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Iman Aghayan, Nima Noii, Mehmet Metin Kunt
2012 (Vol 24), Issue 6
This paper compares two fuzzy clustering algorithms – fuzzy subtractive clustering and fuzzy C-means clustering – to a multi-layer perceptron neural network for their ability to predict the severity of crash injuries and to estimate the response time on the traffic crash data. Four clustering algorithms – hierarchical, K-means, subtractive clustering, and fuzzy C-means clustering – were used to obtain the optimum number of clusters based on the mean silhouette coefficient and R-value before applying the fuzzy clustering algorithms. The best-fit algorithms were selected according to two criteria: precision (root mean square, R-value, mean absolute errors, and sum of square error) and response time (t). The highest R-value was obtained for the multi-layer perceptron (0.89), demonstrating that the multi-layer perceptron had a high precision in traffic crash prediction among the prediction models, and that it was stable even in the presence of outliers and overlapping data. Meanwhile, in comparison with other prediction models, fuzzy subtractive clustering provided the lowest value for response time (0.284 second), 9.28 times faster than the time of multi-layer perceptron, meaning that it could lead to developing an on-line system for processing data from detectors and/or a real-time traffic database. The model can be extended through improvements based on additional data through induction procedure.
Zoltán Bokor
2012 (Vol 24), Issue 6
The exact calculation of logistics costs has become a real challenge in logistics and supply chain management. It is essential to gain reliable and accurate costing information to attain efficient resource allocation within the logistics service provider companies. Traditional costing approaches, however, may not be sufficient to reach this aim in case of complex and heterogeneous logistics service structures. So this paper intends to explore the ways of improving the cost calculation regimes of logistics service providers and show how to adopt the multi-level full cost allocation technique in logistics practice. After determining the methodological framework, a sample cost calculation scheme is developed and tested by using estimated input data. Based on the theoretical findings and the experiences of the pilot project it can be concluded that the improved costing model contributes to making logistics costing more accurate and transparent. Moreover, the relations between costs and performances also become more visible, which enhances the effectiveness of logistics planning and controlling significantly
Anita Gudelj, Danko Kezić, Stjepan Vidačić
2012 (Vol 24), Issue 6
The paper deals with the traffic control and job optimization in the marine canal system. The moving of vessels can be described as a set of discrete events and states. Some of these states can be undesirable such as conflicts and deadlocks. It is necessary to apply adequate control policy to avoid deadlocks and blocks the vessels’ moving only in the case of dangerous situation. This paper addresses the use of Petri net as modelling and scheduling tool in this context. To find better solutions the authors propose the integration of Petri net with a genetic algorithm. Also, a matrix based formal method is proposed for analyzing discrete event dynamic system (DEDS). The algorithm is developed to deal with multi-project, multi-constrained scheduling problem with shared resources. It is verified by a computer simulation using MATLAB environment.
Afshin Shariat Mohaymany, Shideh Ehteshamrad, Mohsen Babaei
2012 (Vol 24), Issue 6
This paper is concerned with the development of a resource allocation model for road networks under supply uncertainty caused by natural disasters. An optimization model is proposed to determine which links should be invested for the system to perform better while encountering natural disasters such as earthquake. The connectivity reliability and travel time reliability of origin-destinations (ODs) are selected as performance measures to do so. The Monte-Carlo simulation method is used to estimate the reliability measures and the model is solved by the genetic algorithm. The proposed model is implemented on a test network to demonstrate the results.
Hülya Olmuş, Semra Erbaş
2012 (Vol 24), Issue 6
Log-linear modelling is advanced as a procedure to identify factors that underlie the relative frequency of occurrence of various characteristics. The purpose of this study is to present a modelling effort using log-linear models to estimate the relationships between driver’s fault and carelessness and the traffic variables such as gender, accident severity, and accident time. The study was conducted in four different districts in Ankara, the capital of Turkey. There were 1,325 people selected for the study; and they were asked whether they had been in an accident. Four hundred and forty-eight of them answered that they had been involved in an accident. As drivers, 276 out of 448 people, namely 61.6%, had traffic accidents. The data on the variables, namely gender, driver’s fault and carelessness, accident severity and accident time, were collected through a questionnaire survey. Detailed information has been created based on this information. The analysis showed that the best-fit model regarding these variables was the log-linear model. Furthermore, the odds ratio between these variables, the associations of the factors with the accident severity and the contributions of various factors, and the multiple interactions between these variables were assessed. The obtained results provide valuable information in regard to preventing undesired consequences of traffic accidents.
Dragan Petrović, Milan Bižić, Milomir Gašić, Mile Savković, Vladeta Gajić
2012 (Vol 24), Issue 6
Railway transport has a very important role in economy of every country. The efficiency of railway transport depends both on the quality of transport organization and on the technical reliability of the railway rolling stock. During operation of the railway freight wagons in the last years, a large number of breaks of suspension system elements have been noticed. This feature is especially reported at four-axle double wagon for coal transport (designated Fbd) and three-axle wagon for transport of cars (designated DDam). Frequent breaks of suspension system elements reduce the efficiency of transport and in some cases cause derailment of wagons and lead to large economic losses. In this paper, the causes of breakage of suspension on both wagons (Fbd and DDam) have been analyzed, but also the possibilities of how to resolve these problems, i.e. how to reduce them to a minimum or avoid them completely.
Drago Sever
2012 (Vol 24), Issue 6
The paper is based on the question whether the existing (legislation determined) method for determining the visibility length on passive protected level railroad crossings insures the relevant level of traffic safety. It has been recognised that using of such method does not provide stopping of road driver vehicles in front of railroad crossing in all conditions. Based on such conclusion a new approach to determining visibility length on passive protected level railroad crossing is proposed. The new approach is based on the assumption that it is necessary, primarily on level railroad crossings with local roads to recognize the worst possible and expected road and weather conditions. The testing of the proposed method in the real environment has shown that at lower speeds of road vehicles there is almost no difference, and that important benefits are recognised for the speeds of 30 and 50km/h where longer stopping distances of road vehicles have been detected (road vehicle can stop safely in front of a rail crossing) with almost the same visibility lengths. The use of the proposed method could have important impact on the increase of traffic safety on passive protected level railroad crossings.
Đurđica Stojanović
2012 (Vol 24), Issue 6
Historically, very few logistic trends have caught the attention of academics and practitioners to the same extent as outsourcing. A comprehensive literature review reveals two reasons for this continual topicality. The problem complexity and the business environment dynamics – including an interaction with other main trends in logistics and modern supply chains – both led to a permanent literature gap, indicating the need to explore some new aspects of logistics outsourcing (LO). In this paper, a new LO research perspective has been explored by identifying some weaknesses in the main LO research streams and related common viewpoints which led to six ‘logistics outsourcing research paradoxes’. Each of these paradoxes is briefly described and their links with research streams and common views on LO discussed. Finally, the nature of some known opportunities for further research is better explained and some overlooked research opportunities are highlighted.
Zijia Wang, Feng Chen, Xiaohong Li
2012 (Vol 24), Issue 6
The emergency evacuation test method of rail transit station not only affects the operation safety of the station, but it also has significant influence on the scale and cost of the station. A reasonable test method should guarantee both the safety of evacuation and that the investment is neither excessive nor too conservative. The paper compares and analyzes the differences of the existing emergency evacuation test methods of rail stations in China and other regions on the evacuation load, evacuation time calculation and the capacity of egress components, etc. Based on the field survey analysis, the desired velocity distribution of pedestrians in various station facilities and the capacity of egress components have been obtained, and then the parameters of pedestrian simulation tool were calibrated. By selecting a station for the case study, an evacuation simulation model has been established, where five evacuation scenarios have been set according to different specifications and the simulation results have been carefully analyzed. Through analyzing the simulation results, some modification proposals of the current emergency evacuation test method in the design manual have been considered, including taking into account the section passenger volume, walking time on escalators and stairs of the platform, and the condition in which the escalator most critical to evacuation should be considered as out of service.
Božidar Ivanković
2012 (Vol 24), Issue 6
Robert Mittermayr, Johann Blieberger, Andreas Schöbel
2012 (Vol 24), Issue 5
Deadlock analysis for railway systems differs in several aspects from deadlock analysis in computer science. While the problem of deadlock analysis for standard computer systems is well-understood, multi-threaded embedded computer systems pose new challenges. A novel approach in this area can easily be applied to deadlock analysis in the domain of railway systems. The approach is based on Kronecker algebra. A lazy implementation of the matrix operations even allows analysing exponentially sized systems in a very efficient manner. The running time of the algorithm does not depend on the problem size but on the size of the solution. While other approaches suffer from the fact that additional constraints make the problem and its solution harder, our approach delivers its results faster if constraints are added. In addition, our approach is complete and sound for railway systems, i.e., it generates neither false positives nor false negatives.
Kire Dimanoski, Gordan Stojić, Slavko Vesković, Ilija Tanackov
2012 (Vol 24), Issue 5
The participation of the national rail networks in the European corridors requires certain modifications and their redefinition. Because the railway stations are special parts of the railway networks, they should be modernized, especially in south-eastern Europe. The main issue in the process of construction or reconstruction of railway stations is dimensioning (projection) of infrastructure facilities. The dimensioning of the infrastructure capacity is in direct correlation with the projected technology of work and the planned volume of traffic. This paper presents the simulation model which allows sizing facilities of border rail stations on the basis of the defined work and traffic technology.
Jun-Hyuk Kim, Soonhu Soh
2012 (Vol 24), Issue 5
This paper provides a case study of hub-and-spoke school bus transportation network design. The case study here utilizes a mathematical model that is the P-median optimization model to determine optimal hub locations. The P-median problem is a combinatorial optimization problem that includes many binary variables and constraints. The selected objective of the model is to minimize the total travel time satisfying other operational constraints. To elevate usability of decision making in the future, we implement the simulation model through the template model in spreadsheet platform. The developed model is used as a future reference to find operational directions of school bus managing policy and also tested on the case of Wonkwang University.
Jun-Qiang Leng, Yu-Qin Feng, Ya-Ping Zhang, Yi He
2012 (Vol 24), Issue 5
This paper discusses the travel time reliability of road network under ice and snowfall conditions. With the introduction of correction function for the influence of ice and snowfall conditions on free travel time and capacity, the function of travel time was established. According to the limitation of the current travel time reliability, the new definition was defined on the basis of quantifying the relationship between LOS (Level of Service) and travel time reliability. The breakthrough of the traditional idea that the route travel time reliability model was set by general series system was made by considering the route as a whole unit; instead of using a paralleling system; another breakthrough was made to calculate the weighted average travel time reliability of OD (Original Destination) pair. On the basis of OD pair travel time reliability, the road network reliability model was set up. A partial road network was taken as an example to validate the effectiveness and practicality of the evaluation methodology.
Leposava Puzavac, Zdenka Popović, Luka Lazarević
2012 (Vol 24), Issue 5
The analysis of track behaviour under vertical load is traditionally based on the presumption that the stresses and deformations in track elements can be determined by the application of the Winkler’s Hypothesis. The rail is considered a beam on a continuous elastic foundation. The basis of the hypothesis is a presumption about the proportionality between the load and deflection. However, it is empirically known that the track and track foundation elements in a real environment during the railway exploitation behave neither linearly, nor completely elastically. Moreover, there is a problem with unevenness of the track stiffness along the track. This paper analyses the track stiffness from the aspect of its influence on the quality of the vertical track geometry. The paper analyses optimum stiffness. Optimum stiffness is conditioned by the single stiffness of all the elements of the superstructure and substructure as well as by their mutual compatibility.
Jelena Simićević, Nada Milosavljević, Goran Maletić
2012 (Vol 24), Issue 5
Parking charge is a powerful tool for solving parking and traffic congestion problems. In order to achieve the expected effects without any adverse impact it is necessary to understand well the users’ responses to this policy. This paper, based on a sample of interviewed parking garage users, has developed binary logit model for identification and quantification of characteristics of users and trips, on which the acceptance of parking price is dependent. In addition, multinomial logit model has been made in order to predict what the users will opt for when faced with an increase in parking price. For the first time the parameter “shorten duration” has been introduced which has shown to be the most significant in making behaviour-related decisions. The results show that the users with the purpose work are the most sensitive to an increase in parking charge, what can be deemed positive for policy makers. However, great sensitivity of the users with the purpose shopping should cause their concern. The results of the multinomial model show that they would not discontinue coming into the area after all.
Martin Jacura, Lukáš Týfa
2012 (Vol 24), Issue 5
The key issue in improving the appeal of public mass transport is the optimal arrangement of transfer nodes. The objective is to propose a comfortable, simple and safe environment for both passengers and operators, and a solution which is economical to construct and operate. Although each transfer node is unique and specific, it is beneficial to have a general idea on the layout of a project to construct or reconstruct such a transfer node. This project should, in particular, stem from the traffic intensity of single transport modes, the volume of single transfer links, and the nature and significance of traffic routes. This article presents the methodology for determining the appropriate disposition of mass public transport nodes using modified decision tables (one of the tools of systems analysis) with specific data particularly applicable in the Czech Republic.
Jasmina Pašagić Škrinjar, Kristijan Rogić, Ratko Stanković
2012 (Vol 24), Issue 5
In this paper the problems of locating urban logistic terminals are studied as hub location problems that due to a large number of potential nodes in big cities belong to hard non-polynomial problems, the so-called NP-problems. The hub location problems have found wide application in physical planning of transport and telecommunication systems, especially systems of fast delivery, networks of logistic and distribution centres and cargo traffic terminals of the big cities, etc. The paper defines single and multiple allocations and studies the numerical examples. The capacitated single allocation hub location problems have been studied, with the provision of a mathematical model of selecting the location for the hubs on the network. The paper also presents the differences in the possibilities of implementing the exact and heuristic methods to solve the actual location problems of big dimensions i.e. hub problems of the big cities.
Raffaele Mauro, Marco Cattani
2012 (Vol 24), Issue 5
The road intersection design requires a choice among different layouts, for example signalized intersections or roundabouts. Generally, layouts which provide higher level of services are the most expensive ones. For this reason, the choice has to consider both fixed and variable costs, the latter consisting in the delays suffered by the drivers crossing the junction. The paper presents a procedure to compare different layouts, taking into account the costs of construction, management/maintenance and delays. The cost of delay is estimated with different traffic conditions, by the evaluation of the layout performance, in terms of delays at the approaches. With the example traffic conditions and parameters values considered in the paper, the compact roundabout turns out to be the layout with the least overall cost. The examples of sensitivity analyses are also provided to understand the cost dependence on the parameters used.
Borna Abramović
2012 (Vol 24), Issue 5
Tino Bucak
2012 (Vol 24), Issue 5
Shuguang Li
2012 (Vol 24), Issue 5
Single vehicle type dynamic marginal cost model is extended to multiple vehicle type dynamic one based on time-dependent multiple vehicle type queue analysis at a bottleneck. A dynamic link model is presented to model interactions between cars and trucks, given the link consists of two distinct segments. The first segment is the running segment on which cars (trucks) run at their free-flow speeds and the second segment is the exit queue segment. A car or a truck is assumed to be a point without length. The class-specific pi parameter is used to transform the effect of truck into passenger car equivalents, so the exit flow of cars and trucks can be calculated according to the exit capacity of a bottleneck. The analytic expression of multiple vehicle type dynamic marginal cost function is deduced under congested and uncongested conditions. Then a heuristic algorithm is presented in solving multiple vehicle type dynamic queues, tolls under system optimum and user equilibrium conditions. The numerical example illustrates the simplicity and applicability of the proposed approach.
Surafel Luleseged Tilahun, Hong Choon Ong
2012 (Vol 24), Issue 3
Transportation plays a vital role in the development of a country and the car is the most commonly used means. However, in third world countries long waiting time for public buses is a common problem, especially when people need to switch buses. The problem becomes critical when one considers buses joining different villages and cities. Theoretically this problem can be solved by assigning more buses on the route, which is not possible due to economical problem. Another option is to schedule the buses so that customers who want to switch buses at junction cities need not have to wait long. This paper discusses how to model single frequency routes bus timetabling as a fuzzy multiobjective optimization problem and how to solve it using preference-based genetic algorithm by assigning appropriate fuzzy preference to the need of the customers. The idea will be elaborated with an example.
Sandra Kasalica, Radisav Vukadinović, Vojkan Lučanin
2012 (Vol 24), Issue 3
Problem: The number of killed and injured persons in incidents at railway level crossings is generally increasing on the Serbian Railways, particularly at passive crossings. In this paper we researched the direct behaviour of road traffic participants at a conventional railway passive crossing. Method: Direct observational study of drivers’ behaviour at a level crossing. Results: Sixty-one road vehicle drivers were observed in the moments of train approach. The probability of crossing varies depending on the train distance and the time the driver has to cross the crossing. The drivers who have limited visibility cannot estimate the speed of the approaching train well and make more risky decisions. Conclusion: This study shows that the number of “risky crossings” is worrying as the result of such crossings is a large number of accidents with fatal consequences at the passive crossings in Serbia.
Antonino D'Andrea, Orazio Pellegrino
2012 (Vol 24), Issue 3
The operating speed is certainly one of the most important variables in the management of road safety. Its determination has been refined in the last few years by means of experimental analyses that have also sanctioned its strong link with the context in which speed surveys are carried out. In fact, even though all the algorithms proposed have a very simple analytical structure, it has been noted that they can never have a general character and thus be applied without losing a certain amount of reliability.Moreover, the technological development today achieved would allow for recording in a complete way of the road environment as modern measuring instruments provide in digital format and in an economically convenient manner a great amount of data.As such, the aim of this work is to propose a methodology that allows not only the ordering and classification of numerous important data but one that is able to recognise the presence of links of dependence between unknown variables a-priori or, in any case, of difficult analytical characterisation. The technique of clustering used in order to achieve this is preliminary to the organisation of a general fuzzy model that takes into account certain variables of input linked to the geometry of the road and to the visibility and that provides as output the operating speed.Such model has been applied to a rural road located in Messina (Italy) and the results achieved, tested with experimental surveys as well as with algorithms present in literature, are very encouraging and invite deeper exploration of the study.
Davor Brčić, Marko Šoštarić, Marko Ševrović
2012 (Vol 24), Issue 3
Dimensions of parking spaces have been subject to standardization in recent decades in the world. Different state institutions and standardization committees regulated parking space sizes based on typical passenger car size and ergonomic conditions. Most of these regulations are not following the notable growth in size of passenger cars that has been the case in the past 30 years. In that period in Croatia, a significant increase was also observed in the number of passenger cars in mid-sized and large passenger car classes thus emphasising the problem of outdated and inadequate parking space dimension standard. In this paper an analytic procedure is presented that takes into account the number and types of passenger cars registered in Croatia that leads to the determination of reference passenger car size. This reference values, as well as other relevant ergonomic standards are used to calculate the recommended parking space dimensions in Croatia. The purpose of this analysis is to produce new recommendations and suggest new design standards for parking spaces in Croatia as well as to provide analytic procedures to conduct similar researches in other areas.
Jakov Karmelić, Čedomir Dundović, Ines Kolanović
2012 (Vol 24), Issue 3
Within the whole world container traffic, the largest share of containers is in the status of repositioning. Container repositioning results from the need for harmonization between the point of empty container accumulation and the point of demand, and waiting time for the availability of the first next transport of cargo. This status of containers on the container market is the consequence of imbalances in the worldwide trade distribution on most important shipping routes. The need for fast and effective reallocation of empty containers causes high costs and often represents an obstacle affecting the efficiency of port container terminals and inland carriers.In accordance with the above issue, this paper is mainly focused on the analysis of the data concerning global container capacities and the roots of container equipment imbalances, with the aim of determining the importance of empty container management and the need for empty container micro-logistic planning at the spread port area.
Dražen Cvitanić, Deana Breški, Ivan Lovrić
2012 (Vol 24), Issue 3
The paper presents a comparison of the possibility and complexity of the calibration process of two microsimulation models. The first model CORSIM is simple for use while the second named S-Paramics is more complex software. For research purposes, a model of street network with defined geometry (number, width and purpose of lanes) has been made. The volume and distribution of traffic as well as the data about traffic signals were input in the models. Numerous simulations were performed, first with the default parameters of models, and then with the calibrated parameters. Both programs have resulted in very good prediction of the intersection capacity and discharge volumes. However, for the calibration of speed more time and effort have been made in S-Paramics in which the average speed may be higher than the defined free-flow speed. This can present a problem in determining the level of service and comparing the S-Paramics results with other simulation models and analytical method results. On the other hand S-Paramics has greater capabilities than CORSIM (roundabouts modelling, dynamic traffic assignment, opportunity to interact with traffic signals...). Thus, for each specific task, one should carefully choose an appropriate program which would result in necessary and reliable output data with minimum effort and time consumed.
Vuk Bogdanović, Nenad Milutinović, Svetozar Kostić, Nenad Ruškić
2012 (Vol 24), Issue 3
Vehicle collisions are complex processes which are determined by a large number of different parameters. The development of computer programs for simulation has made the collision analysis and reconstruction procedure easier, as well as the possibility to realise the influences of different parameters on collision processes, which was not possible while using classical methods. The quality of results of vehicle collision simulation and reconstruction is expressed by an error which is determined on the basis of the difference between vehicles stopping positions, which was obtained by the simulation of established vehicles stopping positions in real collisions. Being acquainted with the influence of collision parameters on the simulation error enables the development of more reliable models for automatic optimisation of the collision process and reduction of the number of iterations in the procedure of a collision reconstruction. Within the scope of this paper, the analysis and classification of different collision parameters have been carried out. It has been done by the degree of the influence on the error in the simulation process in the software package Virtual CRASH. Varying twenty different collision parameters on the sample of seven crash tests, their influence on the distance, trajectory and angular error has been analysed, and ten parameters with the highest level of influence (centre of gravity position from front axle of vehicle 1, restitution coefficient, collision place in longitudinal direction, collision place in transverse direction, centre of gravity height-vehicle2, centre of gravity height-vehicle1, collision angle, contact plane angle, slowing down the vehicle and vehicle movement direction) have been distinguished.
Borna Abramović, Ivica Lovrić, Vlatka Stupalo
2012 (Vol 24), Issue 3
The most common problem that the terminals face is inadequate infrastructure, long waiting times, delays, malfunctions, and unexpected problems due to which terminals are often congested for a long time, high costs, lack of expansion, etc. All this leads to reduced quality of services and the price increase for the user service. These problems do not occur only at the terminal of one type, but at all terminals. At present, the delays and uneconomical operations are unacceptable. Intermodal terminals are not immune to any of the above. In order to increase the service quality and to reduce the cost of transportation and transmission, all the bottlenecks in the process are detected and analyzed in the work. The identification and removal of the bottlenecks in the processes of transport and transfer from the initial to the final terminal increases the quality of services provided to customers. The quality of services includes shorter time of transport and transfer by using shorter routes as well as the acceptable price of the service itself.
Gordana Štefančić, Dalibor Marijan, Slobodan Kljajić
2012 (Vol 24), Issue 3
As the capital of the Republic of Croatia, Zagreb is certainly the biggest motorway interchange, as well as the origin and destination of a large number of trips. Apart from obvious advantages, road traffic with its sudden development has caused certain undesired consequences as well, out of which the focus is on the traffic network congestion, including reduction of safety level, mainly because of the greater number of traffic accidents most pronounced in the summer months. The morning and afternoon hours see the highest traffic peaks at junctions, first of all at Buzin where long queues of vehicles are formed. In order to solve the problem the capacity and level of service need to be analysed and the attention should be drawn to the possible requirement of implementing measures in order to increase the capacity and the level of service in the corridor of the Zagreb Bypass.
Nikola Trubint
2012 (Vol 24), Issue 2
The use of GIS in solving a wide variety of problems in postal operations is expanding. This approach provides the development and usage of new methods in spatial data analysis, as support in achieving a better quality of the decision-making process. The use of location analysis model based on GIS software is implemented in solving the Belgrade postal retail outlet problem. One of the most important experiences of model implementation is that the local environmental conditions have a significant impact on strategic as well as operational approach. A portion of the material included in the paper has resulted from the Serbian PTT and CPC (Canada Post Corporation) joint project Location Analysis.
Dragan Martinović, Mato Tudor, Dean Bernečić
2012 (Vol 24), Issue 2
The main purpose of a vessel is to transport goods and passengers at minimum cost. Out of the analysis of relevant global databases on ship machinery failures, it is obvious that the most frequent failures occur precisely on the generator-running diesel engines. Any failure in the electrical system can leave the ship without propulsion, even if the main engine is working properly. In that case, the consequences could be devastating: higher running expenses, damage to the ship, oil spill or substantial marine pollution. These are the reasons why solutions that will prevent the ship being unable to manoeuvre during her exploitation should be implemented. Therefore, it is necessary to define a propulsion restoration model which would not depend on the primary electrical energy. The paper provides a model of the marine auxiliary system for more reliable propulsion. This includes starting, reversing and stopping of the propulsion engine. The proposed solution of reliable propulsion model based on the use of a shaft generator and an excitation engine enables the restoration of propulsion following total failure of the electrical energy primary production system, and the self-propelled ship navigation. A ship is an important factor in the Technology of Transport, and the implementation of this model increases safety, reduces downtime, and significantly decreases hazards of pollution damage.
KEYWORDS
reliable propulsion, failure, ship auxiliary system, control, propulsion restoration
Gordan Stojić, Slavko Vesković, Ilija Tanackov, Sanjin Milinković
2012 (Vol 24), Issue 2
The provision of appropriate quality rail services has an important role in terms of railway infrastructure: quality of infrastructure maintenance, regulation of railway traffic, line capacity, speed, safety, train station organization, the allowable lines load and other infrastructure parameters.
The analysis of experiences in transforming the railway systems points to the conclusion that there is no unique solution in terms of choice for institutional rail infrastructure management modes, although more than nineteen years have passed from the beginning of the implementation of the Directive 91/440/EEC. Depending on the approach to the process of restructuring the national railway company, adopted regulations and caution in its implementation, the existence or absence of a clearly defined transport strategy, the willingness to liberalize the transport market, there are several different ways for institutional management of railway infrastructure.
A hybrid model for selection of modes of institutional rail infrastructure management was developed based on the theory of artificial intelligence, theory of fuzzy sets and theory of multicriteria optimization.
KEY WORDS
management, railway infrastructure, organizational structure, hybrid model
Zuzana Schejbalová, Alžběta Kvášová, Tomáš Mičunek, Zdenč›k Marek
2012 (Vol 24), Issue 2
The Department of Forensic Experts in Transportation at the Faculty of Transportation Sciences performed a second set of dynamic passive safety tests of a passenger car (M1 category - Škoda Octavia II) in a child pedestrian collision. The initial and test conditions were similar to those of the first set of tests in September 2009 (Škoda Roomster). The deformations of the contact zones on the frontal vehicle surface were analyzed by a 3D scanning technology (3D handy scanner). Head, thorax and pelvic resultant acceleration, acceleration of knee joint in sagittal direction and contact force on the femoral structure of the dummy (P6 dummy, 1.17m; 22kg) were measured. The aim of these tests is to provide a detailed description of pedestrian kinematics and comparison of primary and secondary impact seriousness.
KEY WORDS
passenger car, child pedestrian, primary and secondary impact, dummy instrumentation, injury criteria, 3D scanning
Saša Propadalo, Damir Bekavac, Zoran Jakšić
2012 (Vol 24), Issue 2
This paper presents an application of Poisson distribution method for managing the optimal number of spare modules of the Croatian airspace surveillance system. Out of a large number of modules and electronic parts in operation, a set of 11 critical modules are identified which have experienced failures and replacements with identical modules in three years history data. Using Poisson distribution for the failure forecasting, maintenance planner can make optimal ordering of the critical spare modules for a following period by which is possible to avoid any backordering, spare module shortage and the most important operational shutdowns. The results were the creation of the Poisson model in predicting the failure rate of radar vital modules for sizing the initial stock of spare modules to be ordered along with other electronic equipment.
KEYWORDS
optimization, spare parts, Poisson distribution, forecasting, maintenance, reliability, non-repairable parts
Franc Željko Županič, Maja Meško, Iztok Podbregar
2012 (Vol 24), Issue 2
The paper investigates the ability to learn from an aircraft accident as the opportunities for learning diminish with the decline in the accident rate. A safety compromising case is studied as the processes of aircraft accident intervention and recovery can degrade the ability of an aircraft accident investigation process to enhance aviation safety by revealing accident causation. In the case study an assessment of the Slovenian aircraft accident response system was made. For the purpose of evaluating the successfulness of aircraft accident intervention and effectiveness of recovery, a model of aircraft accident response system requirements has been developed. Based on non-conformances identified by the model of requirements, remedial measures are proposed for the enhancement of the aircraft accident response system operation. Criteria for the definition of the transition from accident intervention to recovery are derived from the assessment findings in a manner not to impede the aircraft accident investigation effectiveness and efficiency.
Jesus Gonzalez-Feliu
2012 (Vol 24), Issue 2
Freight transportation constitutes one of the main activities that influence the economy and society, as it assures a vital link between suppliers and customers and represents a major source of employment. Multi-echelon distribution is one of the most common strategies adopted by the transportation companies in an aim of cost reduction. Although vehicle routing problems are very common in operational research, they are essentially related to single-echelon cases. This paper presents the main concepts of multi-echelon distribution with cross-docks and a unified notation for the N-echelon location routing problem. A literature review is also presented, in order to list the main problems and methods that can be helpful for scientists and transportation practitioners.
Vanja Jurić, Dino Županović
2012 (Vol 24), Issue 2
This article deals with the ecological impacts of chemical substances that are found in the structure of Diesel engine exhaust gases and provides an overview of legislation that limits their maximum allowable emissions. Special consideration is given to the previously mostly neglected negative impact of particulate matter compared to the impact of carbon dioxide. Negative impact of particulates is especially noted as direct negative impact on human health whereby the expenses associated with medical treatment exceed the financial savings resulting from the usage of Diesel powered vehicles. Therefore, the paper presents the knowledge acquired through previous scientific research in the economically most developed countries, as well as the tendencies for the reduction of negative impacts of Diesel exhaust gases.
Elen Twrdy, Igor Trupac, Jurij Kolenc
2012 (Vol 24), Issue 2
For the Port of Koper the Central and Eastern European market is very important. The Port of Koper is especially interesting for goods flows relating to the exchange of goods on the East – West route (and vice versa) and bound for the EU, in particular to the catchment area of the North Adriatic ports.The year 2009 was a difficult year for business, especially due to the uncertain international economic situation. In the first nine months of 2010, 16% more goods were handled in the Port of Koper than in the same period in 2009. The container transport especially exploded in tons (45% increase) as well as in container units (40% increase). Within this period they handled 355,000 TEUs (new record) in the container terminal (214,000 TEUs in the same period on the seventh pier in Trieste).The growth of container transport in the Port of Koper as well as the beginning of construction on the new container terminal have made the reconstruction and extension of the current container terminal an absolute priority. The extension is in line with the estimated growth of traffic as well as with the exploitation of present and future terminal capacities.This paper aims to present and analyse: (I) supply chains of the flow of containerised goods through the Port of Koper to/from the countries of Central and Eastern Europe; (II) the changes which enable this boom, current state and strategies to handle even more containers in the future; (iii) market potential, current and future investments in new capacities.
Xin-Min Tang, Yun-Xiang Han
2012 (Vol 24), Issue 2
To resolve the problem of future airspace management under great traffic flow and high density condition, 4D trajectory estimation has become one of the core technologies of the next new generation air traffic control automation system. According to the flight profile and the dynamics models of different aircraft types under different flight conditions, a hybrid system model that switches the aircraft from one flight stage to another with aircraft state changing continuously in one state is constructed. Additionally, air temperature and wind speed are used to modify aircraft true airspeed as well as ground speed, and the hybrid system evolution simulation is used to estimate aircraft 4D trajectory. The case study proves that 4D trajectory estimated through hybrid system model can image the flight dynamic states of aircraft and satisfy the needs of the planned flight altitude profile.
KEY WORDS
air traffic management, 4D trajectory estimation, hybrid system model, aircraft dynamic model
Miloš Poliak
2012 (Vol 24), Issue 1
The paper defines the problem of pricing in general cargo by impact of toll in the first section. Different usage of a vehicle in individual transportation causes that it is not possible to calculate the toll uniformly for every cargo by constant price for the customer in the same transportation. The next part analyses the existing processes of the toll share for general transport described in Austria, Bohemia and Germany. None of the processes can be used for another state in general. The rest is a draft of the new method of toll share for general transport determination.
Key words: transportation, pricing, cargo, toll, road
Mustafa Özuysal, Gökmen Tayfur, Serhan Tanyel
2012 (Vol 24), Issue 1
Passenger flow estimation of transit systems is essential for new decisions about additional facilities and feeder lines. For increasing the efficiency of an existing transit line, stations which are insufficient for trip production and attraction should be examined first. Such investigation supports decisions for feeder line projects which may seem necessary or futile according to the findings. In this study, passenger flow of a light rail transit (LRT) system in Izmir, Turkey is estimated by using multiple regression and feed-forward back-propagation type of artificial neural networks (ANN). The number of alighting passengers at each station is estimated as a function of boarding passengers from other stations. It is found that ANN approach produced significantly better estimations specifically for the low passenger attractive stations. In addition, ANN is found to be more capable for the determination of trip-attractive parts of LRT lines.
Keywords: light rail transit, multiple regression, artificial neural networks, public transportation
Julijana Krajnc, Klavdij Logožar, Bojana Korošec
2012 (Vol 24), Issue 1
Both the transparent reporting of logistics costs and the related accounting of their cost drivers present a significant factor for the successful management of material flows and the related logistics activities in production companies. These costs, which are mainly reported as part of overhead (indirect) costs in such companies, usually remain hidden or are not explicitly visible when the traditional method of accounting is applied. The aim of this research is to create a model of activity-based accounting of logistics costs in a production company, and to test its efficiency in the disclosure of logistics costs compared with traditional cost accounting. The application of the model in a production company shows that an activity-based approach discloses as much as 108% more logistics costs at the level of a group of products than the traditional cost-accounting approach. Further, detailed information on logistics costs obtained in this way enables their more efficient management.
Key words: logistics costs; activity-based costing; cost allocation; cost visibility; cost management
Marinko Maslarić, Aleš Groznik, Nikolina Brnjac
2012 (Vol 24), Issue 1
For the last few decades there has been growing interest in making more integrated business decisions across larger segments of the logistic and distribution networks. Modern information technology is allowing this idea to be implemented, but there is need to develop a way of effective use of information technologies that support this business direction. In this paper a methodology to assist distribution networks reengineering with the aim of integrating logistic processes within the distribution supply chain has been promoted. The emphasis of methodology is on the business processes modelling and reengineering in the distribution network. Finally, this paper presents an oil company case study to illustrate how the methodology can be applied in practice.
Keywords: distribution process, business process modelling, reengineering, information sharing, logistics
Iztok Ostan, Borut Poljšak, Eva Podovšovnik Axelsson
2012 (Vol 24), Issue 1
The aim of the paper is to present the results of a survey of railroad employees’ motivation for a healthy lifestyle. For this purpose a specific questionnaire was developed. The study was performed on 245 Slovene railroad workers (168 of them blue-collar ones). The great majority (66.9%) were found to be overweight or obese (BMI 25 or more), with no significant difference between blue- and white-collar workers. The great majority of them were in general aware of having unhealthy nutrition and an unhealthy lifestyle.
Most of the employees felt the need to improve (at least in part) their nutrition (74.7%) and lifestyle (78.0%); the majority (67.8%) also declared that they could adopt a healthier lifestyle despite the constraints of everyday life and work conditions; however, 57.6% said that they had been already putting considerable effort into a healthier nutrition and lifestyle. Thus the effort needed to overcome constraints toward a healthier lifestyle seems to be the key problem: the majority (54.3%) would rather choose walking than running or other intensive forms of exercise; they are not ready to do it for more than one hour per day (60%), and they are not ready to give up permanently food that they like and that is considered unhealthy. The differences in motivations for a healthy lifestyle between blue- and white-collar workers were not significant at the 0.05 level.
Further research in this field is needed; however, it seems that the methods of efficient marginal modifications of lifestyle are required.
KEYWORDS
human resources management, railroad, blue-collar workers, white-collar workers, healthy lifestyle, motivations
Matej Trapečar, Martin Ivan Lipičnik, Jože Balažic
2012 (Vol 24), Issue 1
The following paper aims to illustrate certain investigative activities in the forensic analysis and examination of the scene of traffic accidents. When a traffic accident occurs, the scene must be secured as soon as possible to enable professional and proper forensic investigation. Failure to secure the accident scene might result in losing or contaminating the traces, which makes it more difficult to prove or explain trace evidence in further procedure or even makes such evidence inadmissible. The topic is discussed from the viewpoint of crime scene examination, since analysing and investigating traffic accidents requires a great deal of expertise and attention of the investigators. Complex traffic accidents include feigned accidents, hit-and-run accidents as well as accidents in which the driver and passengers, dead or alive, need to be identified. In identifying the passengers, standard criminal investigation methods as well as police forensic and forensic medicine methods are followed. Such methods include confirming the identities with identity documents, other documents and vehicle ownership, fingerprints, biological traces, fibre traces, contact traces, traces of physical injuries on the driver and passengers, etc. According to the results obtained in fingerprint detection on human skin surfaces, this method can also be applied in confirming physical contact between the driver and the passengers in the accident, e.g. in the event of moving the victims and changing the scene of the accident.
Key words: traffic accidents, accident analysis, driver's identity, passengers' position, finger marks, human skin
Danijela Pjevčević, Aleksandar Radonjić, Zlatko Hrle, Vladeta Čolić
2012 (Vol 24), Issue 1
The aim of the paper is to apply Data Envelopment Analysis (DEA) method in measuring and analyzing the efficiencies of ports on the river Danube. DEA window analysis is used to determine the efficiency of ports and to observe the possibility of changes in the port efficiency over time. A study is conducted to evaluate the efficiencies of ports on the territory of Serbia in order to identify the sources of inefficiencies and formulate proposals for improving the services of those ports and their operations through a four-year window analysis with port efficiency trends and average efficiencies. The progress is made in the measurement of port efficiency in relation to port productive activities - total area of warehouses, quay length, number of cranes and port throughput, for the Serbian river ports.
Keywords: river ports, total area of warehouses, quay length, number of cranes, port throughput, port efficiency, DEA window analysis
Grgo Luburić, Gordana Miljković, Krešimir Buntak
2012 (Vol 24), Issue 1
The aim of research is to indicate the failure to use information on road depreciation in the process of making decisions about investment into road maintenance. Depreciation as accountancy category has not been sufficiently used as managerial information and its status has been marginalised. A big problem is also the non-defined status of “emergency” maintenance which some legal subjects responsible for road management book as investment maintenance which is used to compensate for the road value, and some as expenditure, in which case the mentioned investments do not even enter the base for depreciation calculation. In writing this paper the data about the book road value were taken into consideration, the amount of depreciation as well as the data about investments into the maintenance on state roads in the period from 2001 to 2008. In data analysis the methodology of descriptive statistics and regression analysis have been implemented. The results of the study of correlation between the value of depreciation and the investment into emergency maintenance have shown that the investment amount is at the level of 74% of the depreciation amount, which indicates the underestimated depreciation rate regarding the fact that roadway condition evaluations are not in harmony with such investment.
Key words: road depreciation, periodic maintenance, road value, road management
