پژوهشنامه حمل و نقل
سال چهارم شماره 4 (پیاپی 13، زمستان 1386)

Electronic transportation marketplaces (ETMs) are Internet-based mechanisms that match buyers and sellers of transportation services. With claims of reducing the administrative costs of transportation procurement to virtually nothing, the allure of ETMs is considerable. Shippers (transportation buyers) must therefore determine whether to pursue the new-founded opportunity and buy transportation services through an Internet-based intermediary. To date, combinatorial auctions are increasingly used by large shippers as a method to establish service contracts with trucking companies. In order to achieve maximal benefits in these auctions, carriers must determine a bidding policy that can accurately evaluate the costs they will incur to fulfill these contracts and which can quickly examine many different possible options.In this paper a combinatorial double auction model to improve efficiency of trade in transportation electronic marketplace is presented. In this model both buyer (shipper) and seller (carriers) could bid combination of lane in the transportation electronic marketplace.First a framework is developed to show how combinatorial auctions are being used for the procurement of freight transportation services. Then the alternative solution is recommended, including a mathematical model. Also the result of mathematical model is analyzed and it is shown that in continuous mathematical model optimal solution is better than integer model in two aspects: marketplace benefits and time to solve the model.

The appropriate allocation of development budget for the safety upgrading of roads is one of the most specific safety management criteria in the roads. Determining the high risk areas and their prioritization for their accident probability is the fundamental step for planning of the roads safety.The determination of the risk of an area, is usually implemented by the investigating the frequency of accidents, rate of accidents, and the intensity of accidents. In this paper making use of Bayesian Theory, a method for determination of the risk in various points in a road and their prioritization is developed. In this method, on the basis of present information on accidents in one section, (which may be according to the engineering judgment or the statistics of accidents in the past years), the accident risk of the section is estimated and then by observation the real accidents occurred up to the end of the year, the risk rate of that section is estimated. Then these areas (which are similar to each other from traffic and geometrical points of view) are prioritized on the basis of their accident probability.One of the major factors in prediction of accidents in an accident prone section is the number of occurred accidents there. The greater the number of accidents compared to the traffic volume, the higher the number of risky factors. The second factor responsible for the accident probability of a section in the road is the intensity of accidents. The ratio of accidents which are ended to death toll, to the total number of accidents on that section is the intensity rate of accidents. Therefore in this research the accident prone areas are prioritized according to both parameters for their probability of accidents.The behavior of a section in the road for its accident proneness should be specified according to the distribution function of accidents there, to the traffic volume on that section. The higher the accuracy of fitting of a distribution functions on the accidents statistics, the more precise will be the prediction of accidents in the future. In this paper a model has been developed on the basis of Bayesian theory for determination of the risk rate of an area. The accuracy of the developed method comparing to other models is higher, in case of availability if some pert data in the study. By using this method it would be possible to determine the safety criteria for all the similar points through sampling of some points and studying their characteristics. Not to mention that the developed method, although is one of the statistical inference methods, but is sensitive towards its preliminary assumptions which are the former distribution function and the risk function. Due to sampling of similar areas, the Bayesian Method is more accurate for determination of the risk factor compared to classic methods.

In Iran, like many other countries the problem of traffic specially the density related issues is quite serious. Those organizations that are involved with the organization of transportation and traffic have recommended son many projects on the basis of Intelligent Transportation Systems to solve the related problems. But there has not been a comprehensive programme for implementation of intelligent systems. Lack of the strategic plans for intelligent systems not only causes double and repeated investments in infrastructure of the society but also brings about distortion and non coordination between these systems and may cause many problems when the subsystems should be connected to each other, thus results other problems for transportation system of the country.In this paper after literature review the various applications of Intelligent Transportation Systems were studied and then by using the methodology of strategic planning the strategies for intelligent transportation systems of the country have been provided. For provision for strategies the SWOT Matrix (Strengths, weaknesses, opportunities and threats) has been used. In order to prioritize the strategies the decision making techniques with Analytical Hierarchy Process (AHP) and Quantitative Strategic Planning Matrix (QSPM) were used and the resulted effects were then compared by Spearman ratio. Reviewing the results taken from the written strategies and the present circumstances of the country the following conclusion may be obtained:1-The situation of the country for development of the Intelligent Transportation Systems is generally not appropriate, regarded as medium for external factors, and weak for internal factors2-The development of Intelligent Transportation Systems in the country should be regarded with special emphasis on the safety of transportation systems and modes3-As the first priority, the prioritization of using intelligent transportation systems should be considered for accident prone areas, compared to highways and freeways4-In relation to large scale objectives of transportation systems as a whole, the following factors should be taken into account respectively: Safety, Public satisfaction, Improved environmental conditions, Reduction in energy consumption and mitigation of delay times5-Regarding the development issues, the considerable factors are respectively as follows: Management and organizational policies, Financing, Technical infrastructures, Cultural environment, Manpower and finally Legal issues. The development of Intelligent Transportation Systems should be implemented by such prioritizing 6-For the development of Intelligent Transportation Systems the skills and potentials of the private sector should be used and the governmental sectors are only responsible for policy making and provision of substructures for such development7-The required compatibilities and cooperation are not available between the responsible organizations and their situation and place of them is not specified8-The development of Intelligent Transportation Systems requires an organization with comprehensive structure and expertise manpower

Safety of roads is one of the most important aspects of traffic and transportation planning in the world. The high expenditures imposed to the societies due to accidents have made the safety of roads a very significant objective in traffic engineering issues. This paper studies the interaction between the pavement index of rural two lane roadways (the destruction of pavement, the skid effect and the road width) and the daily traffic volume effect on the rate of accidents and their prediction by multiple regression models. The results of this research show that:1. In rural two- lane roadways the skid coefficient is the most important factor in occurrence of accidents, in low traffic situations, while in high traffic hours the effect of road width is more significant. This issue may be interpreted in this way that in low traffic volume, the speed of vehicles is higher and thus the skid effect is more significant, while at the same time, in high traffic situations the vehicles are influenced by the speed of the adverse side vehicles and thus the width of the roadway becomes more important.2. Generally speaking, in rural two lane roadways, the skid reduction effect in reduction of accidents is more important in reduction of accident rate as compared to that of destruction of the roads pavements3. In two lane rural roadways, the road width is the most important variable after AADT (Average Daily Traffic) and the skid and then destruction of pavements are amongst the most important factors in accidents rate, accordingly.

Optimal allocation of resources for infrastructure facilities is a critical issue in planning of development activities. In Iran investment patterns and criteria under which resources are allocated among competing sectors and projects might have created investment bias towards already developed sectors, resulting in economic inefficiency. For this reason, the role of transportation investment on sub-sector economic development of Iran is examined in more detailed manner in this paper.Transportation is considered to be one of the most important infrastructural components influencing production. For this reason there exists considerable pressure for investment in the transportation sector. This paper argues TFP changes in the transportation and communication sector. According to the forth 5-year Development Plan in Iran, productivity is considered as one of the most important economic growth sources. Also, increasing in the productivity is required to improve by all public organizations and the ministries through the switching from input-oriented to output-oriented mechanism. In this context, it is needed to know the productivity increasing limitations in transportation and communication sector and how it is to be dealt with. To get this, in this study, TFP analysis is done by using DEA approach and Malmquist Index. DEA lends itself naturally to the performance of the economic sectors, because of its employment for assessing relative performance of sectors using various inputs to produce outputs. DEA is an ideal method to measure efficiency relative to the best performing sector. This allows us to identify efficient and non-efficient sectors and driving factors determining the efficiency of sectors. To do so, DEA calculates an efficiency score for each sector and generates the best practices frontier.The efficiencies are measured in terms of output productions, input factors and their weights, which are determined endogenously. The inputs include labor and capital consumption, and the outputs include value added production of each of the study sectors.At first, to identify the main resources of inefficiency for production factors in different economy sub-sectors, we measure relative efficiency. From figure 4, it is observed that in transportation sub-sector labor efficiency is decreasing during years after Islamic revolution in Iran. In data we find that TFP changes in the transportation and communication sector is the lowest in compare to the TFP for other economic sectors in Iran and also, this productivity growth was mainly accomplished through technical progress rather than efficiency improvement (table 2).But, according to the inter-sector TFP decomposition, problem in the management and technical efficiency causes decrease in the transportation and communication sector TFP during the period of study.To identify one of the main causes for this problem, we direct the readers to this fact that in Iran accessibility primarily depends on the roadway network. The negative externalities of the traffic jam, lack of facilities for alternative transportation modes (some because of sanction on air transportation) and its influence on efficiency is clearly demonstrated in the analysis.Public sector management in this sector can be mentioned as another source for management inefficiency which causes some problem for efficiency.It is also tried to investigate the reasons of this hierarchy of the transportation and communication sector concerning efficiency. As the inefficiency affects, the roles of monopolies in the sector, whole economy management, weak liberalization, the level and degree of reforms and tourism barriers were considered. Estimation results suggest that the transportation and communication sector could reap the benefit of liberalization effects, privatization, informational networks, technical up-grading, and the modern enterprise system in Iran.

Trade and transportation are two inseparable issues in the present circumstances, due to the fact that the efficient transportation is a must for a successful trade. The transportation service companies thus make the economic cycle of the countries move by transit and transport of loads and people. The main objective of a transportation service company is gaining more profit. One of the ways to access this objective is appropriate decision- making in connection with transport of load/person. Unfortunately the transportation companies are somehow unable and limited in allocation of available resources. What is most important for these companies is participation an involvement in activities that help them to reach their economic objectives, providing more profits for the country. In this research, the criteria for selection of best projects for transportation companies are defined, by using Delphi Method. The proposed projects of a transportation company are then studies and by Bernardo Decision making Method, and taking into account the specified criteria a mathematical model for selection of better project (or projects) have been represented. The optimum response for investment in transportation companies is then proposed.

Traffic accidents are among the important factors of fatalities and injuries that bring indispensable harms to social, cultural, and economic aspects of human societies. Also the increase in trip and traffic movements in the city provides economic improvements and social welfare but in return, the rate of accidents in the city increases proportionally. On the basis of well-accomplished studies, great part of accidents happens at intersections. The main factor of traffic accidents at intersections is convergence of traffic streams at one point. In many countries numerous studies have been accomplished to construct a statistical model for prediction of traffic accidents. In this paper, for the first time in Iran, in addition to construction of statistical model, neural network was employed to obtain the model for accidents prediction at intersections through some parameters such as traffic volume, geometric design and characteristics of traffic control devices for an intersection. Finally the result of statistical models and neural networks model are examined and compared. Results of the statistical and neural network models show that:1. The correlation coefficient is %95 for statistical models and %97 for neural network models. The interesting point is that the %95 has been obtained by omitting one of the variables. It means that considering the omitted variable from the model, the correlation coefficient will be reduced. Therefore for more accuracy of the prediction model, the accuracy of both models responses is satisfactory and the neural model responses are even more accurate.2. For construction of the statistical model, a specific function and relation that are compatible with the frequency of data should be used. In case of non- compatibility of the models, the constructed statistical model is not valid. But constructing of the neural model does not require description of a specific function, and the neural network is self-trained by contribution of some data. Therefore modeling with neural networks is more comfortable and easier.3. Utilization of statistical model is more comfortable in a way that considering various weights for each of the independent variables, the dependent variable is obtained easily. At the other hand the obtained coefficients in statistical models are more comprehended, compared to neural network models, but the neural networks are suitable tools for applications where the responses are important factors compared to the comprehension of the model. It means that for the latter, the obtained coefficients are not illustrative of the significance of variables, and therefore studies should be implemented for such applications. For application of neural network models the inputs should be applied to MATLAB Software so that the satisfactory output is obtained.