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Current Alert and Warning Systems and Their Characteristics
The alert and warning ecosystem includes a network of government and industry-supported systems and dissemination channels. A brief history of government-mediated systems is outlined below as well as a discussion of the characteristics of each dissemination channel.
GOVERNMENT-MEDIATED ALERT AND WARNING SYSTEMS
Alert and warning systems have evolved over time to reflect new types of hazards or technologies, moving from various television and radio broadcast technologies to now include cell broadcast. (See Figure A.1 for the evolution of emergency broadcasting.) However, this evolution has occurred very slowly and has often stemmed from a major hazards event. Furthermore, alert and warning systems have not kept up with new technologies. For example, the 2006 Warning, Alert, and Response Network (WARN) Act prompted the first significant changes to national alerting systems since the mid-1990s.
The WARN Act in combination with Executive Order 134071 created the Integrated Public Alert and Warning System (IPAWS) and the Wireless Emergency Alerts (WEA) system then known as the Commercial Mobile Alert System (CEAS). The goal of this system was to integrate various alerting systems, the Emergency Alert System, National Warning System, WEA system, and the National Oceanic and Atmospheric Administra-
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1 Executive Order. No. 13407, 2006, pp. 1226–1228.
tion (NOAA) Weather Radio All Hazards into one modern network. The new system also looks to take advantage of newer forms of communication, such as cellular telephony, satellite and cable television, and mobile devices. Additionally, IPAWS allows for alerts to be originated by various government organizations and officials at the federal, state, local, and tribal level, and allows a single message to be transmitted to the various alert platforms.
The IPAWS platform simultaneously allows alert originators (AOs) to submit alerts to a server that aggregates and disseminates these alerts to the proper systems. Figure A.2 illustrates the IPAWS architecture. An XML-based data format, Common Alerting Protocol (CAP), normalizes alert data across hazards, jurisdictions, and warning systems. CAP data structure is compatible with existing alert formats but also builds on new capabilities, such as those needed for WEA. IPAWS significantly updated geotargeting capabilities. Older alert systems relied on FIPS codes that were assigned by county or urban area. IPAWS allows flexible geotargeting that can more narrowly target areas using GIS data by entering polygon coordinates to outline the at-risk area. Other new capabilities include multilingual and multiaudience messaging; phased and delayed effective times and expirations, enhanced message update and cancellation features, template support, digital encryption and signature capabilities, and facilities for digital images, audio, and video.
As an example, consider the following emergency situation: A storm produces large amounts of rain, water-level sensors in a local creek in Boulder County indicate rapid onset of a flooding event, and the National Weather Service (NWS) issues a flash flood warning for a polygonal area that the storm will hit hardest. The local emergency management coordinator, who serves as an AO, crafts an alert. The AO submits this alert (in the form of a CAP message that includes the type of event and area impacted) to IPAWS, which then, after authenticating the message, sends it out to the appropriate Emergency Alert System (EAS), WEA, NOAA radio, and other disseminators. In the case of WEA, the cell carriers would use cell broadcast to transmit the alert to a set of cell towers that correspond to the specified area.
Emergency Alert System
EAS is a national warning system originally put in place to enable the president to speak to the United States within 10 minutes and largely used today as a way to alert the public of hazard events. EAS messages are transmitted via AM, FM, broadcast television, cable television, land mobile radio services, and more recently, digital television, satellite television, digital cable, and satellite and digital radio. Messages, which have
no length limits, must contain a Specific Area Message Encoding (SAME) header—which contains originator, a short description of the event, date/time issues, and identification of originating station—an attention signal, an audio announcement, and a digitally encoded end-of-message marker. There are currently 80 types of events for the use of EAS.
Wireless Emergency Alerts
As required under the WARN Act, the Commercial Mobile Service Alert (the original name for WEA) Advisory Committee (CMSAAC) was established in late 2006 by the Federal Communications Commission (FCC) to engage stakeholders in the development of initial policy and procedures for one component of that national system—the use of cellular telephones for alerts. CMSAAC, composed of representatives from service providers, handset vendors, emergency personnel, and industry groups, issued its first report in 2007, defining the CMAS’s basic system architecture and establishing technical standards and operating procedures.2
Messages were restricted in length to 90 characters and the inclusion of URLs was explicitly prohibited. Messages were divided into three categories, presidential alerts, imminent threat alerts, and child abduction alerts. WEA is an opt-out system; cellular customers receive imminent threat alerts and AMBER Alerts, unless they opted out, and cannot opt out of presidential alerts.
Carrier participation is voluntary; to date the major cellular carriers have signed on to the program. WEA-compatible handsets use a special alert tone for WEA messages—to draw attention to the messages and to distinguish them from other messages. This tone overrides the normal ringer-volume settings. A unique vibration cadence is also used to reach hearing-impaired users.
The message format defined for WEA was based on the Common Alerting Protocol.
WEA uses cell broadcast technology known as short message service-cell broadcast (SMS-CB) to transmit messages. Cellular broadcast offers two principal advantages over SMS. First, a single broadcast message can reach each active cell phone within range of a given cellular tower, reducing the network capacity required for message delivery compared to that required for sending messages to each subscriber. Moreover, because
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2 The recommendations of the CMSAAC appear in its draft report: Commercial Mobile Service Alert Advisory Committee, 2007, Commercial Mobile Alert Service Architecture and Requirements, PMG-0035, FCC, Washington, DC; and in Federal Communications Commission, 2008, Notice of Proposed Rule Making on the Matter of Commercial Mobile Alert System, Public Safety Docket No. 07-287, Washington, DC.
cellular broadcast uses a data channel separate from that used for other messages and calls, it is unaffected by network congestion.
A September 2016 update to the rules for WEA provided significant enhancements,3 including the following:
- Increase message length to 360 characters for 4G long-term evolution (LTE) and future networks.
- Allow embedded phone numbers and URLs to be included.
- Deliver to a more narrowly defined geographic area.
- Establish a new class of alerts, public safety messages, to convey essential and recommended actions (e.g., emergency shelter locations or boil water order).
- Require providers to support transmission of Spanish-language alerts.
Opt-In Alert and Warning Systems
Jurisdictions have leveraged the ability to deliver messages via SMS and email by purchasing third-party systems that allow for opt-in registration. Emergency management organizations market these systems to the public, who register to receive either SMS or emails about a range of topics. These types of systems are also often used for location-of-interest alerting, for example, school systems and universities; some utilities also use these systems to alert subscribers of system outages. Both SMS-capabilities as well as email only reaches those who register ahead, which limits the reach of these systems.
OTHER ALERT AND WARNING SYSTEMS
Several private organizations have built various alert and warning systems within their own communication networks. These include various weather applications that allow users to receive notifications when weather alerts are issued by the NWS or Google.org’s overlay of various alerts and warnings on its maps.
CHARACTERISTICS OF EMERGENCY MESSAGE DISSEMINATION CHANNELS
There is a wide variety of alert and warning dissemination channels available to public message providers in the United States. These are
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3 Federal Communications Commission, FCC 16-127, adopted September 29, 2016, https://apps.fcc.gov/edocs_public/attachmatch/FCC-16-127A1.pdf.
listed in Table A.1 and evaluated in terms of the speed at which each can deliver the message, the coverage area that each channel reaches, the degree to which the channel reaches everyone versus only people in focused locations, and the extent to which each channel can provide detailed information in the following table. An inspection of this table illustrates that each communication channel has both advantages and shortcomings. The key shortcoming of WEA messages (limited to 90 characters at the time the table was prepared) is that those messages lacked message comprehensiveness.
TABLE A.1 Characteristics of alert and warning dissemination channels in the United States
| Dissemination Channels | Speeda | Coverageb | Concentrationc | Message Comprehensivenessd |
|---|---|---|---|---|
| Route alerting | Slow | Limited | Concentrated | High |
| Loudspeakers and public address (PA) systems | Fast | Limited | Concentrated | Medium |
| Wireless Emergency Alerts (WEA) | Very Fast | Widespread | Dispersed | Very Low |
| Wireless communications (SMS) | Very Fast | Widespread | Dispersed | Very Low |
| Radio | Moderately Fast | Widespread | Dispersed | High to Low |
| Television broadcast | Moderately Fast | Widespread | Dispersed | Very High to Medium |
| Television message scrolls | Moderately Fast | Widespread | Dispersed | Low |
| Newspaper | Very Slow | Widespread | Dispersed | Very High |
| Dedicated tone alert radios | Very Fast | Limited | Concentrated | High |
| Tone alert and NOAA Weather Radio | Fast | Widespread | Dispersed | High |
| Text Telephone (TDD/TTY) | Fast | Widespread | Dispersed | Low |
| Reverse telephone distribution systems | Fast | Limited | Dispersed | High |
| Audio sirens and alarms | Fast | Limited | Concentrated | Very Low |
a The rapidness of the system to reach its targeted audience ranges from Very Fast (less than 10 minutes to Slow (greater than 60 minutes).
b Coverage is the size of the area that can be reached by the channel (Widespread, a large area, or Limited, a small area).
c Concentration is the degree to which the people that the channel reaches are co-located or dispersed (Concentrated, the message is delivered to targeted locations only or Dispersed, the message has the potential to reach everyone).
d Comprehensiveness, or the ability to convey the content needed for effective response classes, used in this table are as follows: Very Low (alerting only); Low (very little information conveyed); Medium (many but not all essential contents conveyed); High (all relevant content conveyed); Very High (all relevant content conveyed with enhanced graphics).
SOURCE: J. Sorensen and D. Mileti. 2014. Protective Action Initiation Time Estimation for Dam Breaches, Controlled Dam Releases, and Levee Breaches or Overtopping. Paper prepared for U.S. Army Corps of Engineers Institute for Water Resources, Risk Management Center. Davis, CA.
