پژوهشنامه حمل و نقل
سال هفدهم شماره 4 (پیاپی 65، زمستان 1399)

Asphalt mixtures with aggregate or stone mastic asphalt (SMA) are among the hot asphalt mixtures that have been used in different countries due to their special characteristics and in order to increase the load-bearing capacity of pavements and increase their surface friction. Excessive use of bitumen in these mixtures forms a relatively thick membrane of bitumen on aggregates, and creates special properties for these mixtures compared to asphalt concrete mixtures. Various methods have been used to strengthen of the asphalt mixture, such as the use of various additives. Rice Husk Ash (RHA) filler is one of the additives that has been proposed to improve the connection between asphalt bonding and materials used in addition to the environmental aspect. For this purpose, in this paper, a total of nine types of SMA in different percentages of bitumen 60/70 and with the percentage of replacement of filler stone materials with 0%, 25%, 50%, 75% and 100% filler of RHA, and experiment Marshall were done on them. The results of mechanical properties showed that the addition of rice husk filler improved the adhesion between bitumen and aggregates and increased the rutting resistance of SMA by increasing the Marshall Ratio. Increased unit weight and percentage of space filled with bitumen due to the increase in the thickness of the bituminous membrane around the aggregates and due to the presence of rice husk filler were other results of this study. Finally, it was concluded that the replacement of aggregates filler with RHA filler in different percentages and 6.5% bitumen resulted in better result.

The purpose of this paper is to investigate the effect of rubber powder and Gilsonite powder on the rheological properties of bitumen. In this study, the gilsonite powder was used as additive in percentages (0 %, 10 %, 20 %, 30 % and 40 %)in bitumen. Also, in order to limit the degree of penetration to 30 - deci mm at 25 C, the Gilsonite percentage is considered to be 30 % fixed and the percentages of rubber powder are considered to be 30 %, 10 %, 15 %, 20 %). In order to investigate the performance characteristics of bitumen, the penetration, softening point, ductility, dynamic shear rheometer, bending beam rheometer, rotational viscosity, multiple stress creep recovery (MSCR) tests were performed. Results showed that the G */ Sind parameter increases with addition to gilsonite. Also, rubber powder causes an increase in the value of G * / Sind parameter and the rutting parameter increases by addition of crumb rubber percentage. The addition of gilsonite powder causes an increase in values of G *. Sind and adding crumb rubber powder cause a decrease in values of G *Sin d. it is found that the parameter (Jnr) decreases with addition of gilsonite and rubber powder. The lower values (Jnr) indicates the further resistance of the mixture made with the bitumen or less rutting sensitivity. The results show better values for rubber powder additive compared to Gilsonite.

Rail transit plays an increasingly important role in the public transportation system, and effectively reducing its huge energy consumption is of great practical significance. Wider use of public transport, particularly rail and metro, is one way to save energy. A growing trend of applying the rail network and metro by governments on one hand and the considerable energy consumption of a train during one year, on the other hand, demonstrate the necessity of considering the consumed energy by train. Railway transportation consumes amounts of energy. Direct energy consumption to complete the transport tasks is the main part of energy consumption of rail transportation, especially the traction system, which leads to the railway transportation costly. Optimization of the train speed curve plays an important role in minimizing train energy consumption. In this paper, first, there was a review on models of train energy optimization with different characteristics and corresponding other algorithms to find the optimum speed profile and accuracy of them, Second Tabu Search (TS) algorithm as a new approach for optimizing the train speed profile to save energy will be investigated. In this approach, after determining the appropriate points of acceleration, neural and braking, a speed profile in which train could cover its route with minimum energy consumption will be achieved. We call these points "the variables for changing the training strategy. The algorithm was implemented in alternative routes. In this study, the simulations of the proposed method are implemented in MATLAB software and are finally compared with the Genetic Algorithm method.

As SBS modified asphalt has the disadvantages of high initial cost, difficult processing and poor storage stability, many researches have been conducted experiments on composed modified asphalt to get a more satisfactory pavement performance. This study proposed an asphalt mixture modified by nanosilica, rock asphalt and SBS. Basic performance tests of asphalt, rutting tests, low-temperature bending tests, moisture susceptibility tests, fatigue tests and durability tests of asphalt mixtures modified by SBS, rock asphalt, nano-silica/rock asphalt and nano-silica/rock asphalt/SBS were performed to evaluate their pavement performance. Comparing these tests results with the properties of unmodified asphalt mixture, nano-silica and rock asphalt cause an improvement in pavement performance. Nano-silica/rock asphalt/SBS modified asphalt mixture had higher temperature stability, low-temperature cracking resistance, moisture susceptibility and durability than 5% SBS modified asphalt except the similar fatigue life. Furthermore, economic analysis indicated that the nano-silica/rock asphalt/SBS modified asphalt mixture had higher cost effectiveness.

Rapid growth of population in metropolitan areas has led to an increase in transportation demand. Accordingly, development of transportation infrastructures is a necessity in management of urban transportation networks. Economic analysis of multiple projects is a major step toward achieving this goal. In order to evaluate the effects of network development plans, especially for the expressways and their interchanges, macroscopic traffic modeling software is usually applied. The software is capable of anticipating the traffic flow distribution in large scale networks and has acceptable accuracy according to their mathematical modeling approach. Also known as static tools, these software encounter severe level of errors in forecasting the traffic situations in small scale areas where interactions between traffic flows exist. Hence, using these tools to evaluate the plans of expanding the expressway network may lead to select a project which would not generate the expected benefits if implemented. In this paper, a hybrid modeling approach based on macroscopic and microscopic paradigms is proposed to verify the results of static software. In order to assess the proposed method, a real case design for completing the interchanges of an intersection between two major expressways in Tehran is studied. It is shown that applying the hybrid scheme is a necessity to guarantee the success of projects due to the characteristics of static software.

Many factors or parameters influence the field density of asphalt mixes. Since the number of variables affecting a large and somewhat different compacts affects each other, it is almost impossible to determine a constant interpolation relationship. Data mining and its techniques are a way of discovering hidden knowledge between dependent and independent variables, as well as indirect and nonlinear relationships can be identified by dividing the data into groups or leaves in the decision tree method. In this study, commonly used data mining techniques in civil engineering, including the neural network, logistic regression and decision tree. By emphasizing the application of decision tree method, with the aim of exploring knowledge models and providing predictions, other data mining tools are used to assist in constructing and evaluating the developed satistical model. The explanatory variables used in the three models of this study are the percentage of void, asphalt mix strength, aggregate size, bitumen percentage, asphalt mix flow. The results show that the percentage of void content of stone materials, the percentage of passage of sieve 200 and 4, and the bitumen percentage had a greater effect on the density and compaction of asphalt mixture. Also, a multiple linear regression model with a correlation coefficient of nearly one between the density of asphalt mixture and variables were presented.

Road traffic crashes are one of the major causes of deaths and injuries around the world. Approximately 1.2 million people (2.1% of all deaths) are killed every year and over 50 million are injured or disabled worldwide due to road traffic crashes. To control speeding and deaths different approaches regarding the road function has been proposed already. Speed cameras are one of these options in use. It has been approved that they are effective in reducing speed and crashes near speed cameras locations. This Study aims at evaluating the highways speed cameras through the Naïve and Naïve adjustment method in city of Mashhad. In this study Mashhad highway network was evaluated by before and after study and speed cameras crash modification factor was calculated for the first time for these cameras. This study revealed that these cameras are most effective in reducing invulnerable crashes however they are effective in reducing vulnerable crashes.

Nowadays traffic congestion in metropolitan areas like Tehran has become a critical issue requiring transportation demand management policies as solutions to reduce demand and maximize facilities efficiency. An effective transportation management measure is congestion pricing, which needs special attention to be performed successfully because of its low public acceptance. In this study, based on the data gathered from 455 face-to-face questionnaires through a surveys conducted at restricted traffic areas of Tehran in 2018, we analyze latent factors affecting acceptance of Tehran peak-based scheme. Exploratory factor analysis and ordinal logit models are used for our purpose. Results show that attitudinal factors like perceived effectiveness of the scheme, officials’ performance, scheme design and the way it is performed and environmental concerns besides some socioeconomic factors like education, car ownership and travel patterns are among the most effective items. Results also show that congestion pricing acceptability among people with more information about this program is more, and less for regular users of restricted traffic areas. This research can assist transportation decision makers in taking appropriate measures and policies with maximum acceptance level.

Exchange rate fluctuations and the resulting uncertainty are one of the most important macroeconomic variables that affect different sectors of the economy in various ways. Given that these fluctuations do not have the same effect on economic sectors, Therefore, in this study, the uncertainty effects of exchange rate on the growth of road transport sector during the period of 1368-97 have been investigated. The aim of this study is to investigate the effects of exchange rate changes on the growth of the country's road transport sector. For this purpose, the EGARCH model has been used to calculate exchange rate changes. In addition, the self-regression model with distributive interruptions has been used to estimate the main model. The results show that exchange rate uncertainty has a negative and significant effect on the economic growth of the road transport sector, both in the short and long term. Also, the results of the error correction coefficient show that the adjustment speed of the model is slow. The error correction model is only able to explain 434% of exchange rate fluctuations.

The study of the effect of transportation price on the price index of economic sectors and the place of transportation according to the forward linkage, backward linkage, Power of Dispersion Index and Dispersion Sensitivity are considered as an important topic. In this way, this paper first examines the place of transportation in the Iranian economy and then examines the direct effects of increasing the price of transportation on the price of different economic sectors. To do this, using the Input-Output analysis and table 2011 of the Statistical Center of Iran. First, the symmetric table is calculated for the constant price and then merged under the various economic sectors and the input-output table is considered as 25 sectors. According to the results of this study, the highest impact of an increase 20%, 30% and 40% in transportation prices on commerce and hotel, petroleum products, chemical products, and mineral industries, agriculture and animal product price index.

Scour at the shallow abutment foundation during floods is a common cause of bridge failure. In some cases, the bed is reinforced with riprap. There are several advantages and disadvantages of using this method. One of the disadvantages of using flush riprap aprons with the bed is that heterogeneous roughness (riprap versus native bed materials) alters the flow and manifesting as strong secondary currents. This flow can increase the shear stress and the scour depth in the unprotected bed. To study the subject, a conceptual model for determining the shear stress ratio in the unprotected bed in both with and without riprap has been investigated. In developing the conceptual model, numerical simulation tests in a flexible bed have been used. Then, the validation of Flow3D numerical model is presented and the mentioned model is used to simulate the flow in two cases with and without riprap in the rigid bed. In a rigid bed compare to flexible bed, computational and hardware costs are significantly reduced. The shear stress ratio in the unprotected bed is calculated and the quadratic polynomial equation is fitted for different roughness ratios. The coefficient of determination in each case indicates the appropriate correlation of the stress ratio in the two modes of flexible and rigid bed.

Revenue risk sharing is a challenging issue in PPP highway projects that can be addressed by the options theory. The objective of this study is going beyond the common standard options by suggesting a set of exotic options suitable in modeling the revenue risk sharing mechanisms of PPP highway projects, and proposing evaluation and comparison techniques of these mechanisms. First, a series of semi-structured interviews are conducted to collect the experts’ judgments on the implication of each exotic option for the revenue risk sharing mechanisms of PPP highway projects. Then, through a content analysis of the interviews, the applications of these exotic options in the context of highway projects are identified and their risk sharing mechanisms are designed. The Geometric Brownian Motion and the Monte Carlo simulation are employed for forecasting the revenues and payment valuation of the options during the operation of highway projects. The application of the proposed mechanisms is tested in a real BOT highway project. The developed mechanisms and their quantitative evaluation techniques demonstrate their efficacy in supporting both public and private stakeholders of PPP highway projects in revenue risk sharing by (a) designing revenue risk sharing mechanisms, (b) simulating future revenues, (c) calculating the ultimate payment of options-based revenue risk sharing mechanisms, and (d) evaluating the risk spectrums of stakeholders with diverse risk appetite tendencies. Lastly, this study represents how exotic options can enhance the capability, flexibility, and precision, of revenue risk sharing mechanisms of PPP highway projects which can guide both parties to a win-win situation through a revenue risk sharing structure that considers their requirements and strategies.

However, the land transportation of dangerous goods via rail or road plays an effective role in development of business transactions and meeting the industrial requirements, it has a potential danger to the human life and property as well as the environment health. Therefore, the national and international regulations have passed specific requirements for the persons involved in transportation of such goods in order to prevent any incident and minimize the respective effects. In addition, some of the requirements have a contractual source which is imposed on the carrier in order to provide the utmost private and public interest. The carrier of dangerous goods is one of the parties to the transportation contract who plays an important role in monitoring the dangers resulted from transportation of such goods. The present research with a descriptive-analytic method intends to explain all the exclusive duties of the dangerous goods carrier by taking into consideration the contract of carriage and the international regulations governing the land transportation in comparison with those of in Iran. The conclusion of the research shows that the carrier who is aware of the dangerous nature of the goods is required to take the utmost care of the safety of the transportation process in order to prevent damage and protect the public interest. He/She has to take the utmost care in employing the experienced and trained staff, carrying out proper load, stowage and unloads, using vehicle appropriate for carriage of dangerous goods and checking the appearance of the cargo. However, in some regulations, it is not enough to take the utmost care for using the appropriate vehicle but the carrier shall provide the real and unavoidable proof in order to relieve of liability.

Although one of the successful modifications for pavement asphalts was the blending of asphalt and the recycled crumb rubber using conventional wet process, problems with asphalt rubber, such as phase separation and weakness in workability, led to the introduction of the terminal blend process (TB) for the proper blending of asphalt and rubber. During terminal blending process, rubber particles are completely digested in asphalt binder which could cause weakness at high temperature and a reduction in viscosity of TB rubberized asphalt compared to conventional asphalt rubber. In order to reduce the problems of TB rubberized asphalt, its modification is necessary. The main aim of this paper is to modify the TB rubberised asphalt by adding 2% and 4% nanoclay. First, after preparation of seven asphalt samples, the prepared nanocomposite structure was analysed using XRD and SEM tests. Then, the TB rubberised asphalt nanocomposite ageing, rheological, and physical specifications were investigated. The results showed that modification of TB rubberised asphalt by nanoclay reduced the temperature susceptibility and phase separation of it. On the other hand, it has been shown, compared to TB rubberised asphalt, TB rubberised asphalt nanocomposite has a high viscosity, softening point, and ageing resistance and also improved performance high temperatures.

Following the increase in population and the urbanization, there is a need for a public transportation system to facilitate the movement of citizens and access to their activities and services. One of the main types of public transport systems is the metro that has an effective role in reducing traffic flow of cities. So, suitable location of metro stations with regard to the surrounding environment can play an important role in increasing the efficiency and performance of the metro system. The purpose of this paper is a comparative analysis of Imam-Hossein and Jaber-Ansari metro stations in Isfahan and the quality of their surroundings. In this regard, the required information was collected through documentary and field studies (observational, questionnaire and interview). Also, for this purpose, random sampling method was used with unlimited statistical population and 122 questionnaires were distributed. In order to analyze the components and measures, one-sample T-test and Mann-Whitney-U test in SPSS software were used. As well, we used Analytic Hierarchy Process (AHP) method through Expert Choice software in order to determine the weight of the factors and measures. The results indicate that in general, Imam-Hossein station is in better condition than the station Jaber-Ansari based on the factors and related measures of security, justice, safety, economic dynamism, social dynamics, user and access, as well as the importance of each of them. These findings are mainly due to the location of Imam-Hossein station in one of the most important and lively centers of the city and the location of Jaber-Ansari station in a residential neighborhood.

One of the important lateral forces is dynamic loading due to earthquake. The behavior of pile foundations under earthquake loading is an important issue that widely affects the performance of structures. The topic of seismic pile behavior has been covered extensively in the literature over the past few decades. In this paper the behavior of single pile and pile group have been examined. Pile group has four piles and rebar and concrete weight in pile group is equal to single pile in this research. The single pile and pile group are analyzed under Tabas, Bam and Loma-perita earthquakes loading. The finite element software, ABAQUS, is utilized to model pile and piles group. Soil is modeled as an elastic-perfectly plastic model using the Mohr–Coulomb constitutive model. The side boundaries are constrained against horizontal direction and the bottom boundaries are constrained against both horizontal and vertical directions. Maximum shear force, lateral displacement and force along the pile in single pile and pile group, under the earthquake loading that mentioned above, have been measured. The results are shown the settlement in pile group is around 30 percent less than single pile and the lateral displacement in the head of single pile is 0.23 meter but the lateral displacement in group pile is 0.1 meter in Bam earthquake loading. The shear force in the head of single pile is 2084 kN and the shear force in head of the pile in pile group is 334 KN. Taking into account soil condition, the results shown that utilize the pile group (equal rebar and concrete weight by single pile) is better and more economic than single pile.

In this research, the duration and appropriate time of walking to reach the routine destinations and meet the needs of individuals based on the different criteria of city districts and neighborhoods including individual, social, economic, and physical ones as well as land uses. The results can evaluate challenges and deficiencies based on the affecting indicators in different regions, and finally, they can lead to the adoption of measures and propositions so that people can fulfill their purposes and needs by walking over a proper time. The analysis method performed here was to by using statistical regression modelling. To reach the goal of this study, first, the city of Gorgan, Golestan province, Iran, was introduced, then, the land use map and land use distribution diagram by neighborhood were given, and next, the demography of the respondents to the questionnaire was investigated. Finally, four modelling types were addressed to measure the walking time for different purposes; 1) occupational, 2) educational, 3) shopping, and 4) recreational. By investigating the results of walking time models in different districts of Gorgan and by considering the t-test coefficients and Watson coefficient, being 1.5-2.5 for all the models which is acceptable, the independent variables of the area and concentration of office land uses, age, and car ownership (to measure the walking time of occupational travels), the independent variables of the area of educational land uses, income, and age (to measure the walking time of educational travels), the independent variables of the area and concentration of service land uses, age, and car ownership (to measure the walking time of shopping travels), the area of greenbelts and parks, and different variables of the area of sporting  land uses, car ownership, and age (to measure the walking time of recreational travels) were determined to be significant. At last, tables showing the coefficients of independent variables and the constant of the prediction model for the walking time of each type of travel were presented.