NIST Technical Note 1779

General Guidance on Emergency 

Communication Strategies for 

Buildings

Erica D. Kuligowski 

http://dx.doi.org/10.6028/NIST.TN.1779
NIST Technical Note 1779 

General Guidance on Emergency 

Communication Strategies for 

Buildings

Erica D. Kuligowski 

Fire Research Division

Engineering Laboratory

http://dx.doi.org/10.6028/NIST.TN.1779

February 2013

U.S. Department of Commerce 

Rebecca Blank, Acting Secretary

National Institute of Standards and Technology 

Patrick D. Gallagher, Under Secretary of Commerce for Standards and Technology and Director 
Certain commercial entities, equipment, or materials may be identified in this

document in order to describe an experimental procedure or concept adequately.

Such identification is not intended to imply recommendation or endorsement by the

National Institute of Standards and Technology, nor is it intended to imply that the

entities, materials, or equipment are necessarily the best available for the purpose. 

National Institute of Standards and Technology Technical Note 1779

Natl. Inst. Stand. Technol. Tech. Note 1779, 39 pages (February 2013) 

CODEN: NTNOEF
iii

Acknowledgements

The U.S. Department of Homeland Security, Science and Technology Directorate sponsored the 

production of this material under Interagency Agreement HSHQDC-07-X-00723 with the 

National Institute of Standards and Technology. The author would also like to thank the Fire 

Protection Research Foundation (FPRF) for sponsorship of the Project Technical Panel. The 

members of the Technical Panel are listed here:

• Kathleen Almand, Fire Protection Research Foundation

• Oded Aron, Port Authority NY and NJ

• June Ballew, Cooper Notification

• Don Bliss, NI2 Center for Infrastructure Expertise (NH)

• Bob Boyer, UTC Edwards

• Robert Chandler, University of Central Florida

• Joe Collins, Dallas Fort Worth airport 

• Rita Fahy, National Fire Protection Association’s Fire Analysis and Research Division

• Daniel Finnegan, Siemens Fire

• Dave Frable, U.S. General Services Administration

• Denis Gusty, U.S. Department of Homeland Security

• Edwina Juillet, NFT/LSPwD

• Matthew Kelleher, Montgomery County Fire & Rescue

• David Killian, Walt Disney Parks and Resorts

• Amanda Kimball, Fire Protection Research Foundation

• Scott Lacey, Lacey Fire Protection Engineering

• Chris Maier, National Weather Service

• Derek Mathews, Underwriters Laboratories

• Philip Mattson, U.S. Department of Homeland Security

• Dennis Mileti, University of Colorado

• Wayne Moore, Hughes Associates, Inc.

• Rodger Reiswig, SimplexGrinnell

• Lee Richardson, National Fire Protection Association’s staff liaison

• Robert Schifiliti, RP Schifiliti and Associates 

Guidance from the Technical Panel, as well as NFPA 72’s Emergency Communications Systems 

Technical Committee, was integral in the development of this document. Thank you to the 

authors of NIST Technical Note 1733 (Steven Gwynne, Kathy Butler, Bryan Hoskins, and 

Carolyn Sandler). Also, thank you to Richard Peacock, Thomas Cleary, and Anthony Hamins for 

their review of the document before publication.

Thank you to the Industry Project Sponsors: Siemens Industry, Inc., SimplexGrinnell, 

Underwriters Laboratories, Inc., and xMatters, as well as to the Contributing Industry Project 

Sponsors: Bosch, Cooper Notification, and United Technologies.
iv

Executive Summary

When a building emergency occurs, it is not always sufficient to simply initiate alarm bells. 

Individuals may not know what the alarm bell means and as a result may respond inappropriately 

to its sound. Many buildings have installed mass notification or emergency communication 

systems, based upon requirements provided in international codes and standards, that can be used 

to disseminate audible or visually-provided information in the event of an emergency. However, 

there is a lack of guidance on how to use current emergency communication systems in the most 

effective manner. For example, buildings often use these systems to disseminate pre-recorded,

general emergency voice alarm messages that leave occupants wanting and needing further 

information before effectively responding. Especially as the use of newer technologies such as 

mobile devices or social networking tools grows, guidance on message content and 

dissemination becomes even more critical to ensure effective and safe response of building 

occupants during an emergency. 

The purpose of this report is to provide general guidance to building managers and/or building 

emergency personnel responsible for emergency communication on how to create and 

disseminate messages using basic communication modes (audible vs. visual technology). The 

guidance provided here is based on the review of 162 literature sources from a variety of social 

science and engineering disciplines (Kuligowski et al. 2012) and the prioritization of the specific 

findings extracted from each literature source. This document describes the process in which 

people receive and process information in order to take action during emergencies. Then, the 

document presents guidance on how to create and disseminate emergency information in the face 

of rapid-onset disasters – providing guidance on the dissemination of alert signals, the creation of 

the warning message, the formatting of messages for both visual and audible means, and the 

dissemination of the warning message. The document ends with a discussion of research 

questions still left unanswered, and future efforts necessary to complete a comprehensive 

document on emergency message creation and dissemination for building disasters.
v

Table of Contents

1 Introduction ...........................................................................................................................................................................................1

2 Purpose of Guidance...........................................................................................................................................................................2

3 Human Response to Emergency Warning ................................................................................................................................4

4 Barriers to Effective Emergency Response ..............................................................................................................................6

4.1 Perception.....................................................................................................................................................................................6

4.2 Attention........................................................................................................................................................................................7

4.3 Comprehension ..........................................................................................................................................................................7

4.4 Belief in Information ................................................................................................................................................................7

4.5 Personalization of Information ...........................................................................................................................................8

4.6 Protective Action .......................................................................................................................................................................8

5 Guidance on Emergency Communication Strategies for Buildings ............................................................................... 9

5.1 Alerts ...............................................................................................................................................................................................9

5.2 Warnings .....................................................................................................................................................................................11

5.2.1 The Message......................................................................................................................................11

5.2.2 Visual Warnings................................................................................................................................14

5.2.3 Audible Warnings..............................................................................................................................17

5.2.4 Dissemination of the Warning Message ............................................................................................19

5.3 Summary of Guidance............................................................................................................................................................20

6 Questions Left Unanswered ..........................................................................................................................................................22

7 Future Work.........................................................................................................................................................................................23

8 References.............................................................................................................................................................................................25
1

1 Introduction

Until very recently, it was widely assumed that telling people about an emergency incident 

would lead to panic (Tierney 2003; Quarantelli and Dynes 1972). This assumption was 

commonplace, both with the lay population and with many emergency responders. The view that 

people would panic in response to an incident (and specifically to information describing the 

incident) influenced both the notification procedures employed and the language used to report 

the incident response behavior. This assumption influenced a difficult and harmful cycle 

consisting of the following steps: people report that they had panicked, emergency officials 

continue to believe that panic is a normal response, emergency information is withheld in the 

next disaster, human response is delayed and inefficient, the situation becomes more dire, and 

human response becomes more desperate. 

It is now broadly accepted that depriving evacuees of information is more likely to lead to an 

inefficient and inappropriate response; e.g., misinterpreting the incident and the threat it poses, 

delaying their response, and ignoring safe egress routes (Mileti and Sorensen 1990). During an 

incident, people will seek information regarding the nature of the incident and what they should 

do in response to it. Unfortunately, this information may not always be easy to find, reliable, 

consistent or accurate. 

At present, many buildings and building campuses in the United States are installing mass 

notification or emergency communication systems to improve communication between the 

building or emergency officials and the public. The National Fire Alarm and Signaling Code 

(NFPA 72), 2010 edition, provides requirements for the application, performance and installation 

of emergency communication (or mass notification) technology (NFPA 2010a). However, the 

2010 edition of NFPA 72 provided little guidance on how to use these systems for effective 

emergency communication1

. Additionally, many countries use British Standard BS 5839 -- Fire 

Detection and Fire Alarm Systems for Buildings – Part 8 (BS 5839-8:2008), in which chapters 

20 and 21 discuss emergency messages and dissemination techniques. 

In the United States, there is little guidance outside of the building codes regarding the content 

and dissemination strategies for emergency messages. The people providing the messages during 

an emergency may not have the necessary tools, techniques, guidance, and training to effectively 

provide information to the public when an emergency event is imminent or unfolding. This 

problem exists across all modes of notification, whether visual, audible, tactile, or social systems 

are employed. Irrespective of the mode used, it is necessary for emergency communication to be 

effective in order to facilitate the procedural measures employed and the desired response.

The purpose of this research project, which was funded by the U.S. Department of Homeland 

Security, Science and Technology Directorate, relates specifically to the effectiveness of 

emergency notification or communication. This document presents general guidance on 

emergency communication strategies to alert and warn building occupants of impending rapid-

 1 The newest edition of NFPA 72 (2013) provides guidance for message providers on message content, formatting, 

and dissemination based, in part, upon results from this project.
2

onset events in buildings and building campuses in the United States. This guidance is based on 

the review of 162 literature sources from a variety of social science and engineering disciplines 

published in Year 1 of this research project (Kuligowski et al. 2012) and the prioritization of the 

specific findings extracted from each literature source. 

2 Purpose of Guidance

This guidance document provides an understanding of human response to emergency 

communication and the ways in which to improve this response via more effective messages, 

message formatting, and message dissemination. This document begins by describing the ways 

in which people respond to emergency cues and information. Then, the needs of message 

recipients are identified. Based upon these needs, this document provides general guidance to 

building managers, emergency personnel, alarm system manufacturers, codes/standards 

committees, or others responsible for emergency communication on how to create, format, and 

disseminate messages to all building occupants, regardless of abilities or disabilities, using basic 

communication modes (audible and visual technology)2.

The focus of this guidance is rapid-onset emergencies, or those emergencies that occur with no 

or almost no (in the case of minutes) notice, rather than slow-onset events (i.e., emergencies in 

which the occurrence is known hours or even days in advance). Examples of rapid-onset events

are included in Table 1. The events shown in Table 1 were selected from NFPA 1600, the 

Standard on Disaster/Emergency Management and Business Continuity Programs (NFPA 

2010b), which lists hazards to be evaluated when planning for emergencies. 

 2 Limited guidance is provided on the use of tactile systems due to the limited amount of research available on 

human response to these systems.
3

Table 1: Potential hazards categorized here as rapid-onset incidents.

Naturally occurring hazards Human-caused events

• Geological hazards

 Earthquake

 Tsunami

 Volcano

 Landslide/mudslide

• Meteorological hazards

 Flood, flash flood

 Fire (forest, range, urban, 

wildland, wildland urban 

interface)

 Avalanche

 Windstorm, cyclone, tornado, dust 

storm or sandstorm, water spout, 

derecho

 Lightning strike

 Geomagnetic storm

• Accidental hazards

 Hazardous material spill/release

 Explosion/fire

 Transportation accident

 Building/structure collapse

 Water control structure/dam/levee 

failure

• Intentional hazards

 Terrorism (chemical, biological, 

radiological, nuclear, cyber, arson)

 Sabotage

 Civil disturbances

 Enemy attack, war

 Insurrection 

 Physical or information security 

breach

 Workplace/school/ university violence

In this guidance document, recommendations are provided based upon the summary report of the 

literature completed in the first phase of this project (Kuligowski et al. 2012). The summary 

report includes individual annotations of 162 sources from a variety of social science and 

engineering disciplines. Additionally, over 40 pages of findings and recommendations from each 

of the 162 sources are listed in the summary report. Each of these findings was reviewed and 

prioritized using a set of criteria to develop the final set of guidance that is included in this 

document (Section 5). A list of the criteria used to prioritize the summary report’s findings is 

listed here:

• Is the finding relevant to buildings and building occupants?

• Does the finding relate to emergency conditions rather than normal/non-emergency 

conditions?

• Is the finding in agreement with theory and expert opinion on human behavior in 

emergencies?

There were findings that contradicted one another. The author attempted to reconcile these 

contradictions by siding with findings that were most aligned with well-accepted social theory of 

human behavior in natural or technological disasters. Also, findings that originated from sources 

found in archival publications received higher priority, in cases of contradicting guidance. 

However, there were some contradictory findings in which consensus was not reached, and thus, 

were not included in this guidance document. Instead, they are discussed in Section 7 of this 

report, labeled as a discussion of the questions that are still left to answer.

There are also topics of interest that were included in the summary report (Kuligowski et al. 

2012), however, that were deemed outside of the scope of this guidance document. The first 

topic that was deemed outside of the scope of this document was the mechanics of visual lighting 

systems for signage. Secondly, any guidance provided on the volume necessary for audible alert 

and warning systems was also outside of the scope of this document. Both of these topics can 
4

increase the perception (i.e., hearing or seeing) of the alert or warning message, and have been 

covered in some detail in codes/standards on mass notification systems (e.g., NFPA 72 [2013]). 

This document does not provide a detailed discussion of alerting and warning technology, and 

similarly, does not advocate for the use of one type of technology over another. The summary 

report (Kuligowski et al. 2012) provides a categorization of current mass notification technology, 

the primary senses affected by each technology, and the pros and cons of these systems for 

emergency communication purposes. Therefore, it was not necessary to provide additional 

discussion of this topic. Additionally, since the focus of this document is to provide general 

guidance on the creation of the messages themselves and general dissemination techniques, the 

identification of any one type of technology was not required.

The follow-on document in this project (Year 3) will provide more detailed guidance on message 

template development, including examples of message templates, as well as ways to test these 

messages for specific buildings. In this future guidance document, templates will be provided 

based on the emergency type (rapid-onset emergencies only), and more attention will be paid to 

technology type and how that will affect the type of message created and methods for message 

dissemination. 

Finally, this document will not provide specific guidance on the development of graphics to 

accompany alerts or warning messages. There are standards available, via NFPA (2012), ANSI 

(ANSI/NEMA A535 2011), and ISO (2011; 2007; 2004), especially ANSI/NEMA Z535.3 

Criteria for Safety Symbols (ANSI 2011), that provide guidance on the development of graphics 

for static or dynamic signage. The main focus of this guidance document is the textual message 

content, and thus, interested parties developing a pictogram or symbol for emergency 

communication should seek guidance from the standards listed above. 

3 Human Response to Emergency Warning

In contrast to the panic model previously assumed, the response of an individual during an 

incident can be better characterized as a decision-making process in which people receive 

information from their environment, interpret that information, and respond based upon their 

interpretations (Lindell and Perry 2004). Understanding this process and the factors that 

influence certain interpretations can aid in the development of better guidance on emergency 

messages and dissemination systems. 

Over the last 50 years, numerous empirical studies have sought to systematically chart the social 

processes involved in human responses to emergency incidents (Tierney, Lindell and Perry 2001; 

Mileti and Sorensen 1990; Drabek 1986; Drabek 1969). Of these, the Protective Action Decision 

Model (PADM) is selected here to structure the guidance offered (Lindell and Perry 2004). The 

PADM provides a framework that describes the information flow and decision-making that 

influences protective actions taken in response to natural and technological disasters (Lindell and 

Perry 2004), and has been recently used to analyze behavioral response to the 2001 World Trade 

Center disaster (Kuligowski 2011). 
5

Specific to public warnings and emergency information, the PADM asserts that the process of 

decision-making begins when people are first presented with cues, e.g., warning messages. The 

introduction of these messages initiates a series of processes that must occur in order for the 

individual to perform protective actions, split into pre-decisional processes (PRE-DEC, which 

determine whether a decision-making process commences), and decisional processes (DEC – the 

key components of the decision-making process itself). A simplified version of this process is 

presented below

• PRE-DEC_1: the individual must perceive or receive the cue(s); e.g., a visual signal must 

be seen.

• PRE-DEC_2: the individual must pay attention to the cue(s); i.e., given that it is possible 

for the signal to be seen, the occupant actually takes note of the signal.

• PRE-DEC_3: the individual must comprehend the cue(s) and the information that is 

being conveyed; i.e., given that the signal is noted, that the information is understood.

• DEC_1: the individual must feel that the incident suggested by the cues and/or 

information is a credible threat.

• DEC_2: the individual must personalize the threat (i.e., feel that the incident is a threat to 

them) and feel that protective action is required; i.e., something needs to be done.

• DEC_3: the individual searches for what this action might be and establishes options.

• DEC_4: the options identified are assessed (given the information available) and a final 

action selected.

• DEC_5: the individual determines whether the protective action needs to be performed 

immediately.

Initially, the individual needs to receive a cue, pay attention to it, and comprehend the meaning 

associated with the cue (i.e., that it indicates an event). These represent the three pre-decisional 

stages of the PADM (PRE-DEC1-3) – the stages that determine whether external information is 

processed such that it can inform the decision-making process (Lindell and Perry 2004). Given 

that this information is processed, it then needs to be assessed to determine whether the 

information provided is credible (DEC_1). At this stage, the individual decides if there is 

actually something occurring that may require action, sometimes referred to as warning belief 

(Mileti 1974). If the individual’s answer is yes, then he or she is said to believe the threat, and 

subsequently moves on to consider the next question in the process. 

The individual next tries to determine whether the threat is relevant to him/her (DEC_2), known 

as personalizing the threat (or risk). Research has shown that a person’s perception of personal 

risk, or “the individual’s expectation of personal exposure to death, injury, or property damage” 

is highly correlated with his/her response to the disaster (Lindell and Perry 2004:51). In this 

stage, also known as personalizing risk (Mileti and Sorensen 1990), the individual determines the 

likelihood of personal consequences that could result from the threat and asks the following: “Do 

I need to take protective action?” Essentially, at this point, which is also discussed in human 

factors research as “situation awareness” (Groner 2009), the individual tries to gain insight on 

the potential outcomes of the disaster and what those potential outcomes mean to his or her 

safety. The more certain, severe, and immediate the risk is perceived to be, the more likely the 

individual is to perform protective actions (Perry, Lindell and Greene 1981). If the cues are 
6

deemed to relate to them, the individual then determines whether it is relevant and pressing. This 

then requires the individual to determine the nature of the response required at that point in time. 

At this stage, the individual engages in a decision-making process to identify 1) what can be 

done to achieve protection, and 2) the best available method for achieving protection. This

consists of a search for protective actions (DEC_3), and the outcome of this stage is a set of 

possible protective actions from which to choose. After establishing at least one protective 

action option, an individual engages in protective action assessment (DEC_4). This involves 

assessment of the potential option(s), evaluating the option(s) in comparison with taking no 

action and continuing with normal activities, and then selecting the best method of protective 

action. 

Passage through these stages is often problematic. For example, information received can be 

incomplete, ambiguous, or contradictory, causing uncertainty in what is going on and what do to 

about it. If at any stage the individual is uncertain about the answer to a question, s/he engages in 

additional information-seeking actions. The greater the ambiguity involved in the situation, the 

more likely that individuals will search for additional information that can guide their actions, 

delaying protective action/behavior. 

4 Barriers to Effective Emergency Response

In addition to the possible lack of appropriate emergency information, there are additional 

barriers that can interrupt each stage of this process, delaying protective action. These barriers 

will be described here, organized by the stage in the decision-making process in which they 

introduce difficulty.

4.1 Perception

In the first stage of the decision-making process, occupants need to perceive the warning 

information before they decide to take action. However, there are individual factors that can 

inhibit this process, including hearing impairments, visual impairments, and situational 

conditions (such as sleeping; especially for children, older adults or those who are drug/alcohol 

impaired) that can inhibit an individual from receiving emergency information (Gwynne 2007). 

The needs of these groups of individuals should be taken into account when designing an

emergency communication system, so that the alerts and messages are received by the entire 

population, not just by those who are unimpaired and alert/awake. Additionally, all individuals, 

regardless of disability, can fall subject to disaster-induced factors, such as selective perception 

and stress (Timmons 2009; 2007). Selective perception is when an individual only 

perceives/receives certain elements of the environment, which can prohibit them from hearing or 

seeing emergency information. In a similar way, stress has been found to narrow an individual’s 

field of perception so that they also may miss important emergency information.

Environmental factors can also inhibit individuals from perceiving emergency information. 

Visual and audible “pollution”, including physical obstacles (e.g., non-emergency signage) or 

competing sounds or noises, may cause individuals to miss messaging. Additionally, 

environmental cues from the emergency (i.e., smoke or flames from a fire, loud sounds, or a 
7

chemical agent that affects vision), dust, glare, veiling reflections, and ambient illumination may 

also negatively affect perception of emergency information. 

4.2 Attention

The second step in the decision-making process is that individuals must pay attention to the 

information that they receive. There are certain states in which individuals may find themselves 

at the time of an emergency that can hinder their ability to pay attention, including drug/alcohol 

impairment, cognitive impairment and sleep deprivation. Additionally, individuals may be so 

involved or committed to certain pre-emergency activities, that they may miss cues indicating an 

emergency is taking place. Similarly, if they are part of a larger group, they can be less likely to 

pay attention to their external environment.

The environment itself can introduce factors that hinder attention. The building may be equipped 

with audible and/or visual distractions, making it difficult to distinguish a new cue (to which they 

must pay attention) from all others. This can be especially difficult for individuals who have 

become habituated to their environment and the cues around them. 

Similar to perception, disaster-induced factors can inhibit attention paid to emergency 

information. Stress and anxiety brought on by the emergency can narrow an individual’s focus 

on certain details, and once the focus is narrowed, unexpected features are simply not noticed 

(known as inattentional deafness or blindness) (Timmons 2009; 2007).

4.3 Comprehension

The third step in the decision-making process is comprehension, or understanding the 

information provided by the emergency communication system. Individual factors that can 

inhibit comprehension include untrained or unprimed individuals, age (children), non-native 

speakers (especially those who do not speak the native language at all), individuals with a 

cognitive impairment, and individuals from different cultural backgrounds than the United 

States. Even more complicated is the influence of stress (induced by the emergency) on the 

general public’s ability to understand emergency information. Verbal comprehension has been 

found to drop an average of four grade levels at high levels of stimulation, stress and distraction 

(all factors that are possible during a building emergency) (Chandler 2010).

4.4 Belief in Information

In the fourth step, individuals are required to believe the information before they are able to act 

upon it. One of the main barriers to belief is normalcy bias (Drabek 1986; Okabe and Mikami 

1982). Normalcy bias is the belief or assumption that nothing is happening to place the 

individual at risk. Regardless of the intensity of cues or information received from an emergency, 

the frequent initial assumption by building occupants is that nothing is going wrong. 

Additionally, the more people who believe this assumption, and in turn, do not act or take 

protection, the less likely others around them will take protection as well.

The source of the information is important in providing credibility to the emergency information. 

However, trusted sources for the majority of a building population may not be effective for 
8

minority or sub-group populations. One example of this is the distrust by minorities of 

government agencies during community disasters. These same inhibitions of credibility may be 

found in building emergencies as well.

Finally, the prevalence of false or unwanted alarms/messages in a building may inhibit response 

in the next building emergency. The alarm/warning system may lose credibility if it has initiated 

multiple times in instances when no emergency has materialized or occurred. 

4.5 Personalization of Information

Once building occupants perceive credibility associated with an event, they must personalize the 

risk to themselves before taking action. The main barrier to this step is optimism (or optimistic) 

bias (Kunreuther 1991). In this case, individuals are inclined to believe that even though an event 

may be happening in their building, no danger or harm will happen to them. Most individuals, 

especially after initial awareness, consider this bias as reality. 

Additionally, the lack of information regarding the emergency can hinder personalization of risk. 

For instance, if individuals do not understand or know what is going on in the building, i.e., the 

extent of the emergency, they are unable to develop a sense or perception of risk. Similarly, if 

they are not told or advised of the negative ways in which the emergency could affect them, they 

are again unable to develop an understanding of the dangers the emergency poses to them.

4.6 Protective Action

Once occupants have gone through the pre-decisional and decisional processes of the emergency 

decision-making process, they consider options for action, choose one, and decide when to act. 

However, like all other stages, there are factors that inhibit this process as well.

First, individual factors can inhibit the actions that building occupants consider and then 

eventually decide to take. These individual factors can include physical impairments, economic 

restrictions (e.g., lost pay due to missing work), and lack of training or understanding of the 

procedure (Lindell and Perry 2004). 

Certain elements in the environment can also inhibit action. Occupants are likely to make actionbased decisions based upon the environment. For example, if routes are blocked due to 

environmental conditions, that may inhibit protective action decisions. Additionally, if others in 

the environment are not taking action, this may influence others to follow suit (even though they 

may wish to act). Fear of social embarrassment has been found to influence protective action in 

various types of research settings (e.g., Latane and Darley 1970).

Finally, disaster-induced factors can inhibit action. In very serious conditions, building occupants 

may be injured, which affects their ability to take protection during an emergency.

There are ways, however, to overcome these barriers to effective response in emergencies. The 

next section will provide guidance on emergency communication strategies to improve occupant 

response in building emergencies. 
9

5 Guidance on Emergency Communication Strategies for 

Buildings

The main way to overcome barriers in taking protective action is to improve emergency 

communication in building emergencies to prompt safe and effective occupant response in 

disasters. This section provides guidance for building managers, emergency personnel, alarm 

system manufacturers, codes/standards committees, or others responsible for emergency 

communication on the ways in which alerts and warning messages should be created, formatted,

and disseminated. This guidance is based on a consensus of the emergency warning literature as 

well as social theory and expert opinion on human response to emergency information in 

disasters. This section is divided in two main parts: guidance on alerts and guidance on warning 

messages. Although these two parts often get confused, it is important to distinguish between the 

purpose of an alert and a warning message. An alert is simply meant to grab peoples’ attention 

that an emergency is taking place and there is important information that will be provided to 

them. The purpose of a warning message is to give that important information to building 

occupants. Guidance on both alerts and warnings are provided here.

5.1 Alerts

Overall, the literature suggests that it is imperative to disseminate an alert to let building 

occupants know that a warning message will follow. Regardless of whether the warning message 

is provided audibly, visually, or via tactile means, an alert is necessary to gain people’s attention

and should be provided separately from the warning message.

An alert in a building can take many forms. For audible messages, a sound or series of sounds 

can be provided3. Additionally, a word or series of words can be audibly provided. In either case, 

the important aspects of alerts are that they significantly differ from ambient sounds (Edworthy 

1998). Additionally, the building should reduce background noise when initiating audible alerts, 

and especially eliminate competing voices when disseminating audible alert messages (e.g., 

Mayhorn 2005; Edworthy 1998). 

There are many examples in the literature of audible alerts. Research has identified specific 

signals that work in different situations/circumstances. For example, the traffic research literature 

has identified an attention-demanding signal that consists of modulation between 1 and 3 Hz. In 

this example, the signal should be no longer than five seconds in duration, followed by 0.5 

seconds of silence, before the warning message begins (Dudek et al. 1978). Other research 

advises the use of pulses that not only can achieve attention, but also achieve a perception of 

urgency (Haas and Edworthy 1996; Haas and Casali 1995). The purpose of this document is not 

to suggest that one audible alert type is better than another. The examples provided come from 

different fields, none of which have been tested in building-wide, rapid-onset emergencies. Some 

 3 NOTE: No guidance is provided in this document on the sound levels for audible alerts. NFPA 72 (2013) provides 

requirements on the sound levels for audible alerts, including the sound levels for waking people up and the 

appropriate location of these audible alerts systems within the building to achieve an appropriate sound level result.
10

fire researchers have also advocated for the use of a temporal three alarm signal (to serve as both 

the alert and the warning signal in case of fire emergencies) (e.g., Ball and Bruck 2004). If the 

building manager chooses an audible alert system for the building, it should be tested for its 

success in getting occupants’ attention in the event of an emergency4. Additionally, the 

building’s alert system (in addition to the warning system) should be used as part of the buildingwide training, so that the occupants are familiar with its sounds and in turn, its meaning.

Visual alerts can also be provided. The literature has reached consensus on two main ways in 

which to provide a visual alert before disseminating a warning message. First, a signal word 

(e.g., “Alert”) can be displayed to let occupants know that a visual warning message is to follow 

(Dudek et al. 1978). The same research suggests that the signal word, as part of a visual warning 

message, can be displayed in a different color (than the warning message and any other nonemergency messages posted prior) to attract attention and ensure that occupants read that signal 

word before any other information. 

Additionally, a large amount of research in both fire and other types of emergencies have found 

that flashing lights, rather than static lighting can attract people’s attention to an emergency

(Nilsson and Frantzich 2004; Jin 2002). Currently, many buildings are equipped with strobe 

lights to attract people’s attention to a fire emergency in the building. Strobe lights are especially 

useful for individuals who are hearing impaired and/or cannot hear the fire alarm or voice 

communication system. Flashing lights can also attract attention to visual signs used to display 

emergency warning messages throughout the building or building campus (i.e., outdoor signage)

(Wogalter, Conzola and Smith-Jackson 2002). However, much debate exists around the 

appropriate color of the flashing lights. Green flashing lights, possibly due to the color of 

European exit signs and their meaning of safety, have been found to be successful in leading

occupants to exits in wayfinding experiments in Sweden (Nilsson, Frantzich, and Saunders 

2009). This guidance document does not suggest one color over another for flashing lights near 

visual signage due to contradictions in the research and factors that may cloud color 

interpretation (e.g., Mayhorn 2005), including color-blindness, old age, and cultural differences

related to color meaning. The important suggestion here is the use of flashing rather than static 

lights, preferably one standard color for all buildings, to gain attention to visual warning 

messages.

Finally, there are additional methods (other than audible and visual means) to alert building 

occupants to an emergency. Depending upon the occupancy, it will be important for building 

managers and emergency personnel to aid in the disruption of routine activities, so that building 

occupants are able to pay attention to the warning to follow. Examples are provided here as ways 

to disrupt building activities: turning up the lights; cutting power to the television, internet, or 

computer screens; ending group activities (such as a movie or play/show); and terminating visual 

or audible distractions. Technology has also been invented for waking the hearing impaired

(Thomas and Bruck 2008; National Association of the Deaf, n.d.), including various types of 

pillow or bed shakers, since nighttime sleeping reduces visual capabilities. Finally, social 

networks or face-to-face alerts (by fire wardens, for example) can provide additional means to 

alert people of an emergency.

 4 Guidance on alert and message testing will be provided in the follow-on report for this project (Year 3).
11

No matter how successful an alert signal (e.g., alarm, alert sound, strobe light) is in gaining 

people’s attention, the signal should not serve as the warning message. Alert signals are meant 

only to grab occupants’ attention and notify them that a warning message is about to be 

provided. Some technologies are better at delivering alert signals and others are better at 

delivering warning messages (National Research Council 2011). For example, 90-character short 

message service (SMS) text messages have been used to alert building occupants and community 

residents of an emergency (National Research Council 2011). However, 90 characters provide 

only a limited amount of text to warn individuals of the emergency, and thus have been 

considered more like an alert, than a warning. In this case, text alerts would still need to be 

accompanied by a follow-up warning message or provide a place where building occupants 

could go for more information on the emergency at hand. One option is providing additional 

information on a website, but there is a possibility of overloading the site when building 

occupants attempt access simultaneously. Overall, it is important that each alert signal, 

regardless of dissemination mechanism, is accompanied by a clear, consistent, concise, and 

candid warning message. The guidance on warning messages is provided in the following 

section.

5.2 Warnings

Warning messages are meant to provide information to the building occupants on the state of the 

emergency and what they are supposed to do in response to this emergency. Warning messages 

should be provided after an alert signal is given and can be provided via visual or audible means.

However, before such guidance on message format for visual and audible messages can be 

provided, it is vital to provide guidance on the content of the warning message, itself. 

5.2.1 The Message

Regardless of the method used to disseminate the warning message, there are certain 

characteristics that are required of an effective warning message. Whereas demographic factors, 

such as gender or age, and environmental factors (such as physical cues or group dynamics) have 

been found to influence occupant response to an emergency, social science disaster research has 

shown that these factors become less influential when a warning message contains certain 

important characteristics (Mileti and Sorensen 1990). 

5.2.1.1 Message Content

An effective warning message is one that is specific, consistent (with cues from the event as well 

as other messages disseminated about the emergency), certain, clear, and accurate (Mileti and 

Sorensen 1990). Also, a warning message should contain five important topics to ensure that 

building occupants have sufficient information to respond with little or no additional delay and 

information seeking (Chandler 2010; National Council on Disability 2009; Centers for Disease 

Control and Prevention 2002; Mileti and Sorensen 1990). These five topics, labeled here as the 

five W’s of any effective warning message, are as follows: 
12

1. Who is providing the message? (i.e., the source of the message)

2. What should people do? (i.e., what actions occupants should take in response to the 

emergency and if necessary, how to take these actions)

3. When do people need to act? (i.e., in rapid-onset events, the “when” is likely to be 

“immediately”)

4. Where is the emergency taking place? (i.e., who needs to act and who does not)

5. Why do people need to act? (including a description of the hazard and its 

dangers/consequences).

Whereas topics two through five discuss the emergency and what people should do in response 

to it, the first topic states that the message should identify the source. In other words, who is 

providing the message to the building occupants? It is important that the source of the message 

be someone who is perceived as credible by the building population; i.e., someone to which the 

occupants can relate or someone who is highly respected (Chandler 2010; Mileti and Sorensen 

1990). Examples of possible credible sources for buildings in the United States include the local 

fire chief, the building manager (if known), the fire safety director, or other emergency personnel 

for the building (if known). Additionally, a credible source for one part of the building 

population may not be a credible source for others within the same population (Phillips and 

Morrow 2007). Building managers and emergency personnel should understand the building 

population and from this understanding, develop a database of possible, trusted sources. The 

building population could also be surveyed to identify, in their own words, possible message 

providers within the building.

5.2.1.2 Message Order

These 5 W’s are not listed in any specific order at the moment, but are listed above to simply 

show the five categories that should be included in any warning message. No research consensus 

was reached as to the appropriate order of these five W’s in an emergency message. Traffic 

research on visual signage suggests that message providers present the problem at the top (the 

“why”), the location of the problem on the second line (“the where”), and the recommended 

action (or the “what) on the third line, without mentioning the proper ordering of the message 

source or when people need to act (Ullman, Dudek and Ullman 2005). However, research in 

information recall suggests that the most important pieces of the message should be listed first 

(Covello, Minamyer and Clayton 2007; Conrad 1989), which in disaster emergencies is often the 

“what” or the actions that people should take in response to the emergency and how they should 

take these actions. With these contradictions and very little research on this issue, no specific 

guidance can be provided at this time about message ordering.

5.2.1.3 Message Structure

Research has been conducted that can provide guidance on the language structure of an 

emergency message. First, emergency messages should be written at a 6th grade reading level or 

lower (Chandler 2010). A 6th grade reading level ensures that a U.S. population can understand 

the emergency message, since the U.S. population currently reads at an average grade level of 

10, which is often decreased by four grade levels in times of stress (Chandler 2010). Second, 

emergency messages should be written without the use of jargon and false cognates (i.e., words 
13

that are similar in another language, but mean different things) (Broersma 2009; Mayhorn 2005). 

Finally, the words that are used to describe the emergency can illicit different types of response –

i.e., words matter. There are certain types of words that can convey urgency. The use of words, 

like “deadly” and “danger” have been found to prompt a perception of urgency among the public 

(e.g., Hellier et al. 1002; Edworthy, Clift-Matthews and Crowther 1998). Additionally, the 

National Weather Service is testing a new framework in which they make use of certain “urgent 

words”, such as “immediate” and “threatens”, to understand their influence on community-based 

sheltering response in tornadoes. It will be important to monitor the results of this study and 

others to determine the appropriate use of urgent words in various types of emergency 

situations5.

There may be instances in which the type of technology used to issue warnings can limit the 

content of the message. Examples of these types of technology are SMS texts via cell phones, 

Twitter feeds (140-character limit for each tweet), smaller visual signage, pagers, and tone alert 

radios (i.e., the display itself). As mentioned earlier, these types of technologies can be used as 

alerts that lead people to other types of technology in which more information (i.e., the warning 

message) can be provided. These technologies can be used to alert individuals to the emergency

and simply provide very basic information about the emergency, including methods on how and 

where to get additional information. However, in situations where there is no time to obtain

additional information and the technology provides only limited message capabilities, the 

message writer can draft the message in a bulleted form (Wogalter, Conzola and Smith-Jackson 

2002). Bulleted warnings have been found to be effective for conveying warning message 

information when space is limited. Each of the five topics in the warning (i.e., the 5 W’s) should 

be separated as its own bullet point (Wogalter 2006).

5.2.1.4 Multiple Messages

Building managers and emergency personnel should anticipate the need to write more than one 

emergency message throughout a building disaster. Subsequent warning messages can be 

disseminated to provide feedback to building occupants, for example, if they are not following 

instructions previously given or if they become confused as to the appropriate actions to take in 

the emergency. One can envisage situations in which occupants follow others’ actions, and these 

may not necessarily be the appropriate actions. Closed-circuit television (CCTV) cameras or fire 

wardens/monitors can be used to observe evacuee behavior, and if necessary, updated messages 

can help to correct inappropriate response behavior. Warning messages can also be used to 

update previous warning messages in situations where conditions have changed. For example, a 

fire can spread to other floors where evacuees were originally told to stay in place. Warning 

messages in this situation can be used to alter previous instructions to align with the current, 

most up-to-date situation. In this instance, however, it is important to tell building occupants why

the action instructions (i.e., what to do in the emergency) have changed, so that they view the 

new message as credible. 

 5 It should be noted that the use of “urgent words” in emergency messages should not be used for every emergency 

situation produced in the building. If these “urgent words” are overused in cases when an emergency does not occur 

or a less severe (than expected) emergency occurs, building occupants are likely to dismiss rather than develop a 

perception of urgency in the next disaster (when these words are used).
14

One message type that is often forgotten in an emergency is the feedback message(s) that should 

be disseminated following an emergency. For rapid-onset events, there is often little time to 

detect the emergency and provide information about its current state (which leads to instructions

on what to do). Therefore, there may be situations, for example in the case of tornadoes, where 

alert signals and warning messages are provided and then the emergency does not materialize. 

There is also the possibility that the emergency for which building occupants were warned was 

not as severe as originally predicted. Experts suspect that these situations, and others like it, 

could lead to “cry wolf” syndrome, or the possibility that building occupants would dismiss the 

threat of the next disaster and not follow the advised protective actions (e.g., Wang and Kapucu 

2008). Even though research does not reach a consensus on the validity of “cry wolf syndrome”

(Baker 1991), there are easy ways to ensure that inaction in the next disaster does not occur. One 

way to combat this syndrome is to provide feedback messages after the “non-event” to inform 

building occupants that the alert signal and warning system operated and worked as planned and 

the reasons why the event that was originally predicted did not occur (Mileti and Sorenson 

1990). This way, the alert signal and warning system will more likely maintain credibility when 

the next rapid-onset disaster occurs.

Regardless of the type of message, and especially given the lack of consensus on message 

ordering, it is important for building managers and emergency personnel to test emergency 

messages with the building population (or a representative group of building occupants) before 

they are used. There are specific methods that one can follow to engage in message testing for 

building emergencies and the next edition of this guidance document will highlight specific 

sources for procedures to follow when testing emergency messages.

5.2.2 Visual Warnings

As messages are written, following the guidance provided above, another important factor in the 

creation of messages is the method in which they are formatted and displayed. Messages that are 

displayed visually will have different capabilities and limitations than those disseminated 

audibly. Message creators should consider different factors and make different types of decisions 

based upon the dissemination method. The first consideration is the type of visual technology 

that will be used to disseminate the messages, which can include textual visual displays, SMS 

text messages, computer pop-ups, email, internet websites, news (TV broadcast) or streaming 

broadcast over the web. Depending upon the technology chosen to display visual warning 

messages, guidance is provided here on message displays to enable occupants to see or notice the 

displayed warning, understand the warning, perceive warning credibility and risk, and respond 

appropriately. 

5.2.2.1 Noticing and Reading the Warning

Most guidance pertaining to visual warnings was found on how to improve people’s perception 

and attention of a visual signage display in buildings. Much of the guidance is from the traffic 

literature as well as human factors and ergonomics, and focuses on ways in which to improve an 

individual’s awareness of a sign and ability to read the information presented on the sign.
15

Line of Sight

Since buildings are complicated structures, it is important to place an emergency sign in a 

location where people will notice it and be able to read it from their original (pre-emergency) 

location. One reference was found on the importance of sign placement and positioning, noting 

that signs will be reliably conspicuous within 15° of the direct line of sight (Creak 1997). The 

best position for signage, however, is one in which individuals can see and read it, head-on (i.e., 

0° from the direct line of sight).

Font and Size

Other important factors in the ability to read the text on a sign are the text font and size. First, the 

literature suggests a mixture of upper and lower case letters rather than the use of all capitals 

(Sanders and McCormick 1993), which makes the text easier to read. Secondly, several 

equations are provided for the relationship between letter height and viewing distance. Overall, 

the relationship between letter height and viewing distance is as follows (from the literature):

D = 100 (to 250) * h, 

where “h” is the height of the letter and “D” is the viewing distance (Rousseau, Lamson and 

Rogers 1998; Creak 1997). The recommended relationship for older adults with lower visual 

acuity is D = 100 * h, providing a more conservative result, and ensuring that a larger population 

will be able to read the emergency message provided by the sign for all types of building 

occupancies and populations. Finally, the literature provides suggestions on stroke-to-width 

ratios of the letters, specifically 1:5 (generally), with a ratio of 1:7 suggested for lighter letters on 

a darker background (Kuhn, Garvey and Pietrucha 1997). With various literature sources 

available on this topic, it is important for the building manager or emergency personnel to 

consult the ADA Standards for Accessible Design (U.S. Department of Justice 2010) for 

additional requirements on signage, including raised characters (for tactile warnings), font 

proportions, stroke thickness, character/line spacing, character height, glare, and signage 

location.

Color and Contrast

Additionally, the literature provides guidance on other ways for improving perception of visual 

warnings. Color may be an important component of visual signage and some colors have been 

more successful than others at grabbing people’s attention. For example, green or yellow text has 

been found to be brighter than red text on visual signage (Rea, Ouellette and Clark 1985). 

However, more important than color is the contrast between the text on and the background of 

the sign. Research has shown that the contrast between the text and the background should be at 

least 30 % (Dudek et al. 1978), although recommended values could be as high as at least 60 % 

(Hablamos Juntos 2007). Finally, the use of pictorials (in lieu of or in addition to text) can also 

bring attention to the sign (Young 1991).

Presentation

When presenting warnings via television or other visual means, including visual signage, one 

basic piece of guidance is provided here so that viewers see and notice emergency information. 
16

Specific care should be taken by message providers to ensure that emergency information is not 

blocked by other signs or information. An important example is the use of closed-captioning on 

television and the use of emergency crawlers on the top or bottom of a screen (that do not 

interrupt regularly schedule programming). Captions and crawlers are often located in the same 

place on the television screen making it almost impossible for the hearing impaired (i.e., those 

most likely to use closed-captioning features) to receive emergency information (National 

Organization on Disability 2009). What seems like such an obvious recommendation is not 

always heeded in reality.

5.2.2.2 Comprehending the Pictorial/Graphic, if used

The main ways to improve message comprehension involves the development of the message 

itself; i.e., crafting the message at a 6th grade reading level and neglecting the use of jargon and 

false cognates. However, specific guidance can be provided on ways to improve comprehension 

when using pictorials or graphics to present a visual warning. As an overall measure, printed text 

should accompany symbols or pictorials used in visual warnings (e.g., Jaynes and Boles 1990). 

Although some research found that accompanying text does not provide any additional help in 

comprehension (e.g., Burt, Henningsen and Consedine 1999), no research was found that the 

provision of text hinders response. Research does suggest that a minimum number of words 

should be used to accompany graphics (Caird et al. 1997; Schmidt and Kysor 1987). Also, if 

applicable, diagrams that display a series of sequential steps (that were numbered) are more 

successful in comprehension of a process than one single graphic (Burt, Henningsen and 

Consedine 1999; Caird et al. 1997).

5.2.2.3 Perception of Credibility and Risk of the Visual Warning

The literature reviewed in the previous document (Kuligowski et al. 2012) did not provide many 

recommendations on visual warnings to improve the credibility and risk assessment phases of the 

decision-making process. The literature mentions that red can be synonymous with danger and 

green with safety (Nilsson, Frantzich and Saunders 2005). However, the interpretation of hazardrelated colors and words, for that matter, is not consistent across different cultures, and possibly, 

different populations of buildings within the United States. What is likely more effective is the 

assignment of a different color to a word or phrase that is more important than the rest of the 

message. This color-contrasted word or statement will likely be read first and will be perceived 

as more urgent than the rest (in messages where color has not already been used for another 

purpose, e.g., bilingual messages) (Dudek et al. 1978). Since expert opinion suggests that the 

“what” or action portion of an emergency message is the most important, the “action” phrase 

should be contrasted with color, if any.

Additionally, a warning message can increase in perceived credibility and risk if occupants are 

shown that others are also responding (Latane and Darley 1970). This can be done, for example,

by providing streaming video of the evacuation or sheltering events. A video of responding 

building occupants can increase trust in the warning and decrease fear or concern that they are 

the only ones responding. Similarly, providing updates on the emergency situation, also in the 

form of video (i.e., showing a video of the tornado approaching), can increase perceived 

credibility and risk. 
17

5.2.2.4 Responding to the Visual Message

Methods can be taken by creators of visual warnings to decrease response time of the greater 

building population. First, suggestions are made here for visual signage. Simultaneously 

displayed text (discrete messages), rather than a sequentially displayed message, should be used, 

if possible, in rapid-onset events. Simultaneously displayed messages on visual displays, if first 

perceived and also written for comprehension, reduce the time that occupants take to respond, 

which is most important in rapid-onset emergencies (Wang and Cao 2005). Simultaneously 

displayed text, if warranted by the population, can also be used for bilingual messages, since no 

difference was found in comprehension or response when presenting the bilingual message as an 

alternating message or a simultaneous display (of both languages). However, comprehension and 

response improves with simultaneously displayed bilingual messages if care is taken to 

differentiate the text of one language from the text of the other language, which can be done by 

using two different types of fonts or colors (Jamson, Tate and Jamson 2005). In either case, the 

use of flashing words should be limited on visual message displays, since the presence of 

flashing words has been shown to increase response time (Dudek and Ullman 2001).

5.2.3 Audible Warnings

The literature also provides guidance on the most effective ways to format audible warnings. 

There are specific warning technologies that only (or primarily) affect the aural sense; including 

public address systems (voice notification systems), automated voice dialing, satellite/AM/FM 

radio broadcasts, satellite/off-air television broadcasts, and tone alert radios. Whereas visual 

technologies can limit message length, audible warnings are often limited only by the attention 

capabilities of the audience. In other words, an audible message can play for long periods of time 

with these technology types, and the message creator and source must be careful to provide all 

important information in an appropriate length of time.

Similar to the organization of Section 5.2.2, this section will also be organized based upon the 

phases of the decision-making process. First, guidance will be given for methods to increase the 

likelihood that an individual will perceive, or hear the message. Then, guidance will be provided 

that can increase comprehension of the message for audible messages. Finally, guidance will be 

provided on the ways in which to increase credibility and risk assessment of the event when the 

warning is presented audibly.

5.2.3.1 Hearing/Receiving the Audible Warning

The literature provides some guidance on ways to improve perception of audible warnings. 

Similar to guidance given for audible alerts, it is important to reduce or eliminate competing 

voices when presenting an audible warning message. Audible messages can be provided via 

computerized (or synthesized) voice, pre-recorded human voice, or a live human voice. 

Therefore, the reduction or elimination of other voices in the background helps individuals to 

hear the warning message. Additionally, research suggests that any voice announcements also be 

accompanied by simultaneous visual text (Stout, Heppner and Brick 2004). For example, in 
18

buildings, a voice announcement can be provided at the same time as an email or text message is 

received. This allows for a larger number of building occupants, including the hearing impaired 

and the visually impaired, to receive the warning message at the same time.

5.2.3.2 Comprehending the Audible Warning

Guidance is also suggested to improve occupants’ comprehension of audible messages. Even 

though focus should be placed on message wording and creation to improve comprehension 

(Section 5.2.1), there are specific recommendations on format that can be made. First, some parts 

of the English language are more difficult to identify in speech than others. Research has shown 

that letters are more difficult to identify in speech, than numbers, which are more difficult than 

colors (Cooke, Garcia Lecumberri and Barker 2008). Therefore, labeling building exits (e.g., 

stairs or elevators) with numbers or colors, rather than letters, especially if exit designations are 

included within the emergency message, may increase message comprehension. Additionally, 

message speakers (or sources) should not be heavily accented and should speak with a speaking 

rate of approximately 175 words per minute (Dudek et al. 1978). Traffic research has shown that 

speaking rates of 110 words per minute or less are considered too slow and are perceived by the 

listening audience as unimportant (Dudek et al. 1978).

5.2.3.3 Perception of Credibility and Risk of the Audible Warning

Audible messages provide additional opportunities to influence credibility and risk perception. 

To increase the credibility of the message and the emergency discussed within the message, 

audible warnings should be delivered using a live voice. The consensus among the research 

gathered is that believability is more difficult to achieve with a synthesized-voice warning

(Hellier et al. 2002). Since higher credibility is often assigned to a live voice, buildings may wish 

to use pre-recorded messages as an alert or introduction to the live warning messages that follow. 

In this case, it is important to have the live voice message provided by a credible source who 

introduces him/herself within the message and less important to assign a credible source to the 

pre-recorded alert message. However, in cases when only pre-recorded voice messages are given 

in the building, the message should be recorded by a credible message source. One note of 

caution: if the same recorded message plays too often in building events where no emergency 

occurs, the credibility attributed to this recording (and the message source) may decrease over 

time. 

Credibility is not the only benefit offered by live voice messages. Live messages can be updated 

with new information and can be used to convey an appropriate level of urgency, if necessary 

(Proulx 2001). The ways in which urgency can be achieved via a voice message is either by 

increasing the speech rate (which contradicts the earlier recommendation to speak at a normallypaced speech rate for comprehension purposes) or by projecting a higher-pitched voice. Gender 

matters less here, than the pitch of the voice; however, in most cases, women have voices that are 

higher in pitch. 

One note should be made about conveying urgency in audible messages. The literature from a 

variety of disciplines provides insight on the various methods that can be used to convey urgency 

in alerts and warnings. As mentioned earlier, for example, urgency can be conveyed in alert 
19

signals through the use of quick pulses. Additionally, warnings using a higher-pitched voice or a 

faster speech rate, or crafted using certain words, colors or graphics can also convey urgency 

levels. However, there is little mention in the disaster/fire research literature on whether it is 

appropriate to convey urgency in emergency messaging. The human factors and ergonomics 

literature suggests that warnings and alarms should convey the level of urgency of the situation 

(Edworthy 1998); however, other disciplines remain silent on the issue. Since overuse of 

urgency, especially in situations where emergencies are downgraded or do not materialize, may 

likely lead to non-response in future disasters, urgency measures should be used selectively to 

emphasize the more dangerous, immediate, life-threatening situations. 

5.2.4 Dissemination of the Warning Message

Research has shown that individuals are information seekers in times of disaster. Therefore, it is 

important to ensure that the entire population receives (and pays attention to) the alerts and 

warning messages as soon as possible. 

5.2.4.1 Multiple Channels

One way to reach the entire population of the building or building campus is to use multiple 

channels to disseminate the warning message – including visual means, audible means, and 

tactile means. Examples of tactile means for the hearing impaired includes vibrating pagers and 

text messages, and for the visually impaired, raised characters or Braille on building signage. It is 

important for message providers to understand the messaging needs of their occupants in order to 

design an emergency communication system with the appropriate technology and credible 

message sources to reach all sub-groups within the building.

5.2.4.2 Message Repetition

Another way to reach the entire building population is through message repetition. A warning 

message should be repeated at least once, with some research advocating for message repetition 

of at least two times (Dudek et al. 1978; Huchingson, Koppa and Dudek 1978). Additionally, 

messages should be stated, in full, and then repeated, in full – rather than repeating statements 

within the same message. Research has found more success in recalling the message when the 

entire message was repeated over again, multiple times (Huchingson, Koppa and Dudek 1978). 

Finally, warning messages should be repeated at intervals, rather than consecutively (Melton 

1970). The second (or third message), provided some interval of time later, may catch a different 

population who were either busy or distracted during the time period when the first warning 

message was issued.

5.2.4.3 Timing

Warning messages should also be disseminated as early as possible. This way, building 

occupants are provided with enough time to take protection before untenable conditions occur. 

Also, face-to-face communication should accompany other audible or visual technologies, due to 

its success in prompting occupant response during emergencies.
20

5.2.4.4 Communication Type

The last point related to dissemination of warnings refers to the operation of warning technology. 

Guidance suggests that messages should be disseminated using a combination of both push and 

pull technologies (Chandler 2010). Push technologies are those that do not require individuals to 

take extra effort to receive the alert or warning message (e.g., public address systems or text 

messages); whereas pull technologies require the individual to seek additional information to 

acquire the alert/message (e.g., internet websites). Push communication is most important to use 

for alert signals as well as initial warning messages, since building occupants often require 

awareness of the incident in its initial stages. Then, once initial information is made available via 

push communication, additional information can be provided by both push and pull technologies.

5.3 Summary of Guidance

Table 2 provides a summary of the guidance offered above on both alerts and warning messages. 

The guidance is organized by the type of emergency communication (alert versus warnings) and 

then by the main topics that were used for organization, above.

Table 2: Summary of guidance on alerts and warning messages

Communication 

Topic

Section of 

Report

Guidance statement

Alerts

5.1 Alerts should be significantly different from ambient sounds

Buildings should reduce background noise when initiating audible alerts

If chosen, an alert should be tested for its success in getting occupants’ 

attention in the event of an emergency and used as part of the building-wide 

training.

Flashing rather than static lights, preferably one standard color for all 

buildings, can be used to gain attention to visual warning messages

There are additional methods to alert building occupants to an emergency: 

disruption of routine activities, tactile methods, social networks, face-to-face

An alert signal should be accompanied by a clear, consistent, concise, and 

candid warning message

Warnings – The message

5.2.1.1 A warning message should contain five important topics to ensure that 

building occupants have sufficient information to respond 

1. Who is providing the message? (i.e., the source of the message)

2. What should people do? (i.e., what actions occupants should take in 

response to the emergency and if necessary, how to take these actions)

3. When do people need to act? (i.e., in rapid-onset events, the “when” is 

likely to be “immediately”)

4. Where is the emergency taking place? (i.e., who needs to act and who 

does not)

5. Why do people need to act? (including a description of the hazard and 

its dangers/consequences)

The source of the message should be someone who is perceived as credible 

by the building population

Building managers and emergency personnel should understand the building 

population and from this understanding, develop a database of possible, 

trusted sources

5.2.1.3 Emergency messages should be written at a 6th grade reading level or lower
21

Communication 

Topic

Section of 

Report

Guidance statement

Warnings – The message, continued

5.2.1.3, cont. Emergency messages should be written without the use of jargon and false 

cognates

For limited message length, message writers could draft the message in a 

bulleted form; each of the five topics in the warning should be separated as 

its own bullet point

5.2.1.4 Building managers and emergency personnel should anticipate the need to 

write more than one emergency message throughout a building disaster: 

feedback messages or updates, for example

In update messages, tell building occupants why the information has

changed, so that the new message is viewed as credible

Provide feedback messages after a “non-event” to inform building occupants 

that the alert signal and warning system operated and worked as planned and 

the reasons why the event did not occur

Building managers and emergency personnel should test emergency 

messages with the building population

Warnings – Visual

5.2.2.1 (Line 

of sight)

Place the emergency sign in a location where people will notice it and be 

able to read it from their original (pre-emergency) location

Signs will be reliably conspicuous within 15 degrees of the direct line of 

sight

(Font and size) Text is easier to read when written with a mixture of upper and lower case 

letters rather than the use of all capitals

The recommended relationship for older adults with lower visual acuity is D 

= 100 * h, providing a more conservative result, and ensuring that a larger 

population will be able to read the emergency message

A stroke-to-width ratios of the letters is suggested as 1:5 (generally), with a 

ratio of 1:7 suggested for lighter letters on a darker background

Building managers or emergency personnel should consult the ADA 

Standards for Accessible Design (U.S. Department of Justice 2010) for 

additional requirements on signage

(Color and 

contrast)

Contrast between the text and the background should be at least 30 %, 

although recommended values could be as high as at least 60 % 

The use of pictorials (in lieu of or in addition to text) can also bring attention 

to the sign

(Presentation) Message providers should ensure that emergency information is not blocked 

by other signs or information

5.2.2.2 Printed text should accompany symbols or pictorials used in visual warnings; 

a minimum number of words should be used to accompany graphics

Diagrams that display a series of sequential steps are more successful in 

comprehension of a process than one single graphic

5.2.2.3 Use a color-contrasted word or statement for text that should be read first 

and/or be perceived as more urgent than the rest; unless color is used for 

other reasons (e.g., bilingual text)

A warning message can increase in perceived credibility and risk if 

occupants are shown that others are also responding

5.2.2.4 Simultaneously displayed text (discrete messages), rather than a sequentially 

displayed message, should be used 

Simultaneously displayed text can also be used for bilingual messages, 

especially if care is taken to differentiate the text of one language from the 

text of the other language

Limit the use of flashing words on visual message displays
22

Communication 

Topic

Section of 

Report

Guidance statement

Warnings – Audible

5.2.3.1 Other, non-alert/warning voices in the background should be reduced or 

eliminated

Any voice announcements should also be accompanied by simultaneous 

visual text

5.2.3.2 Letters are more difficult to identify in speech, than numbers, which are 

more difficult than colors

Message speakers (or sources) should not be heavily accented and should 

speak with a speaking rate of approximately 175 words per minute

Audible warnings should be delivered using a live voice

Other benefits are provided by a live voice method: messages can be updated 

with new information and can be used to convey an appropriate level of 

urgency, if necessary

Urgency measures should be used selectively to emphasize the more 

dangerous, immediate, life-threatening situations (since overuse may likely 

lead to non-response in future disasters)

Warnings – Dissemination

5.2.4.1 Use multiple channels to disseminate the warning message – including visual 

means, audible means, and tactile means

5.2.4.2 A warning message should be repeated at least once, with some research 

advocating for message repetition of at least two times

Additionally, messages should be stated, in full, and then repeated, in full –

rather than repeating statements within the same message

Warning messages should be repeated at intervals, rather than consecutively

5.2.4.3 Warning messages should also be disseminated as early as possible

Face-to-face communication should accompany other audible or visual 

technologies

5.2.4.4 Messages should be disseminated using a combination of both push and pull 

technologies

Push communication is most important to use for alert signals as well as 

initial warning messages

6 Questions Left Unanswered

As mentioned in Section 2, the development of this guidance document has shed light on 

research findings that are either conflicting (between or within disciplines) or areas of the field 

that remain unexplored. This section represents a discussion of “the things we know we do not 

know.”

Conflicting research and guidance exist on the appropriate length of emergency messages. Some 

findings state that messages should be no more than 30 words long, a total of three sentences and 

last for approximately 9 seconds (Chandler 2010; Centers for Disease Control and Prevention 

2002). However, this guidance is often offered for events where the audience is not already 

paying attention, and in a disaster event, once people are made aware that something is going on, 

they are likely to stay tuned to information sources to find out more information. With that said, 
23

there is no additional guidance on a maximum message length for disaster-related warning 

information provided in building emergencies, especially for technologies where there is no 

fixed limit on message length (e.g., email, public address systems, etc). There is also no 

additional guidance on the appropriate length of audibly-provided pre-recorded messages versus 

live messages, although the guidance document does state the benefits of using live voice 

messages over a pre-recorded voice. Overall, messages should not be so long that they delay 

occupants taking protective action, but should be long enough to convey the appropriate 

information necessary to prompt response (i.e., the five topics listed in 5.2.1.1). 

An additional topic that requires further research is the ordering of warning message content. 

Traffic research provides one suggestion: the problem statement (or information on the disaster) 

should be provided first, followed by the location of the problem, then, ending with the action 

statement (i.e., instructions on what individuals should do in response to the problem). However, 

disaster research does not provide specific guidance on this to either confirm or refute this 

suggested message order. It will be important to test message order in future disasters to 

determine if message order matters and if so, the appropriate order for rapid-onset emergency 

warnings. 

No consensus was reached on the appropriate number of repetitions required for the emergency 

warning message. Most studies reported on the number of repetitions that would aid in recall; 

however, in a disaster, recall is less important than ensuring that the message is received (and 

paid attention to) by as many occupants in the building as possible. This guidance document 

suggests that the message is repeated at least one time, on an interval basis (rather than 

successive) to increase the number of individuals in the building who receive the message; 

however, more research should be performed on message repetition.

Finally, one finding on alerts warrants discussion: alerts should sound differently for different 

types of emergencies (U.S. Department of Justice 2010). This finding is not included in the 

guidance document because of the unnecessary burden this places on building occupants. 

Designing a communication system that sounds differently for each building emergency would 

require occupants to learn and remember a potentially complicated alert system. Using the 

alert/warning system described in Section 5, a building should use one consistent alert signal to 

get people’s attention to a building emergency situation, which should then be followed by an 

expertly crafted and tested warning message specific to the emergency. Currently, in buildings 

without a voice communication system, the fire alarm serves as both the alert and the warning 

system, and for this reason, fire researchers have advocated for a standardized fire alarm signal 

so that individuals from building to building understand what that signal means. However, if the 

building uses an alert system followed by an appropriate warning message, this is an even better 

way to get individuals to respond safely and effectively to the building emergency.

7 Future Work

The next step in this project is to develop emergency-specific guidance for message providers; 

i.e., guidance that will focus on the development of messages based upon building emergency 

type and technology used to disseminate the message. Message templates will be created that 
24

provide examples of how to formulate messages for different types of emergencies as well as the 

limitations associated with a range of technologies (e.g., voice communication versus text 

messaging). This is a very important section of the guidance document since many guidance 

document users (e.g., building emergency managers) will require examples of how to formulate 

messages to meet the varying needs of their building population. Common messaging practices 

across all buildings should enhance familiarity with message type and meaning, and thereby 

improve the effectiveness of alerts and warnings nationwide. In addition, guidance will also be 

provided on the importance of message testing and how to perform such tests after messages 

have been written. 
25

8 References

American National Standards Institute. (2011). ANSI/NEMA Z535.3-2011, Criteria for safety 

symbols. New York: American National Standards Institute.

Ball M, Bruck D. (2004, September). The Effect of Alcohol Upon Response to Fire Alarm 

Signals in Sleeping Young Adults. Proceedings of the Third International Symposium on Human 

Behaviour in Fire. Belfast, Northern Ireland. J Shields (Ed.), Interscience Communications, 

London, UK, 291–302.

Baker EJ. (1991, August). Hurricane Evacuation Behavior. International Journal of Mass 

Emergencies and Disasters, 9(2), 287-310.

British Standard BS 5839-8:2008. (2008). Fire Detection and Fire Alarm Systems for Buildings 

– Part 8: Code of practice for the design, installation, commissioning and maintenance of voice 

alarm systems.

Broersma M. (2009). Triggered codeswitching between cognate languages. Bilingualism: 

Language and Cognition, 12(4), 447–462.

Burt CDB, Henningsen N, Consedine N. (1999). Prompting correct lifting posture using signs. 

Applied Ergonomics, 30(4), 353-359.

Caird JK, Wheat B, McIntosh KR, Dewar RE. (1997). The comprehensibility of airline safety 

card pictorials. Proceedings of the Human Factors and Ergonomics Society 41st Annual Meeting 

Vol 2, 801-805.

Centers for Disease Control and Prevention. (2002, September). Crisis and emergency risk 

communication. Washington, DC: CDC.

Online course: http://emergency.cdc.gov/cerc/CERConline/index2.html.

Chandler, R. (2010). Emergency Notification. Santa Barbara: Praeger.

Conrad L. (1989). The effects of time-compressed speech on native and EFL listening 

comprehension. Studies in Second Language Acquisition, 11, 1-16.

Cooke M, Garcia Lecumberri, ML, Barker J. (2008, January). The foreign language cocktail 

party problem: Energetic and informational masking effects in non-native speech perception. The 

Journal of the Acoustical Society of America, 123(1), 414-427.

Covello V, Minamyer S, Clayton K. (2007, March). Effective risk and crisis communication 

during water security emergencies: Summary report of EPA sponsored message mapping 

workshops (Report No. EPA/600/R-07/027). Washington, DC: U.S. Environmental Protection 

Agency. 

http://cfpub.epa.gov/si/si_public_record_report.cfm?address=nhsrc/&dirEntryId=165863.
26

Creak J. (1997). About Viewing Distances. Means of Escape (Article 549). 

http://www.means‐of‐escape.com/articles/549/about‐viewing‐distances/

Drabek, T. E. (1986). Human System Responses to Disaster: An Inventory of Sociological

Findings. New York, NY: Springer-Verlag.

Drabek, Thomas E. 1969. “Social Processes in Disaster: Family evacuation.” Social Problems

16(3): 336-349.

Dudek CL, Ullman GL. (2001, November). Guidelines for changeable message sign messages: 

Annotated bibliography (DTFH61-96-C-00048). Texas Transportation Institute, College Station, 

TX.

Dudek CL, Huchingson RD, Stockton WR, Koppa RJ, Richards SH, Mast TM. (1978, 

September). Human factors requirements for real-time motorist information displays, Volume 1 

– Design Guide (U.S. Department of Transportation Report No. FHWA‐RD‐78‐5). Texas 

Transportation Institute, College Station, TX.

Edworthy J. (1998). What makes a good alarm? IEE Colloquium Digest on 'Medical Equipment 

Alarms: The Need, the Standards, the Evidence' (pp. 5-8). Ref. No 1998/432, The Institution of 

Electrical Engineers.

Edworthy J, Clift-Matthews W, Crowther M. (1998). Listener’s understanding of warning signal

words. In MA Hanson (Ed.), Contemporary Ergonomics 1998: Proceedings of the Annual 

Conference of the Ergonomics Society (pp. 316-320). London, UK: Taylor & Francis.

Groner, N. (2009). A Situation Awareness Analysis for the Use of Elevators During Fire 

Emergencies. In 4th International Symposium on Human Behavior in Fire: Conference 

Proceedings (pp. 61-72). London: Interscience Communications Ltd.

Gwynne, S. M. V. (2007). Optimizing Fire Alarm Notification for High Risk Groups. Quincy, 

MA: The Fire Protection Research Foundation.

Haas EC, Casali JG. (1995). Perceived urgency of and response time to multi‐tone and 

frequency‐modulated warning signals in broadband noise. Ergonomics, 38(11), 2313‐2326.

Haas EC, Edworthy J. (1996, August). Designing urgency into auditory warnings using pitch, 

speed, and loudness. Computing & Control Engineering Journal, 7(4), 193‐198.

Hablamos Juntos. Using Universal Symbols: Improving wayfinding through universal signage 

systems. (2007, March). Environment of Care News, 8-10.

Hellier E, Edworthy J, Weedon B, Walters K, Adams A. (2002, Spring). The perceived urgency 

of speech warnings: Semantics versus acoustics. Human Factors: The Journal of the Human 

Factors and Ergonomics Society 44(1), 1-17.
27

Huchingson RD, Koppa RJ, Dudek CL. (1978). Human factors requirements for real-time 

motorist information displays, Vol. 13: Human factors evaluation of audio and mixed model 

variables (Report No. FHWA-RD-78-17). Washington, DC: U.S. Department of Transportation.

ISO. (2011). ISO 7010:2011 Graphical symbols – Safety colours and safety signs – Registered 

safety signs. Pp. 124.

ISO. (2007). ISO 7001 Graphical Symbols – Public information symbols. Pp. 56.

ISO. (2004). ISO 16069 Graphical Symbols – Safety signs – Safety way guidance systems 

(SWGS). Pp. 51

Jamson SL, Tate FN, Jamson AH. (2005). Evaluating the effects of bilingual traffic signs on 

driver performance and safety. Ergonomics, 48(15), 1734-1748.

Jaynes LS, Boles DB. (1990). The effect of symbols on warning compliance. Proceedings of the 

Human Factors Society 34th Annual Meeting, Santa Monica, CA, 984-987.

Jin T. (2002). Visibility and human behavior in fire smoke. The SFPE Handbook of Fire 

Protection Engineering (3rd Edition), Eds: PJ DiNenno et al., National Fire Protection 

Association, Quincy, MA, pp. (2–42)-(2–54).

Kuligowski, E. D. (2011). Terror Defeated: Occupant sensemaking, decision-making and 

protective action in the 2001 World Trade Center disaster. Ph.D. Dissertation. Boulder, CO: 

University of Colorado at Boulder.

Kuligowski, E.D., S.M.V. Gwynne, K.M. Butler, B.L. Hoskins, and C.R. Sandler. (2012) 

Developing Emergency Communication Strategies for Buildings. Technical Note 1733, National 

Institute of Standards and Technology: Gaithersburg, MD. 

Kuhn BT, Garvey PM, Pietrucha MT. (1997). Model guidelines for visibility of on-premise 

advertisement signs. Transportation Research Record, 1605, 80-87.

Kunreuther, H. (1991). A Conceptual Framework for Managing Low Probability Events. 

Philadelphia, PA: Center for Risk and Decision Processes, University of Pennsylvania.

Latane, Bibb and John M. Darley. 1970. The Unresponsive Bystander: Why doesn’t he help?

New York, NY: Appleton-Century Crofts.

Lindell, M. K. and R. W. Perry. (2004). Communicating Environmental Risk in Multiethnic 

Communities. Sage Publications.

Mayhorn CB. (2005, November). Cognitive aging and the processing of hazard information and 

disaster warnings. Natural Hazards Review, 6(4), 165-170.

Melton AW. (1970, October). The situation with respect to the spacing of repetitions and 
28

memory. Journal of Verbal Learning and Verbal Behavior, 9(5), 596-606.

Mileti, D. S. and J. H. Sorensen. (1990). Communication of Emergency Public Warnings.

ORNL-6609, Oak Ridge: National Laboratory.

National Council on Disability. (2009, August). Effective emergency management: Making 

improvements for communities and people with disabilities. Washington, DC: NCD. 

http://www.ncd.gov/publications/2009/Aug122009

National Association of the Deaf. (n.d.). Emergency warnings: Notification of deaf or hard of 

hearing people. Silver Spring, MD: NAD(Author).

http://tap.gallaudet.edu/emergency/nov05conference/EmergencyReports/NADEmergency.doc

National Fire Protection Association. (2013). NFPA 72 US National Fire Alarm and Signaling 

Code. Quincy: National Fire Protection Association.

National Fire Protection Association. (2012). NFPA 170 Standard for Fire Safety and Emergency 

Symbols. Quincy: National Fire Protection Association.

National Fire Protection Association. (2010a). NFPA 72 US National Fire Alarm and Signaling 

Code. Quincy: National Fire Protection Association.

National Fire Protection Association. (2010b). NFPA 1600, Standard on Disaster/Emergency 

Management and Business Continuity Programs. Quincy: National Fire Protection Association.

National Research Council. (2011). Public response to alerts and warnings on mobile devices: 

Summary of a workshop on current knowledge and research gaps. Washington, DC: The 

National Academies Press.

Nilsson D, Frantzich H. (2004). Evacuation experiments in a smoke-filled tunnel. Proceedings of 

the 3rd Human Behavior in Fire Symposium, Belfast, UK, 229-238.

Nilsson D, Frantzich H, Saunders WL. (2009). Influencing exit choice in the event of a fire 

evacuation. Fire Safety Science- Proceedings of the Ninth International Symposium, 341-352.

Nilsson D, Frantzich H, Saunders W. (2005). Coloured flashing lights to mark emergency exits –

Experiences from evacuation experiments. Proceedings of the Eighth International Symposium 

on Fire Safety Science, 569–579.

Okabe, K. and S. Mikami. (1982). A Study on the Socio-Psychological Effect of a False Warning 

of the Tokai Earthquake in Japan. A Paper presented at the Tenth World Congress of Sociology, 

Mexico City, Mexico.

Quarantelli, E. L. and R. R. Dynes. (1972). “When Disaster Strikes (It Isn't Much Like What 

You've Heard and Read About)” Psychology Today 5(February): 67-70.
29

Perry, R. W., M. K. Lindell, and M. R. Greene. (1981). Evacuation Planning in Emergency 

Management. Lexington, MA: Lexington Books.

Phillips BD, Morrow BH. (2007, August). Social science research needs: Focus on vulnerable 

populations, forecasting, and warnings. Natural Hazards Review, 8(3), 61-68. 

Proulx G. (2001, May). Occupant behaviour and evacuation. Proceedings of the 9th 

International Fire Protection Symposium, Munich, Germany, 219-232.

Rea MS, Ouellette MJ, Clark FRS. (1985). Design considerations for egress signs based upon 

visibility through smoke. General Proceedings of AIA Research & Design 85, Architectural 

Applications of Design and Technology Research, American Institute of Architects, Washington, 

DC, 295-297; also (Report No. NRCC 25185), National Research Council of Canada, Ottawa, 

Canada.

Rousseau GK, Lamson N, Rogers WA. (1998). Designing warnings to compensate for agerelated changes in perceptual and cognitive abilities. Psychology & Marketing, 15(7), 643-662.

Sanders MM, McCormick EJ. (1993). Chapter 4: Text, Graphics, Symbols and Codes. In Human 

Factors in Engineering and Design (7th ed.) (pp. 91-128). New York: McGraw-Hill.

Schmidt JK, Kysor KP. (1987). Designing airline passenger safety cards. Proceedings of the 

Human Factors Society 31st Annual Meeting, 51-55.

Stout C, Heppner CA, Brick K. (2004, December). Emergency preparedness and emergency 

communication access: Lessons learned since 9/11 and recommendations. Deaf and Hard of 

Hearing Consumer Advocacy Network (DHHCAN) and Northern Virginia Resource Center for

Deaf and Hard of Hearing Persons (NVRC). 

http://tap.gallaudet.edu/Emergency/Nov05Conference/EmergencyReports/DHHCANEmergency

Report.pdf

Thomas IR, Bruck D. (2008). Strobe lights, pillow shakers and bed shakers as smoke alarm 

signals. Fire Safety Science-Proceedings of the Ninth International Symposium, Karlsruhe, 

Germany, 415-423.

Tierney, K. J. (2003). “Disaster Beliefs and Institutional Interests: Recycling disaster myths in 

the aftermath of 9-11.” Pp. 33-51 in Terrorism and Disaster: New Threats, New Ideas (Research 

in Social Problems and Public Policy, Volume 11), edited by Ted I. K. Youn. Bingley, UK: 

Emerald Group Publishing Limited.

Tierney, K. J., M. K. Lindell, and R. W. Perry. (2001). Facing the Unexpected: Disaster 

Preparedness and Response in the United States. Joseph Henry Press.

Timmons RP. (2009). Sensory overload as a factor in crisis decision-making and 

communications by emergency first responders. PhD dissertation, The University of Texas at 
30

Dallas.

Timmons RP. (2007, February). Interoperability: Stop Blaming the Radio. Homeland Security

Affairs, III(1), 1-17.

Ullman GL, Dudek CL, Ullman BR. (2005, September). Development of a field guide for 

portable changeable message sign use in work zones (Texas Department of Transportation 

Report No. FHWA/TX-06/0-4748-2). Texas Transportation Institute, College Station, TX.

U.S. Department of Justice. (2010, September). 2010 ADA Standards for Accessible Design. 

Washington, DC: DOJ (Author). http://www.ada.gov/2010ADAstandards_index.htm

Wang XH, Kapucu N. (2008). Public complacency under repeated emergency threats: Some 

empirical evidence. Journal of Public Administration Research and Theory, 18(1), 57-78.

Wang J-H, Cao Y. (2005). Assessing Message Display Formats of Portable Variable Message 

Signs. Transportation Research Record: Journal of the Transportation Research Board, 1937, 

113-119.

Wogalter MS. (2006). Purposes and scope of warnings. In MS Wogalter (Ed.), Handbook of 

Warnings (pp. 3‐9). Mahwah, NJ: Lawrence Erlbaum Associates, Inc.

Wogalter MS, Conzola VC, Smith‐Jackson TL. (2002). Research‐based guidelines for warning 

design and evaluation. Applied Ergonomics, 33(3), 219–230.

Young SL. (1991). Increasing the noticeability of warnings: Effects of pictorial, color, signal 

icon and border. Proceedings of the Human Factors Society 35th Annual Meeting, 580-584.