فصلنامه مهندسی حمل و نقل
سال نهم شماره 1 (پیاپی 33، پاییز 1396)

Road crashes are one of main death causes in Iran. Therefore, studying accident records and roads’ safety problems are of significant importance. Human, environment and vehicles are three principal factors that may affect each crash individually or with others. The road factor is solvable by identifying and eliminating road troubles on time. The main goal in road safety audit is to solve environment and road problems. The detected points do not contribute to accidents and casualties equally. Thus, the points; risk level should be ranked in order to efficiently provide suggestions. A step-by-step method is introduced for road sections’ safety prioritization using 6 parameters of number of accidents, road side conditions, traffic signs, road markings, pavement status, and access point density. It’s the first time that five safety audit and accident factors are used in such models. Steps include field inspection, crash statistics analysis, expert interview, entropy, and TOPSIS. The case study is chosen as Sanandaj-Kamyaran road (Primary two-lane road) in Kordestan province due to its high traffic, importance and high number of accidents. The results reveal that the segments which are rich in accidental history and, also, suffer from important safety audit factors such as high intersection density and poor pavement quality, are of the highest risk.

In this paper, we consider the problem of hazardous material distribution where the distributer chooses the routes on the network, and a regulatory agency controls the behavior of the distributer to traverse the specified routes. In these circumstances, the distributer wants to select some routes to minimize the total distributing costs. Most of the time, this occurs due to selecting risky arcs in which more individuals are exposed to risk. To prevent this and increase the capability to deal with the risk of hazardous material transportation through roads, the regulatory agency obliges carriers to traverse through the most secure arcs, though imposing more distribution costs.
In reality, two decision makers may have different perceptions or asymmetric information about the network. To apply network interdiction models for real situations, we introduce the information asymmetry for these types of vehicle routing network interdiction problems and investigate its benefits and risks. For this purpose, a bi-level programming model is proposed and two bi-level meta-heuristics are suggested to solve this Stachelberg interdictor-evader game. The computational results showed that the developed co-evolutionary meta-heuristic algorithm could be more effective and more rational than the developed Bi-GA for these problems.

To resolve the problems of the power quality in traction grid, railway static power compensator (RPC) is used in present of an YΔ11 transformer. In this paper, ability of regenerative braking energy is implemented. A full-controlled bridge is used in the traction load model for return power and thus, specific coefficients are added into load current equation. In order to increase the efficiency of system and to improve the power quality, regenerative braking accompanied by RPC compensator is used. Equations reference of control scheme is considered in the transformer secondary side. In this control scheme, reference of active and reactive and harmonic currents is separated from each other and a PI controller is used to maintain a constant DC link voltage. Finally, by applying the proposed control scheme, negative sequence and harmonic current are compensated and network power factor is improved. For validation, RPC compensation theory performance is simulated by the MATLAB/SIMULINK software.

This article reflects the findings of a study on the impacts of countdown timers on safety and performance of traffic at signal controlled intersections. Parameters such as late-stopping ratio, early start ratio, number of red light violations and number of accidents were examined to consider safety impacts of these timers. Additionally, saturation flow rate, saturation headway and start-up delay parameters examined to compare capacity and traffic performance at 6 signalized intersections located in the Yazd and Sirjan cities where the countdown timers where left on and then switched off. Data required for this purpose was provided from the video recordings of video surveillance cameras. Comparison between the timer on and off situations indicated that the number of red light violations reduced by about 1.16%, when the timer was on, the number of accidents showed no clear variation and early start ratio increased by about 1.7% when the timer was on. However, Mann-Whitney test based on a 95% Confidence interval showed that there was no significant difference between these two situations. Late-stopping ratio on average reduced by about 2.34% when the timer was on and Mann-Whitney test results showed that there was a significant difference between the two situations. . Investigation on start-up delay parameter indicated that there was a significant difference between the two situations. In this regard, start-up delay of all the intersections increased by about 22.8% when the timers were off. The t test for analyzing saturation headway and saturation flow rates indicated that there was no significant difference between the two situations.

One of the issues within the field of transportation is the selection of the transportation investment projects amongst which the selection of the projects dealing with the construction of the new streets or the expansion of the existing streets is of great interest. Although much research has been dedicated to the above-mentioned area, none has solely focused upon the expansion of the streets existing within the urban transportation network. The prime objective of the current study is to select a set of streets within the urban transportation network to enable the expansion purposes (e.g. in terms of budget constraint) as well as to optimize the travel time within the network.To fulfill the aforementioned goal, a mathematical model for the selection of projects within the urban network is proposed for the situations in which merely the expansion of the existing streets is required. Then, an innovative algorithm is introduced to determine the set of candidate streets for expansion purposes. Since the problem of project selection within the urban transportation system is an NP-hard problem from the solution perspective, with one of its most time demanding components being the solution of the traffic assignment sub-problem, and given that the expansion of the existing streets does not change the body and topology of the base network, an innovative algorithm is proposed to solve the traffic assignment problem in this situation, followed by the particle swarm optimization meta heuristic algorithm to solve the project selection model.

Disorders in rail networks expand delays and reduce the reliability and stability of the schedule. Railway disruption management includes ways to manage the operations after the occurrences of unanticipated deviations from the original schedule. In this study, the temporary blockage of tracks in the rail network is regarded as a disruption. The occurrence time of blockage and its recovery time are given. In this paper, first the basic scheduling model with the objective of minimizing the total travel time of trains will be provided. The re-scheduling model is presented which is the extension of the basic model and the original schedule provided by the basic scheduling model will be used as an input for the re-scheduling model. The new plan includes a set of new departure times, dwell times, train running times and a set of new stops for trains on the rail network for passenger's praying. A heuristic approach was proposed to design the new plan within a reasonable time. To validate the model, the train re-scheduling model is tested for multiple disruption scenarios with different disruption recovery times on the Iranian rail network. The result indicates that the developed mathematical models have advantages in producing good recovery solution with respect to the time constraint.

In recent years, the number of fatalities due to such natural disasters as floods, earthquakes, storms and so on has been increasing. Large damage/fatality dimensions due to such disasters have caused relief to the affected areas and reducing the effects of disasters to be attended to. This necessitates proper management at the time of disaster which includes proper planning, organizing, directing and controlling the required activities. One of the most vital actions of disaster response phase is to provide necessary relief commodities of shelters. In this paper, a three-level network consisting of depots of vehicles, supply centers of relief commodities and shelters has been proposed for simultaneous routing and scheduling of transportation vehicles to distribute relief commodities. In relief commodities distribution operations, the possibility of getting service from each supply center by multiple vehicles, multiple depots for relief vehicles to start and capacity constraint for vehicles and commodities supplies have been intended to. The objective of the proposed model is to reduce the total time required by the transportation vehicles to reach the supply centers and shelters considering hard time windows. Next, to show the efficiency of the proposed model, we select the fourth region of Tehran city as a case study, run the model on it and present solution results. These results show that relief commodities supplies of supply centers affect total time of servicing.