Fig 1.
(A) Evacuees are generated at the sources (yellow circles) and head to the nearest shelters at the right (the house shapes) via roads. The left side comprises flood-prone areas. The closer an area to the water, the higher the risk is. Zone H is a high-risk area, and Zone L is a low-risk area. (B-D) Different shelter capacities are set as hard infrastructure properties. The shelter capacity of B is uniform, that of C is moderately nonuniform, and that of D is strongly nonuniform. The dashed lines in B-D indicate the guideline of a uniform capacity.
Fig 2.
Schematic diagram of the various evacuation institutional arrangements.
(A) Simultaneous evacuation, (B) staged evacuation in order of high-risk, moderate-risk, and low-risk zones (HML), and (C) staged evacuation in order of low-risk, moderate-risk, and high-risk regions (LMH). The black cars are the individual agents departing at the corresponding times. A yellow line indicates the final arrival time of the last evacuee. tA, tB, and tC denote the evacuation durations in A, B, and C, respectively. The blue ranges denote the time delays between the various zones.
Fig 3.
Five cases of simplified car movement at two speeds: Zero and one.
The green, yellow, or red areas represent traffic lights. The white areas are roads, and the gray areas are intersections. When a car arrives at a shelter, the evacuation process is completed.
Fig 4.
Mean evacuation duration and mean DOU, averaged over 500 simulations, as a function of the time delay under the different shelter capacity distributions and institutional arrangements.
A time delay of zero indicates simultaneous evacuation. Each column represents a different shelter capacity: (A, D) uniform, (B, E) moderately nonuniform, and (C, F) strongly nonuniform.
Fig 5.
Distributions of the suffering levels for 1500 residents under the different zone sequences: (A) LMH strategy and (B) MLH strategy. Two cases are compared under a time delay of 1000 and a moderately nonuniform shelter capacity. The color represents the different zones divided in staged evacuation.
Fig 6.
Pareto-optimal strategies considering efficiency (evacuation duration) and fairness (DOU).
Each dot represents the mean outcomes of the evacuation duration and DOU under the different settings of hard infrastructure and institutional arrangement properties (500 simulations per dot; a total of 129 dots). The marker sizes indicate the different hard infrastructure properties (the shelter capacity distributions). The shapes indicate the different zone sequences, and the colors indicate the varying time delays. The highlighted dots with red edges are the Pareto-optimal strategies, forming a Pareto frontier (connected by red lines). The 10 Pareto-optimal strategies are as follows: 1 = LHM-200-U; 2 = MHL-600-U; 3 = HML-400-U; 4 = HLM-400-U; 5 = HML-600-U; 6 = HLM-600-U; 7 = HML-800-U; 8 = HML-1000-U; 9 = HML-1000-MN; 10 = HML-1000-SN.