Abstract
Despite their inherent vulnerability to structural and functional degradation, transportation networks play a vital role in the aftermath of disasters by ensuring physical access to the affected communities and providing services according to the generated needs. In this setting of operational conditions and service needs which deviate from normal, a restructuring of network functions is deemed to be beneficial for overall network serviceability. In such context, this paper explores the planning of post-disaster operations on a network following a hazardous event on one of the network’s nodes. Lane reversal, demand regulation and path activation are applied to provide an optimally reconfigured network with reallocated demand, so that the network performance is maximized. The problem is formulated as a bi-level optimization model; the upper level determines the optimal network management strategy implementation scheme while the lower level assigns traffic on the network. Three performance indices are used for that purpose: the total network travel time (TNTT), the total network flow (TNF) and the special origin-destination pair (OD pair) accessibility. A genetic algorithm coupled with a traffic assignment process is used as a solution methodology. Application of the model on a real urban network proves the computational efficiency of the algorithm; the model systematically produces robust results of enhanced network performance, indicating its value as an operation planning tool.
Highlights
Impacts of natural and man-made disasters have increased in the recent years
Comparison of the optimized network with either the intact network or its non-optimized, post-disaster form is not possible in terms of objective function (OF) values. This is because the total network travel time (TNTT), the total network flow (TNF) and the special origin-destination pair (OD pair) accessibility terms do not participate in the final OF value with their true values, as these are obtained from the optimization process, but with their normalized values
This is due to the nature of the strategy; demand regulation aims at the maximization of the TNF under the condition that the flow will not overwhelm the damaged transportation infrastructures
Summary
Impacts of natural and man-made disasters have increased in the recent years. According to the World Bank [1], natural disasters, especially climate change-related ones, exhibit an upward trend in number, magnitude and impacts. To the best of the authors’ knowledge, it is the first time that accessibility between a set of special OD pairs defined on a network is introduced as a performance measure in a post-disaster management context, and it is the first time that the TNTT and the TNF are coupled with one another and the special OD pair accessibility to form a combined index This combined index acts as a multi-aspect measure of performance, catching different parameters of network functionality, and is deemed to provide improved results in terms of transportation network redesign on the basis of the generated needs.
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