Publication Date: 2018
International Journal of Disaster Risk Reduction (22124209)27pp. 7-20
Since disasters have considerable effects on transportation networks, the functionality of an emergency transportation network can play an important role in mitigation phase, especially in developing countries that sometimes suffer the sad experience of almost complete destruction of several cities. Transportation related disaster response activities typically include search and rescue, emergency medical care and fire-fighting trips. In this paper, the emergency transportation network design problem is proposed to determine the optimal network to perform emergency response trips with high priority in the aftermath of earthquakes. The problem has three objective functions designated to identify the optimal routes for emergency vehicles considering the length, the travel time and the number of paths as performance metrics of network vulnerability. A combined approach for considering the three objectives including weighted sum and lexicographic methods is used. The proposed model is solved using a branch-and-cut solution method. The suggested method is tested on the well-known Sioux-Falls network as well as on the real-world network of Tehran metropolis, Iran. Computational experiments are conducted to examine the effects of varying the maximum network length, and the relative weights of other objectives. © 2017
Publication Date: 2014
Transport (16484142)29(1)pp. 28-35
The evaluation of railway line capacity is an important problem, which effects majority of problems in rail transportation planning. The railway capacity is dependent on infrastructure, traffic, and operating parameters. A key factor affecting railway line capacity is the impact of different train types. As the combination of different train types increases, more interference is generated. In this paper, for evaluation of train type interactions on railway line capacity, an integer-programming model for both line and line section is presented. The problem is formulated as a multicommodity network design model on a space-discrete time network. The railway capacity is calculated using data typically available to planners. The inputs of the model are the characteristic of each train type and railway line attributes. The model determines railway capacity based on train type mixes. In addition, this model considers impact of train types on capacity and waiting time. In order to show the features of the model, a case study is implemented in Iran Railways. The capacity tends to increase non-linearly with small incremental changes in parameters. The mixture of train types reduces the railway line capacity. The proposed model can help railway managers for long-term planning. © 2014 Copyright © 2014 Vilnius Gediminas Technical University (VGTU) Press.
Publication Date: 2014
Networks and Spatial Economics (1566113X)14(3-4)pp. 317-333
In this paper, a compressed timetable is generated to calculate capacity consumption for under construction railway routes using an optimization approach. Since the detailed timetable for under construction routes does not exist, the timetable is not required in the applied model. The model generates a compressed timetable based on UIC 406 method. The capacity consumption problem is formulated as a multicommodity network design model on a space-discrete time network. A local branching heuristic algorithm is proposed to solve the model. The main idea underlining the local branching algorithm is the utilization of a general mixed integer programming solver to explore neighborhoods and locally search around the best-known solution by employing tree search. The parameters of the algorithm are tuned by using design of experiments. The proposed method is implemented in Iran Railways and the results are reported. © 2014, Springer Science+Business Media New York.
