In 2002, the Department of Homeland Security (DHS) introduced a series of pictorial safety symbols designed to help prepare citizens in the wake of specific scenarios that might occur during a nuclear, chemical, or biological terrorist attack. However, in a study conducted by Christopher Mayhorn, Michael Wogalter, and Jennifer Bell of North Carolina State University, participants were unable to comprehend the meaning of many DHS safety symbols.
Based on published safety standards, the authors concluded that up to 79% of the DHS safety symbols are "unacceptable for communicating hazard-related information." The study, described in "Homeland Security Safety Symbols: Are We Ready?" (Ergonomics in Design, Volume 12, Number 4, Fall 2004), details the limitations of DHS safety symbols and advocates for the inclusion of human factors methods in designing more effective safety symbols and systems.
Human factors, often referred to as ergonomics, is the science that explores human capabilities and behavior and how these characteristics are incorporated into the design, evaluation, operation, and maintenace of products and systems that are intended for safe, effective, and satisfying use by people.
The researchers found that much of the message content communicated by the DHS symbols is questionable or counterintuitive. The intended action or warning that some symbols are supposed to convey is so complex that it can't be adequately captured in a simple picture. Other symbols attempt to convey abstract ideas, which many study participants failed to comprehend.