فهرست مطالب

  • Volume:6 Issue:4, 2019
  • تاریخ انتشار: 1398/02/03
  • تعداد عناوین: 7
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  • Meisam Akbarzadeh, Ahmad Mohajeri Pages 305-315

    Calibration is a conventional method which is utilized to adapt traffic models based on local situations in order to achieve best results. One of the issues regarding the efficiency of this method is whether traffic models should be calibrated only in one or two major cities of a country or calibrated based upon a comprehensive selection of cities. Therefore, this study, which has used the actual speeds, attempts to evaluate the performance of the weaving model that was proposed in the fifth edition of Highway Capacity Manual (HCM 2010) and its calibrated model, which was calibrated in Tehran highways. In this regard, adequate field-data were collected on a ramp-weaving segment in Isfahan. The procedure was of 9 fifteen-minute time steps of recording at different hours of a working day. The analysis results indicated poor and app.ropriate performances by the HCM 2010 model in estimating speeds of non-weaving and weaving vehicles, respectively, for which the RMSE (Root Mean Square Error) values were obtained as 16.34 km/h and 2.11 km/h, respectively. Moreover, not only was the calibrated model unable to improve the performance of the original model, but also it affected the original model negatively and caused a larger difference in the model output compared to the actual values. Hence, calibrated models based on metropolises such as Tehran may not necessarily be app.lied to other cities and may lead to unrealistic results. This reflect the fact that traffic patterns in two cities of one country may be highly dissimilar.

    Keywords: Weaving speed, Non-weaving speed, weaving segment, Calibration, Highway capacity manual
  • Arash Saeedi, Amir Abbas Rassafi Pages 317-329

    Walking, as an important transportation mode, plays a large part in urban transportation systems. This mode is of great importance for planners and decision-makers because of its impact on environmental and health aspects of communities. However, this mode is so complex in nature that makes it difficult to study or model. On the other hand, chaos theory studies complex dynamical nonlinear systems that are sensitive to their initial conditions. A small change in initial conditions and/or parameters, may cause a big variation in the results. That is the situation that could happen in many fields of transportation. In the current study, the pedestrian behavior in crosswalks was studied in terms of chaos theory. The well-known social force model was chosen to model pedestrian movement in crosswalks, and based on the model, sensitivity analysis with respect to its parameters was carried out. Pedestrian road crossing behavior based on Helbing social force model was simulated in Matlab codes. Then pedestrian crossing behavior was investigated to detect the chaotic behavior. It was concluded that the speed of a pedestrian when the other pedestrians are closer than 100 cm and when the number of crossing pedestrians is more than 6 is chaotic. Moreover, increasing the number of pedestrians or decreasing the distance between pedestrians increase the occurrence of chaos. Chaotic behavior of speed causes turbulence in pedestrian crossing path, and that makes the path longer. Finally, some solutions for taking the system out of chaos, and consequently making its performance better, were proposed.

    Keywords: Chaos Theory, Largest Lyapunov Exponent, pedestrian, road crossing, urban road, Social Force Model
  • Seyyed, Mahdi Hosseini, Motlagh , Samira Ebrahimi, Nazanin Nami, Joshua Ignatius Pages 331-354

    In this paper, a socially responsible supply chain consisting of one supplier and one retailer is proposed. The supplier decides on replenishment cycle multiplier and the retailer invests in corporate social responsibility (CSR) and decides on the order-up-to-level under a periodic review replenishment policy. The retailer’s decisions impact on the supplier’s probability as well as the supply chain. Therefore, the supplier proposes a lead time crashing contract to entice the retailer to participate in the coordination model. In this paper, the supplier can reduce the lead time by spending more cost and select a faster transportation mode. Two transportation modes (fast and slow) are considered in the proposed contract. By selecting a fast transportation mode, the retailer’s inventory cost and shortage will be decreased. Therefore, the retailers’ profit will be increased, while the lead time reduction cost and carbon emissions tax are imposed on the supplier under the lead time crashing contract. Numerical experiments and sensitivity analyses also show that the lead time crashing contract can coordinate the proposed model and the profit of supply chain and both members will be improved. Moreover, according to this contract the extra profit that is achieved from the coordination model is shared between both members of the supply chain fairly.

    Keywords: Transportation modes, lead time crashing contract, supply chain coordination, corporate social responsibility, periodic review inventory system
  • Behzad Bamdad Mehrabani, Babak Mirbaha Pages 355-366

    Operating speed is an index that represents drivers’ speeding behaviors on different highways and shows the comfort and safety levels they experience. Many models had been proposed in previous studies to predict operating speed and most of these works had used geometric, with few of them conducted using roadside variables to predict operating speed. Also, the operating speed study in multilane rural highways had been gained less attention by researchers. In this study, two four-lane rural highways (Kole jub-Borujerd and Borujerd-Khorramabad) had been surveyed for analyzing the operating speed. More than 13,800 spot speed data was gathered in 108 tangent and 30 curve segments. Two linear regression models were developed to predict operating speed in the tangent and curve segments using geometric and roadside factors simultaneously with the acceptable R-squared statistic (0.730 and 0.854 respectively). The results showed that segment length, guardrail median, and flat roadside configuration have a positive effect while slope, accesses density, curvature, and adjacent land use length have a negative effect on operating speed. Moreover, the sensitivity analysis demonstrates that the effect of slope on operating speed in curves is twice comparing to its effect in tangents; while, operating speed in tangents is approximately 2.5 times more sensitive to access density than operating speed in curves. Thus, it can be concluded that not only geometric features affect operating speed but also roadside features affect it. The outcomes of this study can be useful in design and safety planning studies of rural multilane highways.

    Keywords: Operating speed, roadside features, geometric features, speed prediction modeling, four-lane highways
  • Saman Sorouri Ghare, Aghaj, Ramin Sadeghian , Reza Tavakkoli, Moghaddamorcid , Ahmad Makoei Pages 367-380

    In each time period, the passengers’ demand for each route is finite and airlines compete for earning more profits. The complex competition among airlines causes some problems, such as complicating flight planning and increasing empty seats for some routes. These problems increase air pollution and fuel consumption. To solve these problems, this research studies the cooperation of the airlines with game theory and sustainable development app.roaches. To investigate the issue, the three steps are suggested as introducing the components of the multi-attribute game theory to the multi-objective model, modeling multi-objective formulation with a sustainable development app.roach, and solving the model by a multi-objective method. Pay-off functions are to maximize the profit of airlines, minimize the total difference among the No.s of flier passengers and their demand on all routes and all flight times, and minimize empty seats. All the above-mentioned objectives present economic, social, and environmental aspects of sustainable development. The results of the airline cooperation model are compared with the information about non-cooperation collected from airlines in the current form. The cooperation of airlines can improve the objective functions and the sustainable development app.roach. This research can be used to help airlines in identifying the role of cooperation in air transportation.

    Keywords: Airline, multi-objective model, cooperation, game theory, sustainable development
  • Gholam Reza Shiran , John Black, Kam Tara Pages 381-394

    A Traffic Impact Assessment (TIA) provides information on the projected traffic expected from a proposed development. A TIA also evaluates the impact of proposed development on the roadways in the immediate proximity of the proposed development. The TIA should identify potential traffic operational problems or concerns and recommend appropriate actions to reduce impacts. Draft traffic impact assessment (TIA) guidelines for various land uses in general, and for high traffic generating buildings in particular, were proposed in Iran in the middle of 2016. In formulating that report the Traffic Committee of the Iranian Building Engineering Order reviewed international experience, including that of Australia. Traffic impact assessment started in Australia in the 1960s when the traffic police exercised much authority in trying to prevent land-use developments from taking place abutting main roads. Concepts derived from queuing theory where the application of the mean service time to establish maximum traffic generation rates for a proposed development was introduced. Attached to that theory was the absorption capacity of a priority traffic stream. This latter one found its way into traffic engineering practice to provide a rational basis for assessing development applications. As experience accumulated the guidelines became refined and a second edition of Austroads’ traffic impact assessment was released in 2016. This paper presents the documentation which is expected from a developer, traffic models available to the consultants working for the developer, and importance of developer contributions require by the developer for changes to the surrounding transport network. To illustrate the process, a simple case study of a school expansion is provided. The steps taken to show the impact of an increase from 185 to 600 pupils in Sydney is illustrated. The process include traffic data collection on the surrounding streets to forecasting future traffic using appropriate models and community workshops. In the light of a practical case, the process then ends with proposing options to mitigate adverse traffic impacts of the development application. The overall work illustrates the principles of TIA and to point to the onus on all developers to manage travel demands to achieve more sustainable outcomes from urban development.

    Keywords: Traffic impact assessment, development guidelines, TIA, traffic generating building
  • Hooshang Pakdel Samadi , Jabbar Ali Zakeri, Gholamreza Nabi Bidhendi Pages 395-407

    Entry of sand dunes into the railway tracks can result in sand deposition on tracks, railway obstruction, derailment, damage to track flexibility, and impairment of electrical signs and rail fleet. The approach of the present study is to keep the route open for sand pass. Therefore, it is aimed to investigate the strategies and solutions for reducing sand aggregation on railway tracks (including construction of sand passage canals through embankments and modification of the geometric form of the track sleeper humps) and to present an optimal design for the created canals in order to provide easy movement of the sands. The fluid analyses were performed in the relevant software (via numerical modeling) based on the maximum sand passage through canals, minimum subsidence of sand at entries, and minimum deposition of sand on slabs. In this regard, using the fluid mechanics principles (aerodynamics), the design requirements and limitations were taken into account; then, various distances of the canals from railway surface as well as various geometric forms of the hump, which had appropriate aerodynamic behaviors, were designed and simulated using Rhino software. Diameter of the canal was equal to 1.5 m and located at various distances (0-2 m) from the embankment surface. The designs were simulated in Fluent software. Results of the analyses on the canals indicated that the M4-P2 canal design (2m distance from the embankment and a hump with conic circular form and height of 20 cm (M-C20) was the optimal one. Besides, it was shown that the circular-form cross-sections would remove the sands much faster than other studied forms.

    Keywords: Slab track, sand dunes, sand-absorbing region, sand flow simulation, embankment