International Journal of Transportation EngineeringInternational Journal of Transportation Engineering
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Feed provided by International Journal of Transportation Engineering. Click to visit.Service Quality and its Importance for Rail Freight Customers
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Liberalisation process has just started in the Turkish rail market with the new law recently entered into force in order to comply with EU Directives. In the liberalised markets, service quality is the decisive factor that rail undertakings can use to create difference and achieve competitive advantages. The purpose of this paper is to analyse the customer perceived service quality for rail freight transport and to highlight the important service quality gaps that must be dealt in the process of market liberalisation. The analysis is based on the findings of the survey conducted by interviewing rail stakeholders to understand their perceptions on rail service quality. The results of the research revealed that the widest quality gap relates to “transit time” which is perceived as the most important dimension of the operational quality of the freight services. It was identified that forwarders’ service quality perception is lower than that of shippers.Mon, 30 Sep 2019 20:30:00 +0100Electric-vehicle car-sharing in one-way car-sharing systems considering depreciation costs of ...
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In recent years, car-sharing systems have been announced as a way to increase mobility and to decrease the number of single-occupant vehicles, congestion, and air pollution in many parts of the world. This study presents a linear programming model to optimize one-way car-sharing systems for electric cars considering the depreciation costs of chargers and vehicles as well as relocation cost of vehicles. In this way, the objective function consists of imposed costs to the system due to the depreciation cost of vehicles, depreciation cost of chargers, and relocation cost of vehicles. Also, the rate of depreciation and the cost of relocation is considered constant in this study. The model was implemented on small and big test networks with 2 and 100 nodes with variable parameters and demand patterns. The results indicated that managing the fleet of vehicles by relocating the vehicles among stations increases the inventory at each station and minimizes the cost for meeting all requests. Also, the results indicated that the number of required vehicles decrease with an increase in charge levels and final cost increase with an increase in depreciation rate.Mon, 30 Sep 2019 20:30:00 +0100Effects of Roadway and Traffic Characteristics on Accidents Frequency at City Entrance Zone
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More than 60% of accidents in Iran occur within 30 kilometers of cities entrance roads. Therefore the number of accidents per kilometer in these regions, in contrast to the other parts of roads is very considerable. The city of Tehran, as the capital of Iran, is the cross point of major arterials of passenger and freight transportation. Thus the evaluation of road safety, entering and exiting the city in the 30 kilometers buffer, can be considered to improve countrywide road safety. To investigate the effects of roadway characteristics and traffic conditions, including number of traffic violations, on accident frequency within 30 km of Tehran entrance roads, Poisson and Negative Binomial regression model were calibrated in this study. Although the goodness of fit index in Poisson model is much greater than the Negative Binomial model, the accident data dispersion in this study implies that Negative Binomial model is more appropriate to show the influences of effective variables. According to results of modeling, the variables including average daily volume, share of heavy vehicles, average daily speed violations and number of direct accesses and interchanges have effective influence on accident frequencies. Controlling access to roads and using effective actions to reduce the speed and number of speed violation can be accounted as effective policies to reduce accident frequencies within 30 km of Tehran entrance roads.Mon, 30 Sep 2019 20:30:00 +0100Transit Signal Priority: Proposing a Novel Algorithm to Decrease Delay and Environmental ...
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Intersections are considered as the most critical parts of the bus rapid transit (BRT) system. Transit signal priority is one of the efficient solutions to reduce BRT fleet delays at intersections. The aim of this study is to propose a new algorithm to decrease the BRT fleet delays at actuated intersections, while reducing the negative impacts on different approaches. The adaptive strategy is applied in this study. In the proposed algorithm, named TSPAT (Transit Signal Priority for Actuated Timing), intersection phasing is rescheduled, based on traffic conditions such as phase conditions at the time of bus arrival, the queue length of other approaches, and prioritization record in a specific time length. To assess the merits of the proposed algorithm, a before-after study is executed by applying VISSIM traffic simulation software for an actuated intersection in Isfahan city, Iran. The simulation results show that by applying the algorithm, the average delay of BRT fleets is declined by 21 % and 51% in peak and off-peak hours, respectively. Furthermore, the average speed of BRT fleets is increased by 26% and 78%, during peak and off-peak hours, respectively. The utilization of TSPAT algorithm can improve the desirability of the public transportation system along the BRT routes.Mon, 30 Sep 2019 20:30:00 +0100Logical selection of potential hub nodes in location of strategic facilities by a hybrid ...
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Hub facility location problem looks to find the most appropriate location for deploying such facilities. An important factor in such a problem is the pool of potential locations from which the optimal locations must be selected. The present research was performed to address two key objectives: identifying the factors contributing to the selection locations for hub establishment, and presenting an efficient methodology for assessing the efficiency and effectiveness of each node, followed by selecting optimal nodes for establishing potential hubs. The paper begins with a review on related literature, leading to identification and classification of the most important factors and criteria for a hub based on the required features in transportation systems. Subsequently, in order to assess all nodes, the identified factors were grouped into input and output criteria, with the extended Data Envelopment Analysis used to assess the efficiency of the nodes. Moreover, the assessment accuracy was enhanced by weighting the input and output criteria using Analytic Hierarchy Process. A significant achievement of this research was the innovative combination of Analytic Hierarchical Process and Data Envelopment Analysis by presenting a scientific model in the form of a heuristic pair-wise comparison matrix followed by adopting power eigenvector methodology. The result of this hybrid approach highlighted the nodes upon which unavailability the efficiency of other nodes was significantly affected, and new rankings of the nodes upon such unavailability. In order to validate the findings, Iranian Airport Dataset (IAD) was used.Mon, 30 Sep 2019 20:30:00 +0100Sustainable vehicle-routing problem with time windows by heterogeneous fleet of vehicles and ...
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The purpose of this study is solving a sustainable vehicle routing problem (VRP) which in this problem special features such as mixed close–open VRP, multi-depot VRP and some others which will be discussed in this section are considered for achieving closer to real life applications. Fleets of vehicle studied in this paper are heterogeneous and for each vehicle separated compartments with different capacity for each type of wastes is took into consideration. Vehicles have different limitation on traveling time, different fixed and variable cost and amount of pollutants that is emitted from them. For achieving a sustainable VRP economic, environment and society aspects should considered simultaneously which in this paper objective functions (1) to (3) respectively are about mentioned purposes; first one minimizes the cost of collecting wastes from customer’s location, second one minimizes the pollutants which are emitted from vehicles while they are collecting wastes and finally third one minimizes violation from time limitations which are exist on each customer’s location. A new mathematical mixed integer programming model is developed for solving this problem and problem is solved by CPLEX solver and augmented ɛ-constraint method. Moreover, AHP technique for making decisions is applied in order to help us to choose the best decision. Finally, sensitivity analysis is done on some important parameters.Mon, 30 Sep 2019 20:30:00 +0100Coordination of competitive advertising via investing in transportation lead time reduction
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In this study, a contract for vertical and horizontal coordination is developed in which transportation mode and carbon emissions tax play a key role in determining the values of the contract parameters. The contract is designed for simultaneous coordination of cooperative advertising and periodic review replenishment decisions of a supplier and two competitive retailers. To obtain the optimal decisions, firstly, the traditional decision-making structure is modeled. After that, the centralized structure is modeled to obtain decisions that are profitable for the whole supply chain. Finally, for convincing the competitive retailers to accept the centralized decisions, the supplier applies a lead time crashing contract in which two transportation modes, i.e. fast and slow, can be used. Considering the carbon emissions tax imposed by the government, the coordination contract is designed in such a way that the supplier considers the trade-off between reducing lead time and paying tax on carbon emissions while providing enough incentives for the competitive retailers. Results of the sensitivity analyses showed that the proposed model is profitable from economic and environmental viewpoints. From environmental viewpoint, considering the carbon tax leads to a decrease in the carbon emissions that will be released by the transportation modes. From economic viewpoint, coordinating coop (cooperative) advertising and replenishment decisions of the SC members, enhances demand and provides a higher service level, which increases the SC profit. The contract is conditionally applicable under situations where the carbon emissions tax or lead time reduction costs become high.Tue, 12 Jun 2018 19:30:00 +0100Evaluation of Methods for Computing Free-Flow Speed and Its Significance in the HCM 2010; ...
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A weaving segment occurs where two one-way traffic streams intersect by merging and ‎diverging maneuvers. These segments are considered as one of the most important elements in ‎the freeway capacity and the Level of Service analysis in the Highway Capacity Manual (HCM). ‎Free-flow speed (FFS) plays a major role in this analysis. Hence, the current study used three ‎different methods to compute FFS of a ramp-weaving segment based on field data, and then ‎employed the proposed HCM 2010 model to analyze the weaving segment based on the three ‎FFS values obtained. Ultimately, model results were compared to field data and it was found ‎that the proposed method by the HCM 2010 outperformed the other two methods in field ‎measurement of FFS. However, the considerably poor performance of the presented model by ‎the HCM 2010 in predicting the speed of non-weaving vehicles negatively affected the ultimate ‎performance of the model and caused under-predicted results. Thereby, by applying slight ‎modifications to the field measurement method of FFS for non-weaving flow, this study ‎proposed a novel method which produces significantly more favorable results compared to ‎other methods. The merit of the study becomes even more apparent by considering the context ‎in which manuals like HCM are calibrated in. Traffic models including those mentioned in ‎HCM depend on several contextual factors including vehicle technical characteristics and traffic ‎behaviour. This implies that most recent editions of manuals may not always be the most ‎accurate ones for the traffic condition throughout the highways of Iranian cities.‎Mon, 24 Sep 2018 20:30:00 +0100A fuzzy two-stage capacitated continuous p-centmedian vehicle routing problem: A self-adaptive ...
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In this paper, a two-stage continuous p-center and p-median (namely p-centmedian) problem is developed. In the first step, a location problem is studied to compare the differences between the p-center and p-median by considering facility disruption. P-center problems are common in emergency situations with aim of minimizing the maximum distance between the facilities and costumers, while p-median problem aim is to minimize the total spent distance. Moreover, an integer linear programming is developed to deal with a time-window multi-depot capacitated vehicle routing problem in order to optimize the flows between facilities. This paper compares the mentioned p-center and p-median effects along with the vehicle routing problem as a two-step integrate problem. Since both steps are NP-hard, to deal with the problem in both stages a possibilistic programming, fuzzy single-objective programming is developed and solved by an efficient algorithm, namely self-adaptive differential evolution algorithm. Considering demand as a fuzzy parameter is an important factor and makes the problem more realistic, this feature is more considerable in emergency situations such as p-center problems. To improve the performance of results, the Taguchi method is used. In order to validate the results of the mentioned algorithms of small-sized test problems are compared with GAMS, also other valid meta-heuristics are developed to be compared with the proposed algorithm in large-sized problems. The results show the capability of algorithm to generate near-optimal solutions. Also, the results demonstrate the p-median problem is more volatile against variation in the parameters while the p-center problem is more expensive.Mon, 30 Sep 2019 20:30:00 +0100Solving a new multi-objective inventory-routing problem by an imperialist competitive algorithm
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This paper considers a multi-period, multi-product inventory-routing problem in a two-level supply chain consisting of a distributor and a set of customers. This problem is modeled with the aim of minimizing bi-objectives, namely the total system cost (including startup, distribution and maintenance costs) and risk-based transportation. Products are delivered to customers by some heterogeneous vehicles with specific capacities through a direct delivery strategy. Additionally, storage capacities are limited and the shortage is assumed to be impermissible. To validate this bi-objective model, the ε-constraint method is used for solving the problem. Since problems without distribution planning are very complex to solve optimally, the problem considered in this paper also belongs to a class of NP-hard ones. Therefore, a multi-objective imperialist competitive algorithm (MOICA) as a well-known multi-objective evolutionary algorithm is used and developed to solve a number of test problems. Furthermore, the computational results are compared to show the performance of the proposed MOICA.Mon, 24 Sep 2018 20:30:00 +0100An Alternative Approach to Centroids and Connectors Pattern: Random Intra-Zonal Travel Time
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In traditional traffic assignment procedure, each traffic analysis zone is represented by one point in its geometric center which is connected to the network by several connectors. The results of studies show that different connector patterns would result up to 10% change in estimated volume and up to 20% change in total travel time. Also the different patterns of connectors can change the priority of network development projects. Because of numerous possible scenarios for connection patterns, finding the optimum pattern is very difficult. The main goal of this research is proposing a substitute approach and proper solution algorithms to increase the accuracy of traffic assignment results. In this approach, the travel time inside the zone is considered as a random variable and is used in traffic assignment process. At first, all possible candidate nodes in each zone are selected and then between each pair of these nodes in different zones, the shortest path is determined. After that, the share of each route is estimated using discrete choice models and then share of them from demand is calculated. The proposed approach is tested using a real-size network with two route choice models of Logit and Probit. The results show significant changes in total network indexes (15%) and the average error in estimating of links volumes, has been reduced by 20%. Although the calculation time may increase 10 times than before, the proposed approach leads the traffic assignment results more accurate and close to real observed links volume.Sat, 15 Jun 2019 19:30:00 +0100A Social Engineering Optimizer Algorithm for a Closed-Loop Supply Chain System with Uncertain Demand
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This paper presents a new model for a closed-loop supply chain problem under uncertainty. This model considers production, distribution, collection, recycling and disposal of items simultaneously. Because of the increased importance of the environmental factors, this model focuses on the revers flow of the supply chain and considers different types of technology for recycling centers. The model aims to minimize the establishment cost of centers, shipment cost, holding cost, collection cost and recycling cost. To face with uncertain parameters, a credibility-based possibilistic programming method is applied. Then, a social engineering optimizer algorithm is proposed to solve the problem efficiency. To validate the model and proposed algorithm, the results are compared with the results of GAMS. In addition, they prove the superiority of the proposed algorithm over a genetic algorithm to deal with problems and find better results in less running time. Finally, the behavior of the model is assessed by changing the values of parameters and the results are reported.Sun, 30 Jun 2019 19:30:00 +0100Efficiency Analysis of Road Safety Pillars by Applying the Results of a Structural Equations ...
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Assessment of road safety performance of countries and their comparison is essential in guiding future decisions. The objective of this study is to search for effective interventions in each road safety pillar in promoting safety based on the experiences of the leading countries. In this study, we first try to use the results of a structural equations model with partial least squares approach to select the index as the representative index of each road safety pillar. Then, using the data envelopment analysis method, the ratio of the fatality rate to the sum of five calculated weights for a set of developing countries is calculated and the analysis of the efficiency and ranking of the countries takes place. Through the data envelopment analysis, the inefficiency of the 15 countries was calculated and ranked accordingly. The results of structural equation model showed that Iran has had a fair amount of activity in the field of road infrastructure safety. According to the results of this analysis, Iran is in the 15th position after South Africa, which indicates the poor road safety status and the quantitative and qualitative inadequacy of activities undertaken in some of the country's road safety pillars. In this analysis, the three countries of Romania, Poland and Turkey had the lowest inefficiency, each of which could be a benchmark for the activities of other countries. The results showed that only the country of Poland was identified as a pattern of activities in Iran.Sat, 27 Jul 2019 19:30:00 +0100A Genetic Algorithm with Multiple Populations to Reduce Fuel Consumption in Supply Chain
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Reducing fuel consumption by transportation fleet in a supply chain, reduces transportation costs and consequently, the product final cost. Moreover, it reduces environmental pollution, and in some cases, it helps governments constitute less subsidies for fuels. In this paper, a supply chain scheduling is studied, with the two objective functions of minimizing the total fuel consumption, and the total order delivery time. After presenting the mathematical model of the problem, a genetic algorithm, named Social Genetic Algorithm (SGA) is proposed to solve it. The proposed algorithm helps decision makers determine the allocation of orders to the suppliers and vehicles and production and transportation scheduling to minimize total order delivery time and fuel consumption. In order for SGA performance evaluation, its results are compared with another genetic algorithm in the literature and optimal solution. Finally, a sensitivity analysis is performed on SGA. The results of comparisons also show the high performance of SGA. Moreover, by increasing the number of suppliers and vehicles and decreasing the number of orders, the value of the objective function is reduced.Sat, 27 Jul 2019 19:30:00 +0100Solving a multi-depot location-routing problem with heterogeneous vehicles and fuzzy travel ...
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A capacitated location-routing problem (CLRP) is one of the new areas of research in distribution management. It consists of two problems; locating of facilities and routing of the vehicle with a specific capacity. The purpose of the CLRP is to open a set of stores, allocate customers to established depots, and then design vehicle tours in order to minimize the total cost. In this paper, a new mathematical programming model for multi-depot location-routing problems is considered. This model considers heterogeneous vehicles and fuzzy travel times, which are innovative and practical limitations compared to the previous studies (e.g., simultaneous pickup and delivery). This makes the model close to real-world situations. After modeling, the fuzzy model is changed to a deterministic model by credibility theory. Since this problem belongs to a class of NP-hard ones because of its computational complexity, it is impossible to find the optimal solution in reasonable time. Therefore, a particle swarm optimization algorithm is proposed and designed to solve the presented model. To show the efficiency of the proposed PSO, its results are compared with the optimal solutions obtained by an exact method embedded in the optimization software. Furthermore, the proposed PSO is able to solve medium- and large-sized problem efficiently.Sat, 27 Jul 2019 19:30:00 +0100Investigating the Effect of Using Cross-Linked Polyethylene Waste as Fine Aggregate on ...
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Cross-linked polyethylene (XLPE) is an appropriate insulating material for high-voltage cables which has been widely used as electrical cable coating. In this study, Crushed XLPE wastes with different volume percentages (25, 50, and 75%) were used in hot mix asphalt (HMA) as a substitute for fine aggregates remained on sieve no. 8 whose size varies from 1.18 to 2.36 mm. The dynamic stiffness (indirect tensile test) and fatigue test (indirect tensile fatigue test) were used to evaluate the dynamic behavior of the asphalt mixtures at temperatures of 5 and 25°C. The moisture susceptibility of the asphalt mixtures was also evaluated by Marshall stability ratio (MSR). The results showed that using crushed XLPE wastes as aggregates enhanced the fatigue life and resilient modulus of asphalt mixtures at 5°C. Also, increasing the XLPE content resulted in further enhancement in the resilient modulus and fatigue life at this temperature. However, as XLPE content increased at temperature of 25°C, the resilient modulus and fatigue life were reduced. Moreover, the MSR values showed that XLPE specimens exhibits an appropriate reaction against moisture resistance.Mon, 02 Sep 2019 19:30:00 +0100Priority order for improvement of intersections using Pedestrian Crash Prediction Model
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One of the most important needs of pedestrians is safety at crossing points, especially at intersections. Intersections are important parts of the urban road network because any disruption in them reduces the capacity of the entire network. The main objective of this research is to propose an appropriate method for prioritizing urban intersections with considering the important factors affecting pedestrian crashes to promote the safety level of pedestrians at intersections of the 11th district of Tehran. In this paper, after comparing different models, finally, the negative binomial model was developed to predict the effects of a set of factors expected to the frequency of pedestrian crashes. According to the proposed model, a larger volume of pedestrians and vehicles reduced the safety of intersections. Also imposing traffic restrictions in the central business district causes increasing motorcycle flows and has led to a more dangerous area. Also, according to the results of prioritization using this method showed that the intersection of Imam Khomeini and Valiasr with an improvement potential of 6.93 has the most potential of improvement. Based on crash reduction factor, a method for estimating the effect of a variable on crash frequencies, one-unit increase in the natural logarithm of average pedestrian and vehicle volumes, commercial land use and the number of public transport stations will increase the crash frequencies by 29.82, 83.49, 56.99 and 14.34 percent, respectively. Also, when sidewalk effective widths increased by one-unit, the probability of pedestrian crashes at intersections will be reduced by 14.87 percent.Fri, 27 Sep 2019 20:30:00 +0100