A GIS-Based Network Analysis to Investigating the Vulnerability of Accessibility to emergency and lifesaving facilitates under the Threats of Natural Hazards

One motivation of widely studying accessibility is that the transportation network of a city influences individuals’ mobility and therefore affects their daily activities. Despite all these, it is rare to assess its vulnerability considering the increasingly and frequently emergent natural hazards. This study aims to fill out this gap by examining the vulnerability of accessibility to emergency and lifesaving facilities under the threats of natural hazards such as earthquakes and wildfires. The results will reveal whether the existing transportation network is resilient to potential impacts from natural disasters, and point out the most vulnerable areas in terms of emergency accessibility. The findings will provide a new insight into the accessibility-based planning of promoting a safe and resilient city. With the widely used cumulative-opportunity approach, we measure accessibility by counting emergency and lifesaving facilities (e.g., shelters, hospitals, etc.) that can be reached by walking, cycling, riding transit, and driving at the block group level in San Fernando Valley, CA. With the calculated accessibility, a large number of simulations will be conducted to collect a set of pseudo data for what would happen if an arbitrary road segment or bridge is damaged by a disaster. To check this impact, the above-mentioned approach will be used to recalculate accessibility by taking out a street segment or bridge located in hazardous areas from the transportation network system, one at a time, until the number of simulations is large enough for statistical analysis. With the results, GIS analysis will be used to identify those areas where accessibility is significantly reduced compared to the original status. Possible strategies will be discussed to improve the physical conditions for those vulnerable areas such as adding facilities/services or improving transportation infrastructure.

Principal Investigator: 

Chih-Hao Wang

PI Contact Information: 


California State University, Fresno


January 2021 to December 2021

Impacts/Benefits of Implementation: 

This study will demonstrate a new research approach, using accessibility analysis, to promote a safe city under the threads of natural hazards. Accessibility analysis was often used to examine whether urban opportunities are equally distributed to everyone across a city. This study is to explore the capacity of the developed accessibility technique and use it to the maximum limit in the applications of vulnerability assessments to natural hazards. This research framework can be applied for any city which would like to mitigate the vulnerability to a natural hazard through improving the resilience of its transportation network system and considering new transportation related technologies. The vulnerability assessments through accessibility analysis in this study will reveal where is vulnerable to seismic or wildfire hazards in terms of the ease to access to emergency and lifesaving facilities in a disaster. The results will point out where is needed to allocate additional emergency and lifesaving facilities or improve the resilience of the existing emergency and rescue routes. More interestingly, the discussion of new technologies might be very helpful in terms of a lower cost for the same mitigation purpose, such as the disposing of unmanned aerial vehicles for delivering necessities during a disaster.

Project Number: