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.
- 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
LIC #ABC 123
- 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:
- AMBER ALERT
- 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.
Published By: US Department of Transportation
Source Date: 5/27/2004URL: http://www.ops.fhwa.dot.gov/TravelInfo/resources/cms_rept/cmspractices.pdf
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DMS, CMS, VMS, Changeable Message Signs, Variable Message Signs