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INFORMATION and ACTION: Dynamic Message Sign (DMS) Recommended Practice and Guidance

Date: July 16, 2004



(for) Jeffrey F. Paniati /s/Jeffrey A. Lindley (Director, HOTM-1)

Reply to

Attn. of: HOTM-1



Division Administrators

Directors of Field Services

Resource Center Managers

Federal Lands Division Engineers



Over the years, transportation agencies have invested millions of dollars to acquire and install dynamic message signs (DMS) as ways to provide information to motorists en-route. Based on the numbers of DMS reported in the 2002 Intelligent Transportation Systems (ITS) deployment tracking database, at least $330,000,000 have been spent on DMS. During adverse road conditions, traffic incidents and construction the signs have been used very effectively. The DMS have also been valuable assets for child abduction (AMBER) alerts and national security messages. But, we have also seen too many instances where the DMS are underutilized or providing generic information even though traffic conditions are deteriorating. As noted in Christine Johnson's December 21, 2001, memorandum, "Congestion Ahead Messages" (enclosed for ready-reference), there are many reasons why ineffective or questionable messages are displayed. However, regardless of the underlying reasons, the public sees only an ineffectively used, expensive piece of technology.


I want to reiterate and reinforce a couple of items noted in the December 2001 memorandum. Better DMS messages, based on travel times, can be displayed with the information currently available. There is no need to wait for more complete or "full" data coverage to begin providing better information to motorists. I also ask that you raise the importance of this issue regarding effective messages on DMS in discussions with your State, and furthermore, raise the issue of providing travel time messages on DMS. Our goal should be to have travel time information as the default information available to motorists throughout the day. A "dark" or blank DMS is a transportation investment that is not being fully utilized. We should be asking why is it dark and what will it take to get travel times posted on an ongoing basis. Furthermore, no new DMS should be installed in a major metropolitan area or along a heavily traveled route unless the operating agency and the jurisdiction have the capability to display travel time messages.


Recommended Practice


An examination of databases and a sampling of locations reveal at least 12 metropolitan areas that are providing travel time messages on DMS. But at least 25 other metropolitan areas are gathering travel time data and have DMS deployed. A list of all of these metropolitan areas is attached for your reference. We want to encourage the locations that are not currently providing travel time messages on DMS to investigate doing so. Travel time messages are not appropriate for every location, but they have proven successful in regions or corridors that experience periods of recurring congestion - congestion generally resulting from traffic demand exceeding available capacity and not caused by any specific event such as a traffic incident, road construction or a lane closure. The DMS can provide dynamic travel time information instead of providing generic messages such as "congestion ahead" or "stay alert."


While travel time messages may be overridden by traffic incident or road construction messages, they can provide valuable motorist information in conjunction with the event messages, as well as after the incident or construction has been cleared if there is residual congestion. Also, special events that typically generate traffic demand that exceeds capacity - fairs, concerts, sporting events - provide additional opportunities for providing travel time information to motorists.


The areas that have been providing travel time messages have found solid public support for the messages. Their experiences have provided a number of recommendations summarized here from the guidance report referenced below.


Guidance Report


We have seen from the growing use of DMS for posting AMBER Alert, national security and other non-typical messages that DMS are viewed as valuable roadway "real estate" for providing information. Because of the increased use of DMS for non-typical messages over the past year, we have developed a guidance report that deals with three specific types of messages: AMBER (America's Missing: Broadcast Emergency Response) Alert messages, national security or emergency messages, and travel time messages. The report is complete and available electronically at The goal of the report is to help ensure that DMS are used appropriately and safely, and to increase the credibility of DMS messages with motorists.


The report is based on interviews and surveys of selected States and locations to gather their successful practices when providing these types of messages. The report also drew heavily from prior research work including very recent guidance from the Transportation Management Centers Pooled Fund Study dealing with agency policies and procedures governing DMS operations. This fundamental guidance includes how to develop and display messages, and how to operate DMS. Additional information about the TMC Pooled Fund Study and this project is available at:


The report notes that messages related to national security or emergencies are relatively rare and typically directed by State executives. Existing guidance for DMS operations has proven successful in most locations in ensuring that only messages relevant to motorists and requiring actions by motorists are displayed.


Regarding AMBER Alert messages, the report notes that providing AMBER Alert information on DMS is the result of requests from the law enforcement agency that is responsible for issuing the AMBER Alert. There has been significant variety in the AMBER Alert messages that have been displayed, from the "AMBER ALERT / CALL 9-1-1" message that resulted in a flood of calls to the 911 center, to the three panel display with full victim and vehicle description, license plate number, and 10-digit telephone number to call in sightings. While it may be impractical to develop specific message standards because of the variety in DMS physical design, the fundamentals of constructing dynamic messages apply. We recommend against using the phrase "AMBER Alert" as part of the message to avoid confusion with security or other types of alerts that may be posted; however, we do suggest that when the size of the DMS permits, "AMBER" be included with the message to take advantage of the national branding resulting from the national AMBER Alert program. An example message might read, "AMBER CHILD ABDUCTION" or "AMBER ABDUCTION."  Also, because of the limited amount of information that can be safely conveyed by the DMS, AMBER Alert messages should direct the public to other information sources where they can get more details. Examples of other sources include local media, highway advisory radio and 511 travel information telephone services. But even when used in cooperation with other information sources, it is valuable to include some minimal but specific information about the suspect vehicle so that motorists who do not have immediate access to the other information sources can still provide assistance toward recovering abducted children. The license plate number is suggested as the most useful specific information for identifying suspect vehicles.




As stated in the January 19, 2001, Policy Memorandum, "Use of Changeable Message Sign (CMS)" ( and reiterated by subsequent policy memorandums in 2002 ("AMBER Alert Use of Changeable Message Sign" - and 2003 ("Use of Changeable Message Sign for Emergency Security Messages" -, FHWA supports the use of dynamic message signs as traffic control devices to safely and efficiently manage traffic by informing motorists of roadway conditions and required actions to perform. It is FHWA policy that the appropriate use of DMS and other types of real-time displays should be limited to managing travel, controlling and diverting traffic, identifying current and anticipated roadway conditions, or regulating access to specific lanes or the entire roadway. But it is also important that these assets and investments be used more effectively to provide motorists with meaningful and useful information. Providing travel time information is an excellent method of notifying motorists about current conditions in a manner that can be easily interpreted and understood.


If you have any questions or need further information, please contact Bob Rupert at (202) 366-2194 or











ACTION: "Congestion Ahead" Messages                                         December 21, 2001



Christine M. Johnson /s/ Christine M. Johnson

Program Manager, Operations                                                            HOTM-1

Director, ITS Joint Program Office


Division Administrators



The launch this week of 511 traveler information telephone service in Utah reminds us of the interest of the public in knowing more about travel conditions, and of the importance of traveler information to the operations of transportation systems. One of the more visible methods for providing information to travelers is the changeable or dynamic message sign (DMS). According to the ITS Deployment Tracking database, there are nearly 2,000 DMS installed in the major metropolitan areas with hundreds more planned by 2005.


We've all seen the good things that these signs can do, providing road closure notices, warning of hazardous conditions, and, in a few places around the country, providing travel times. We've also seen the pictures in the newspapers showing stopped traffic under a sign displaying a message that says, "Congestion Ahead" or "Expect Delays" or, worse yet, "Normal Conditions." These types of messages, that do not offer meaningful or useful information to travelers, contribute to the erosion of the public's trust in these systems and of the information they provide. As I noted in a memorandum to the Pennsylvania Division earlier this year (available under FHWA Directives and Policy Memorandums at, "Inaccurate, incomprehensible, or inappropriate information displayed on a [DMS] can ... cause motorists to question the credibility and ignore all [DMS] messages."


There are many reasons why ineffective or questionable messages are displayed. They may be initial, computer-generated messages that are being investigated by system operators. The library of messages that is available to operators or computer systems may not be robust enough to provide more detailed information. Perhaps these are the most accurate messages that can be displayed given the imprecise or sketchy data that is available from the roadway. Or there may be agency policies that preclude offering messages with greater details or preferred actions. Regardless of the underlying reasons, the public sees only an ineffectively used, expensive piece of technology. Secretary Mineta has been among those that have expressed frustration with this seeming waste of resources.


We need to work closely with our partners in the operating agencies to ensure that they are designing and using their DMS effectively. There are a number of activities underway to try to help agencies provide better information. A number of these efforts are part of a Transportation Management Center (TMC) pooled fund study that has 21 participants including 18 states, the District of Columbia, the I-95 Corridor Coalition, and FHWA. Additional information about the TMC pooled fund study is available at The pooled fund study is initiating a project related to changeable message sign practices, policies and procedures that will produce guidelines to help agencies select appropriate messages. The pooled fund study is also supporting a project in 2002 to develop guidance for TMC operational concepts and performance requirements that should help agencies better recognize how traveler information and transportation management work together.


Another FHWA project is addressing consistency of text-based messages, including DMS. This may result in more robust message libraries for use by operators and computer programs. Other projects include researching techniques for combining (or fusing) various data for use by traveler information systems, resulting in a best practices report; and development of an extensible mark-up language (XML) vocabulary for traveler information that will allow information to be exchanged among agencies more easily. These types of efforts can help create and exchange better traveler information that may be useful in displaying messages on DMS.


Finally there is an effort to encourage increased data collection about traffic and transportation networks. This "infostructure" may result in improved and more detailed knowledge about how transportation systems are functioning. This information could then help create more useful messages for display on DMS. However, it is also important to note that better DMS messages can already be displayed with the information currently available. There is no need to wait for "full" data coverage to begin displaying useful information to the traveling public.


We ask that you take the following actions:


If you or your staff have any questions or wish additional information, please contact Bob Rupert at or (202) 366-2194.



cc:       HOA-1


            Directors of Field Services

            Resource Center Directors



Metropolitan Areas Providing Travel Time Messages on Dynamic Message Signs


Metropolitan Areas with Travel Time Data [1]

[1] From 2002 ITS Deployment Tracking database (data no longer available)

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