  Understanding the spatiotemporal road network accessibility during a
hurricane evacuation, the level of ease of residents in an area in reaching
evacuation destination sites through the road network, is a critical component
of emergency management. While many studies have attempted to measure road
accessibility (either in the scope of evacuation or beyond), few have
considered both dynamic evacuation demand and characteristics of a hurricane.
This study proposes a methodological framework to achieve this goal. In an
interval of every six hours, the method first estimates the evacuation demand
in terms of number of vehicles per household in each county subdivision by
considering the hurricane's wind radius and track. The closest facility
analysis is then employed to model evacuees' route choices towards the
predefined evacuation destinations. The potential crowdedness index (PCI), a
metric capturing the level of crowdedness of each road segment, is then
computed by coupling the estimated evacuation demand and route choices.
Finally, the road accessibility of each sub-county is measured by calculating
the reciprocal of the sum of PCI values of corresponding roads connecting
evacuees from the sub-county to the designated destinations. The method is
applied to the entire state of Florida during Hurricane Irma in September 2017.
Results show that I-75 and I-95 northbound have a high level of congestion, and
sub-counties along the northbound I-95 suffer from the worst road
accessibility. In addition, this research performs a sensitivity analysis for
examining the impacts of different choices of behavioral response curves on
accessibility results.
