack can be seen in asphalt surface, so many research has been done to improve the fatigue life of asphalt mixtures. The use of different materials in improving the behavior of bitumen characteristics is able to increase the life of asphalt pavement. Today, polymeric nanocomposites are one of the most popular of materials discovered recently and it can successfully improve properties if polymer is modified with small amount of nanomaterial on condition that the nanoparticle is dispersed at nanoscopic level. The tests on asphalt mixture modified by cloisite indicates that nanoclay modification can improve mechanical behavior properties of mixture, such as creep, indirect tensile strength. However, it has not mitigated the fatigue problem and hence, more research is required before it can be utilized on a large scale. In this paper, two types of montmorillonite nanoclay were used: Cloisite 15-A and Cloisite 30-B. For this purpose, control, 2, 4 and 6% of nanoclay mixtures were prepared. Then the fatigue behavior and resilient modulus test at medium and low temperature were evaluated. Four-point bending beam fatigue testing has been used for beam specimens under 10Hz loading frequency and test temperaturesbased on AASHTO T321 standard. Fatigue life, bending stiffness, dissipated energy and damage ratio were calculated using beam fatigue test results. At the end, it is concluded that both additive have great influence on improving fatigue behavior of asphalt mixtures at 25°C. In contrast, nanoclays don’t seem to have a beneficial effect on fatigue behavior at low temperature. Due to extremely high specific surface of nanomaterials, bitumen viscosity goes up and fatigue life will significantly improve. While at low temperatures, because of bitumen plastomer properties, we encounter with cracks problem and reduce in fatigue life.

Decision on policies such as the ban on vehicles traffic or on a specific day, parking charges and the possibility of variable work hours requires behavioral studies sensitive to this kind of policies which activity-based approach tries to create a suitable tool for with regard to time and space of people activities and their plan. Trip chain planning in such a way that people, especially in metropolitans, travel sequentially and without any need to return home is an attempt to save time and money, that this paper deals with mathematical modeling. Modeling the selection of trip chain pattern and interpretation of relevant variables are the main objective of the current paper which in order to implement the model empirically and quantitatively, data obtained from inquiry a sample of Qazvin residents (including personal and household characteristics) and the characteristics of transport networks and features of vulnerable sites for doing tasks is used. Selecting trip chain pattern of people with separated travel purpose is done by Multinomial Logit Model and factors affecting the selection of different types of trip chain pattern in three-trip tours is examined. The results show that the average travel time, passenger age, gender, car ownership, walking, business rates of one’s residential place, employment and per-capita vehicle ownership in the origin area are the various factors affecting the choice of the trip chain pattern. Such models and this analysis can help transport managers and policy makers in different management policies to improve traffic conditions by providing useful and needed information.

Taking the advantage of transportation services for employees corporate, offices and factories is one of the outstanding solutions to reduce traffic congestion and fuel consumption. In this way planning and allocation of vehicles to passengers and also determining the transportation routes are major problems. Such problems are known as Vehicle Routing Problem (VRP) that fall into category of complex multi-purpose optimization problem. This paper attempts to simplify the problem by breaking it into several simple and single-purpose problems and also to propose a novel approach for path finding. At first, VRP converts to several single-purpose problems, using improvement k-means algorithm. Then, a hybrid method based on Saving and Tabu Search algorithms is developed to find shortest path. Results show that hybrid method of Saving and Tabu Search algorithms is better and faster than using only Tabu. Keywords: Vehicle Routing Problems (VRP), Tabu Search Algorithm, Saving Algorithm, K-means Algorithm, GIS

In this paper, stripping phenomenon in hot mix asphalt in Iran has been studied. For this purpose the effect of lime and three types of liquid anti stripping agents on two types of stone materials, sensitive against stripping phenomenon, has been investigated. The liquid antistripping agent in this research has been selected from one of the most credited producers in this field and the dampness sensitivity of materials has been measured through AASHTO T 283. The economic evaluation has been done according to cost-benefit method for application of antistripping agents. The results show that using lime and anti-stripping agents, it would be possible to modify two types of materials which are sensitive against stripping. But it is required to study each material separately for evaluation of the effect of anti-stripping agents. The economic analysis is descriptive of the fact that in some projects, the application of anti-stripping agents results reduced costs, in addition to technical upgrading of materials quality.

Asphalt pavements are damaged continuously due to premature failures and exceeded traffic loads. Among the various failures, moisture damage is the most widely spread failure in asphalt pavements. Sulfur extended polymer is a newly developed additive that is used to increase loading capacity of asphalt pavement designed. However, the role of these additives are purely investigated in term of their effect on moisture resistance of asphalt mixes. In this research by replacing 30, 40 and 50 percent of Googas (a sulfur extended additive produced in Mashhad, Iran), Marshall size specimens were prepared. Modified Lattman testing was performed on mixes and their Tensile Strength Ratio (TSR) parameter was determined on all mixes. The results showed that above additive cannot attributed on moisture resistance of asphalt mixes as its present status. In order to overcome this lack of resistance, a crumb rubber modified containing 20 percent rubber was replaced with the original 60/70 pen bitumen of the mix. repeating all ITS testing on the above mix combination with this new binder, it resulted in improvement of mixes (about 15 percent increase in TSR value). This exceeded the minimum requirement of TSR for asphalt mixes which could not be achieved neither with conventional mix, nor with those containing Googas and 60/70 pen graded bitumen.