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Rad Resilient City Initiative

Effective Post-detonation Public Warnings

Formula for Writing an Effective Message for Postdetonation Public Warning

Planning for an incident of nuclear terrorism should include the development of pre-scripted, pre-vetted, and scientifically based warning messages for fallout. Below are the essential principles of an effective public warning message, drawing on an extensive evidence base about what actually motivates people to execute protective actions.1-4 A sample public warning message—one that provides initial guidance on immediate sheltering in the aftermath of a nuclear detonation—demonstrates these principles in practice. In actuality, jurisdictions will need to develop a series of time-sensitive public warning messages about protective guidance, as represented in Sample Fallout Warning Messages for the Post–Nuclear Detonation Period. Until more comprehensive resources emerge, pre-scripted fallout protective guidance messages can adopt the form modeled below and draw content from the sample fallout warning messages, in consultation with the jurisdiction’s own radiation control and public health experts.

Components of an Effective Public Warning Message

Message source: The warning message should specify who is issuing it. Since no one source is credible for everyone, a mixed group of agencies, officials, and advisors should be identified as the source of messages. Pre-incident coordination can facilitate alignment of messaging before and after an event.

Message content: Four major elements should be addressed in the message’s content:

  1. The words should describe exactly what action people should take.

  2. The message should tell people when to start taking the action and by when they should have completed it.

  3. The message should specify who should and who should not take the recommended action. It should also provide the reasons why or why not.

  4. Finally, the message should make clear what the consequences are of the hazard and how taking the protective action will decrease losses.

Message style: The way in which the message is worded and spoken influences its ability to prompt action. There are 5 elements that contribute to a message’s effectiveness:

  1. Clarity: Simply worded messages work best. This is especially challenging for a nuclear detonation, which is technically complex and difficult to explain. Nevertheless, word choice can be guided by work that has been done previously for nuclear power plant preparedness and, more recently, on message testing for nuclear terrorism.

  2. Specificity: Be as concrete as possible in telling what you want the audience to do, using local landmarks, etc.

  3. Certainty: Messages should sound authoritative and confident.

  4. Accuracy: Misinformation and misunderstandings can create confusion and quickly erode public confidence.

  5. Consistency: Messages need to be internally consistent and stable over time. If circumstances change and advice differs, this should be noted and explained.

See an example of a post-nuclear detonation public warning message (PDF).


  1. Mileti DS, Sorensen JH. Communication of emergency public warnings: a social science perspective and state-of-the-art assessment. Oak Ridge National Laboratory. ORNL-6609. August 1990.

  2. Bean H, Mileti D. RCPGP warning system integration research project; Los Angeles / National Capitol Region / New York—Final Report. National Consortium for the Study of Terrorism and Responses to Terrorism (START). November 2010.

  3. Committee on Public Response to Alerts and Warnings on Mobile Devices: Current Knowledge and Research Gaps; National Research Council. Public Response to Alerts and Warnings on Mobile Devices: Summary of a Workshop on Current Knowledge and Research Gaps. Washington, DC: National Academies Press; 2011. Accessed August 5, 2011.

  4. National Research Council. Tsunami Warning and Preparedness: An Assessment of the U.S. Tsunami Program and the Nation’s Preparedness Efforts. Washington, DC: National Academies Press; 2010.



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