What are Evacuation Zones?

According to the FEMA, “evacuation and shelter-in-place zones allow jurisdictions to focus efforts on the most vulnerable areas and people and pre-plan and model evacuation clearance times and shelter demand, while helping to reduce the need for mass evacuations. Evacuation and shelter-in-place zones should be simple, easy to understand, and recognizable for planners, communities, and the media.” (1)

The Genasys team builds initial zones using known open-source and publicly available data and an established rules-based algorithm. This includes assessing: 

  • Threat direction and historical weather patterns
  • Geography in the Wildland Urban Interface and public lands
  • Existing infrastructure in urban/suburban areas
  • Transportation and road capacity
  • Jurisdictions for fire, sheriff, city, county
  • General population, structure count/density
  • Traffic models and clearance times

Note: Every zone has a unique identifier. A zone identifier refers to a globally unique string for identifying a specific zone down to its geometric data.

The Components of a Zone Identifier

A zone identifier consists of unique information separated by dashes. An example is: US-CA-XYU-YUB-E026-C

  • US refers to a 2 character string representing the country’s ISO 3166-1 Alpha 2 code.
  • CA refers to the country’s 2-3 character string representation for State as specified by ISO 3166-2.
  • XYU refers to a 2-3 character County abbreviation as specified by the related State. Refer to County Abbreviations
  • YUB refers to the 2-3 character City or region abbreviation as specified by the related County.
  • E026 refers to the 3-4 character or number sequence assigned to the Zone as specified by its jurisdictional authority.
  • C is optional and when present refers to a single character denoting a temporary zone split. A split is the breaking of an existing polygon into 2 or more pieces where a unique letter is used to differentiate each resulting piece of the split. These are typically temporary.

The convention provides a canonical, easily reproducible, delimited data representation of a zone’s identifier. Pieces of the identifier can be readily extracted as needed to represent a particular use case. For example in the Genasys Protect community site's Zone Details page where country and state are implied, the last 3-4 sections of the identifier can be extracted and used instead of the longer representation, e.g. XYU-YUB-E026-C.