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2009 Annual Forum
View Abstract
Evacuations of Linear Systems
Stella So, UC Berkeley, stellaso@berkeley.edu
Carlos F. Daganzo, UC Berkeley, daganzo@ce.berkeley.edu
Conventional evacuation models are either based on mathematical programs or traffic simulation-generated outputs. None have analytically considered for the physics of a city. In this paper, the evacuation of a special case linear system – a freeway – is physically examined. Formulas for computing evacuation times and graphical solutions for queue evolution are developed. The key driver for the evacuation of linear systems is uncovered. As it turns out, the evacuation process of a linear city can be much improved by accounting for this key driver. The improvement is calculated exactly and is shown to be increased under more realistic circumstances.
A simple control strategy is found to minimize the total evacuation time. The strategy is robust and adaptive, and requires no knowledge of demand for implementation. Finally a second evacuation objective – maximizing throughput given an evacuation time constraint – is introduced. The same strategy can be shown to further optimize for the second objective. Issues surrounding the actual deployment of the strategy are discussed.