Strike a balance between CMS content and the driver's ability to read at 65 mph when posting AMBER alerts.

The experience of several states regarding AMBER alerts.

United States

Background (Show)

Lesson Learned

AMBER alerts, America’s Missing: Broadcast Emergency Response (AMBER alerts), have been used for the past several years to help find abducted children by asking the public to be on the lookout for a particular type of vehicle through Changeable Message Sign (CMS) messages and other forms of media. This lesson addresses the experiences and best practices with regard to posting AMBER alerts on CMS and striking a balance between sign content and the driver's ability to read at high speeds.
  • Recognize the limitations of drivers’ to decipher messages while traveling at high speeds. The study noted that states and jurisdictions are still refining their policies and contents of the AMBER alert messages, however, it was suggested that the majority of respondents indicated that three lines are used to alert the public to a child abduction. The three line message is recommended to be displayed over two pages on a CMS type display. Redundancy can also improve driver retention of information and reduce driver work load. An example of a CMS display is shown below:
    Page I
    CALL 911

    Page II
    LIC #ABC 123
    CALL 911
    The only information that changes in this message is the second line of the two pages. One noted difference by Caltrans District 12 is the inclusion of the State in which the license plate is issued in lieu of the license plate number. Decision makers in that area believe that drivers cannot remember the lengthy string of numbers and letters of a license plate, but could note a state in which the plate was issued.

    Some jurisdictions consider that a license plate number is too much information for a motorist to absorb while driving at freeway speeds, and instead prefer to advise motorists to tune to local news radio to obtain more information.
  • Create messages with time constraints in mind. The majority of facilities that have CMS are high speed; as a result, it is recommended that short, concise messages be presented to drivers when posting AMBER alerts. CMS on interstates should use one page only; information more than one page in length exceeds the driver's capacity to absorb the information and drive safely. As indicated in the lesson above, many jurisdictions use a two page message with redundancy between the pages to help retain the information. Agencies should take these recommendations into account when developing AMBER Alert policies and messages.
  • Avoid vague messages which can result in false calls to 911. It has been recognized that vague information is confusing to users of the facility and results in little worthwhile information. Washington DOT at one time issued an alert with just the following limited information on the CMS:
    CALL 911
    The result was a flood of calls from motorists who were unsure of what action to take. This message format was not recommended for future use.

The overall response to AMBER Alerts is consistently positive nationwide. The public sees the use of CMS for AMBER Alerts as a very valuable use of the equipment. This lesson suggests that messages should be constructed to be as short as possible while still conveying pertinent information to the motorists. This helps keep the traveling public safe while providing a public service that may save a life. Striking a balance between message content and the driver's ability to read and retain information at high speeds contributes to achieving ITS goals including safety, efficiency, and customer satisfaction.

Lesson Comments

No comments posted to date

Comment on this Lesson

To comment on this lesson, fill in the information below and click on submit. An asterisk (*) indicates a required field. Your name and email address, if provided, will not be posted, but are to contact you, if needed to clarify your comments.


Amber, Emergency, and Travel Time Messaging Guidance for Transportation Agencies

Author: PBS&J/Battelle

Published By: US Department of Transportation

Source Date: 5/27/2004

URL: http://www.ops.fhwa.dot.gov/TravelInfo/resources/cms_rept/cmspractices.pdf

Other Lessons From this Source

Lesson Contacts

Lesson Contact(s):

Aimee Flannery, Ph.D., P.E.
George Mason University

Lesson Analyst:

Firoz Kabir


Average User Rating

0 ( ratings)

Rate this Lesson

(click stars to rate)


None defined


United States

Systems Engineering

Show the V

None defined

Goal Areas



DMS, CMS, VMS, Changeable Message Signs, Variable Message Signs

Lesson ID: 2005-00133