فهرست مطالب

Transportation Engineering - Volume:7 Issue: 3, Winter 2020
  • Volume:7 Issue: 3, Winter 2020
  • تاریخ انتشار: 1399/01/06
  • تعداد عناوین: 6
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  • Iman Mohammadian Nameghi, Iman Aghayan *, Reza Behzadian, MohammadAli Mosaberpanah Pages 233-247

    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.

    Keywords: Hot Mix Asphalt, Cross-linked polyethylene, Recycling, Fine aggregates, Mechanical properties
  • Mahdi Bashirinia_AmirReza Mamdoohi *_João de Abreu e Silva Pages 246-265

    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. 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.

    Keywords: Centroid, connector, Random Access Time, Probability Density Function of Intra-Zonal Travel Time, Logit, Probit Models
  • SeyyedMahdi Hosseini Motlagh *, Samira Ebrahimi, Mina Nouri, Mohammadreza Nematollahi Pages 267-296

    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.

    Keywords: Transportation lead time, Competition, Cooperative advertising, Transportation mode, Carbon emissions tax
  • Ali Karami, Mansour Hadji Hosseinlou *, MohammadHossein Abbasi, Monteiro Figuerira Pages 297-313

    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 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 increasing in natural logarithm of average pedestrian and vehicle volumes, commercial land use and number of public transport stations will increase the crash frequencies by 29.82, 83.49, 56.99 and 14.34 percents, respectively. Also, when sidewalk effective widths increased by one-unit, the probability of pedestrian crashes at intersections will reduced by 14.87 percent.

    Keywords: Prioritizing, pedestrian accidents, negative binomial model, Urban intersection, safety
  • HamidReza Behnood *, Mina Rajabpour, AmirAbbas Rassafi, Elke Hermans Pages 315-327

    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 safety pillars in road safety capacity strengthening 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.

    Keywords: Road Safety Pillars, Road Safety Performance Analysis, Data Envelopment Analysis, Structural Equations Model
  • Meisam Akbarzadeh *, Ahmad Mohajeri Pages 329-340

    The core methodology of the Highway Capacity Manual (HCM) 2010 for freeway analyses is based on Free-Flow Speed (FFS). Moreover, weaving segments are major elements of freeway facilities that form where two one-way traffic streams intersect by merging and diverging maneuvers. Hence, this study used three different methods to compute FFS of a ramp-weaving segment, and then employed the proposed HCM 2010 model to analyze the weaving. Comparison of the model results and the field data indicated that the HCM 2010 method for field measurement of FFS outperformed the other two methods. Nonetheless, the considerably poor performance of the HCM 2010 model in predicting the speed of non-weaving vehicles adversely affected the ultimate outcome of the model and caused under-predicted results. Thus, by app.lying 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. Considering these results alongside the context in which manuals like the HCM are calibrated in, elegantly demonstrates the merit of this study because the HCM traffic models depend on several contextual factors including vehicle technical characteristics and traffic behavior. This implies that most recent editions of manuals may not always be the most accurate ones for the traffic conditions throughout the highways of Iranian cities.

    Keywords: Free-flow speed, Highway Capacity Manual, weaving segment, Operating speed, Isfahan‎