Difference between revisions of "910.3 Dynamic Message Signs (DMS)"

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Dynamic Message Signs (DMSs) are stationary traffic control devices capable of displaying one or more alternative messages that provide travelers with real-time, traffic-related variable messages.  DMSs are used to warn, regulate, route and manage traffic.  A DMS shall not advertise or promote commercial events or entities and shall only display messages pertaining to highway safety or congestion reduction. A DMS shall not repeat [[903.4 Guide Signs|guide sign]], [[903.5 Regulatory Signs|regulatory sign]] or [[903.6 Warning Signs|warning sign]] messages.
Dynamic Message Signs (DMSs) are stationary traffic control devices capable of displaying one or more alternative messages that provide travelers with real-time, traffic-related variable messages.  DMSs are used to warn, regulate, route and manage traffic.  A DMS shall not advertise or promote commercial events or entities and shall only display messages pertaining to highway safety or congestion reduction. A DMS shall not repeat guide sign, [[903.5 Regulatory Signs|regulatory sign]] or [[903.6 Warning Signs|warning sign]] messages.
MoDOT operates DMSs through its transportation management centers (TMCs) in Kansas City ([http://www.kcscout.net/ KC Scout]), St. Louis ([http://www.gatewayguide.com/atis/index.html Gateway Guide]) and [http://www.ozarkstraffic.info/index.html Ozarks Traffic] in Springfield.  Each of these TMCs operates DMSs within its metropolitan coverage area.  The KC Scout and Gateway Guide TMCs also operate DMSs on the statewide rural I-70 and I-44 corridors, respectively.   
MoDOT operates DMSs through its transportation management centers (TMCs) in Kansas City ([http://www.kcscout.net/ KC Scout]), St. Louis ([http://www.gatewayguide.com/atis/index.html Gateway Guide]) and [http://www.ozarkstraffic.info/index.html Ozarks Traffic] in Springfield.  Each of these TMCs operates DMSs within its metropolitan coverage area.  The KC Scout and Gateway Guide TMCs also operate DMSs on the statewide rural I-70 and I-44 corridors, respectively.   

Revision as of 10:25, 19 January 2012

Dynamic Message Sign
Related Information
Changeable Message Signs (CMS)
Form and Guidelines
DMS Request Form
DMS Message Approval Board Guidelines

Dynamic Message Signs (DMSs) are stationary traffic control devices capable of displaying one or more alternative messages that provide travelers with real-time, traffic-related variable messages. DMSs are used to warn, regulate, route and manage traffic. A DMS shall not advertise or promote commercial events or entities and shall only display messages pertaining to highway safety or congestion reduction. A DMS shall not repeat guide sign, regulatory sign or warning sign messages.

MoDOT operates DMSs through its transportation management centers (TMCs) in Kansas City (KC Scout), St. Louis (Gateway Guide) and Ozarks Traffic in Springfield. Each of these TMCs operates DMSs within its metropolitan coverage area. The KC Scout and Gateway Guide TMCs also operate DMSs on the statewide rural I-70 and I-44 corridors, respectively.

910.3.1 National DMS Policy

Policies, standards, and guidelines at the national level are embodied in the ‘’Manual on Uniform Traffic Control Devices’’ (MUTCD) and a Federal Highway Administration (FHWA) memorandum. The primary sections in the MUTCD that address DMSs are Section 1A.14 "Abbreviations Used on Traffic Control Devices", Section 2A.07 "Changeable Message Signs" and Section 2E.21 "Changeable Message Signs".

The FHWA memorandum includes “Click It or Ticket Signs,” dated March 6, 2002, allowing the use of safety messages associated with a safety campaign, such as “Click It or Ticket” as long as they conform to sign design, location and spacing requirements, and do not block other regulatory, guide or warning signs.

910.3.2 MoDOT DMS Policy

910.3.2.1 Five Basic Requirements

Messages displayed shall convey pertinent information to assist motorists in their driving decisions. Messages shall be conveyed in a standard, non-confusing manner that allows drivers to both perceive and react to the information in a timely fashion. As stated in the MUTCD, DMSs, will be effective if five basic requirements are met.

1) Fulfill a need: Messages must only be posted to signs when there is a real need, and when the purpose is clear to the driver. If messages on DMSs are perceived to be unnecessary, drivers will begin to disregard all DMS messages.
2) Command Attention: The mere size of the signs themselves help to command driver attention, but the wording of messages can also contribute.
3) Convey a clear, simple meaning: At typical speeds, drivers have only a few seconds to notice, read and interpret posted messages. Proper composition and formatting is critical to conveying the most vital information in a manner that the driver will be able to assimilate. Consistency is an important aspect of this type of communication. Consistently composed and formatted messages become familiar to drivers and easier for them to comprehend quickly. Statewide messaging standards will improve the effectiveness of all DMS usage.
4) Command respect from travelers: Fulfilling a need and conveying a clear, simple meaning are important components of commanding respect. They must also display information that is accurate and timely. If drivers find information to be unreliable either because it is frequently in error or often out-of-date, they will ignore all DMSs.
5) Give adequate time for proper response: This requirement may be most pertinent to the placement of portable signs, but also speaks to the composition of messages. The desired response, in many cases, is simply for the driver to comprehend the information and become aware of possible congestion ahead. Messages that are poorly composed or contain too much information may be difficult for drivers to read in the few seconds they have while traveling at highway speed.

910.3.2.2 Responsibility for Operation of DMS

The district engineer shall authorize the use of all DMSs, both state and contractor-furnished, and may designate a person or persons to be responsible for the authorization of use, messages to be displayed, and the care, maintenance, and security of the DMSs. Access to the DMS shall only be given to responsible individuals. The district engineer shall ensure that efforts are coordinated such that motorists are informed of the most critical information based on priority of messages listed below. In the Kansas City, St. Louis and Springfield metropolitan areas, Scout, Gateway Guide and Springfield TMC operations staffs have been delegated the responsibility to operate the DMSs under their control.

The DMSs located on I-29, I-35 and I-70 in Districts 1, 2, 3, 4 and 5 are operated by the KC Scout TMC on a 24/7 basis. Districts 1, 2, 3 and 5 have the capability to operate the DMSs within their boundaries, but coordination with the KC Scout TMC is required.

The DMSs located on I-44, I-55, I-57 and US 60 in Districts 6, 7, 8, 9 and 10 are operated by the Gateway Guide TMC on a 24/7 basis. The Springfield TMC will have the capability to operate the I-44 DMSs located in Districts 7, 8 and portions of 9. Districts 7, 9 adn 10 will have the capability to operate the DMSs within their boundaries. Coordination of operations with the Gateway Guide TMC is required.

Districts without a TMC may also serve in a back-up role for their respective Interstate corridor in the event that the KC Scout, Gateway Guide or Springfield TMCs have other activities in their local metropolitan areas that prevent them from managing operations on the I-29, I-35, I-44, I-55, I-57, I-70 and US 60 corridors.

910.3.2.3 Message Priorities

The following message hierarchy determines what type of message has priority should more than one request be made to post a message to the same sign. The DMS messages shall be prioritized in the following order unless overridden by a supervisor:

1) Emergencies, such as evacuations or closures, required by MoDOT, the State Emergency Management Agency (SEMA), local law enforcement or the military.
Severe Weather
2) Hazardous and/or uncommon road conditions that require motorists to alter their driving, such as severe weather conditions, accidents, work zone activities or other incidents. Traffic operators should contact their floor supervisor when multiple incidents are taking place along the same route.
3) Traveler information and suggested alternative routes for delays and/or congestion caused by planned or unplanned events. Alternative routes are suggested with caution; sufficient trailblazing must be provided.
4) Child abduction alerts originating in the local area
5) Travel times
6) Child abduction alerts originating outside the local area
7) Ozone alerts
8) Advance date or time notice for scheduled incidents such as lane closures, road closures, moving operations or special events.
9) Approved standard public service messages associated with special campaigns (i.e. work zone awareness week, share the ride) or other public information that improves highway safety and reduces congestion. Approval should be coordinated through the TMCs for participation in such campaigns. Using the DMS Request Form, messages should be submitted, with suggested input from TMC staff, to Central Office Community Relations staff for endorsement. The DMS Message Approval Board will follow its own guidelines to approve or reject submitted messages.
10) When circumstances exist such that no message regarding safety or traveler information as defined by the previous listed priorities is warranted, Messages and Special Messages as outlined in EPG 910.3.2.16 Driver Safety Campaigns shall be displayed on all DMSs in Missouri. Messages shall be rotated regularly so that a variety of information is displayed to the traveling public. No message shall be excluded from the rotation unless otherwise approved by Traffic and Community Relations staffs.

Sometimes operators are faced with competing message needs when two or more incidents are simultaneously occurring on the freeway system downstream of a DMS. In such situations, operators must decide which of the incidents should be signed for, because it is not normally advisable to sign for both, unless a two-phase message is used. Procedures for posting two-phase messaging and situations that justify it are provided in EPG 910.3.2.14 Use of One-Phase and Two-Phase Messages. The following priority principles should be used in determining which competing incident should be signed for when a single phase is used:

  • Messages about the closer of two or more downstream incidents on the primary freeway should receive priority over the incidents that are further downstream, except as modified by Table 910.3.2.3 Suggested Message Priority for Downstream Major Accidents, below.
  • Messages about a downstream incident on the primary freeway should receive priority over incidents on downstream intersecting freeways or highways.

Suggested message priorities when a major accident occurs downstream of the closest incident on the primary highway are as shown in Table 910.3.2.3 below. District staff should be consulted prior to determining message priorities for incidents occurring on the I-29, I-35, I-44, I-55, I-57, I-70 and US 60 corridors.

Table 910.3.2.3 Suggested Message Priority for Downstream Major Accidents

Major Accident Occurs Downstream of: Give Message Priority to:
Major accident Upstream major accident
Minor accident Upstream minor accident
Roadwork with lane closure Downstream major accident
Roadwork with freeway closure Upstream roadwork
Incident (stalled vehicle, load spill, debris in roadway) requiring lane closure Downstream major accident
Incident requiring total freeway closure Upstream incident

910.3.2.4 Incident Verification

It is very important that operators verify an incident before posting an incident message on a DMS. The best source of verification is by viewing it with a CCTV camera, but if a CCTV camera view is not available, it must be verified by a reliable source. Examples of reliable sources are Motorist Assist Patrols, law enforcement agencies (i.e., MSHP, local sheriff and police departments) and MoDOT district staff or Construction/ Maintenance field staff. Media sources or the general public are not considered to be reliable sources for incident verification purposes. However, this unreliable information should be useful to operators in identifying information that needs to be explored further. Lines of communication need to be established between the above noted reliable sources and the TMCs. As part of this document, the contact numbers for each TMC as well as key district office staff are below:

MoDOT DMS Contact List

Testing a new DMS
HelpDesk (573) 751-5000
KC Scout (816) 622-6569
Gateway Guide (314) 275-1500
District 1 (816) 262-0367
District 2 (660) 651-7534
District 3 (573) 248-5961
District 4 (816) 622-6569
District 5 (800) 892-7332
District 6 (314) 275-1500
District 7 (417) 629-3461
District 8 (417) 766-3265
District 9 (573) 368-8631
District 10 (573) 380-9631

It is also important that operators continue to monitor and modify, as necessary, the incident message as the incident progresses. Where CCTV camera views are not available, operators need to maintain communication with the reliable sources at the incident scene to ensure that the current message is accurate and timely. Generally when CCTV cameras are not available, operators should attempt to get updated incident information from reliable sources every 15 minutes for incidents within the metropolitan areas controlled by the KC Scout and Gateway Guide TMCs and every 30 minutes for incidents along the I-29, I-35, I-44, I-55, I-57, I-70 and US 60 corridors.

910.3.2.5 Legibility and Visibility of DMS

Support. The maximum distance at which a driver can first correctly identify letters and words on a sign is called the legibility distance of the sign. Legibility distance is affected by the characteristics of the sign design and the visual capabilities of drivers. Visual capabilities, and thus legibility distances, vary among drivers.

For the more common types of DMS, the longest measured legibility distances on sunny days occur during mid-day when the sun is overhead. Legibility distances are much shorter when the sun is behind the sign face, when the sun is on the horizon and shining on the sign face, or at night.

Visibility is the characteristic that enables a DMS to be seen. Visibility is associated with the point where the DMS is first detected, whereas legibility is the point where the message on the DMS can be read. Environmental conditions such as rain, fog and snow impact the visibility of DMS and can reduce the available legibility distances. During these conditions, there might not be enough viewing time for drivers to read the message.

Guidance. DMS used on roadways with speed limits of 55 mph or higher should be visible from ½ mile under both day and night conditions. The message should be designed to be legible from a minimum of 600 ft. for nighttime conditions and 800 ft. for normal daylight conditions. When environmental conditions that reduce visibility and legibility are present, or when the legibility distances stated in the previous sentences in this paragraph cannot be practically achieved, messages composed of fewer units of information should be used and consideration should be given to limiting the message to a single phase.

910.3.2.6 Installation of a DMS

A DMS that is used in place of a static sign (such as a blank-out or variable legend regulatory sign) should be located in accordance with the provisions of Chapter 2A of the MUTCD. The following factors should be considered when installing other permanent DMS:

A. The DMS should be located sufficiently upstream of known bottlenecks and high crash locations to enable road users to select an alternate route or take other appropriate action in response to a recurring condition.
B. The DMS should be located sufficiently upstream of major diversion decision points, such as interchanges, to provide adequate distance over which travelers users can change lanes to reach one destination or the other.
C. The DMS should not be located within an interchange except for toll plazas or managed lanes.
D. The DMS should not be positioned at locations where the information load on drivers is already high because of guide signs and other types of information.
E. The DMS should not be located in areas where drivers frequently perform lane-changing maneuvers in response to static guide sign information, or because of merging or weaving conditions.

910.3.2.7 Message Creation and Termination

Although it is desirable to post an incident message based on complete and perfect information, situations often occur when the operator has received only limited information on the incident from reliable sources, particularly in the early stages of the incident. In these situations, operators should determine if there is at least general information about the incident location and type. If so, the operator should post a message with the information available and be prepared to modify the message as soon as more detailed information is received.

Incident messages should be terminated when all lanes are open and all emergency responders have left the scene. In addition, incident clearance messages should be posted for a short time after the incident clears if congestion remains at the scene. Procedures for posting incident clearance messages are provided in EPG 910.3.2.11 Incident Clearance Messages.

Congestion often exists at the incident scene after the incident has cleared and the incident clearance message is terminated. In those cases, it is necessary to post congestion messages that include either travel time or congestion location information. Procedures for posting congestion messages are available.

910.3.2.8 Message Formats

910. General Principles


Dynamic Message Signs shall be capable of displaying several messages in a sequence. Such messages shall be changed manually, by remote control or by automatic controls. DMSs shall display pertinent traffic operational and guidance information only, not advertising.

Because technology for DMS continues to advance, a specific standard for DMSs is not practical. Considerations that influence the selection of the best sign for a particular application include conspicuity, legibility, operational and maintenance of the DMS. This guidance applies to signs for use on freeway and expressway mainlines. It is recognized that similar signs might be used on ramps and at ramp terminals where smaller letter heights and the number of messages might differ from the provisions of this guidance.

DMS messages should present necessary information in the expected sequence that allows motorists to easily read, comprehend and rationally respond. Consistent formatting of the information enhances motorists’ expectations and reduces the time required to read and comprehend messages.

Messages should be provided to motorists that answer:

  • What happened?
  • Where?
  • What is the effect on traffic?
  • Who is the advisory for?
  • What is advised?

The basic message format to answer these questions can be reduced to the following elements:

  • Incident Descriptor informs the motorist of the problem (e.g., ACCIDENT, ROADWORK).
  • Closure Descriptor is used in place of the Incident Descriptor when all lanes of the facility or exit ramp are closed (e.g., I-70 CLOSED, EXIT 225 CLOSED).
  • Lanes Closed gives specific information about which lanes are closed (e.g., LEFT LANE CLOSED, 2 RIGHT LANES CLOSED).
  • Target Audience is used when the Action Message applies to a specific group of motorists rather than all motorists passing the sign (e.g., TRUCKS, STADIUM TRAFFIC).
  • Incident Location informs the motorist about the location of the problem (e.g., AT MAIN, PAST EXIT 15).
  • Closure Location specifically states the location of the freeway closure and is used in place of the Incident Location (e.g., AT MAIN, AT EXIT 15).
  • Effect on Travel informs the motorist of the severity of the problem in terms of delay or travel time and assists the motorist in making a decision whether to divert from the freeway or not (e.g., EXPECT DELAY, 30 MIN DELAY).
  • Action message informs the motorist what to do (e.g., USE OTHER ROUTES, FOLLOW DETOUR).

Although all of these elements provide critical information for the motorist, it is usually not possible to provide them all on the same sign due to limited space. Therefore, consider tradeoffs to determine which elements are to be included and omitted for different situations.

910. General Format

To the extent practical, the design and application of DMS should conform to the general principles of this article. Within the context of DMS, these practices should be followed for mainline freeway and expressway applications:

Use capital letters having a desirable letter size of 18 in. or a minimum letter size of 10.6 in. Signs should be limited to not more than 3 lines with not more than 20 characters per line.
No more than two displays should be used within any message cycle.
Each display should convey a single thought.
The entire message cycle should be readable at least twice by drivers traveling at the posted speed, the off-peak 85th percentile speed, or the operating speed.
Messages shall be centered within each line of legend. If more than one DMS is visible to travelers, then only one such sign shall display a sequential message at any given time.
A three-lined changeable message sign shall be limited to not more than two messages. Techniques of message display such as fading, rapid flashing, exploding, dissolving or moving messages shall not be used. The text of the message shall not scroll or travel horizontally or vertically across the face of the sign.
DMS shall automatically adjust their brightness under varying light conditions to maintain legibility.

The general DMS message format to be used statewide is as follows:

Line 1 Incident Descriptor, Closure Descriptor, Lanes Closed or Target Audience
Line 2 Incident Location, Closure Location
Line 3 Lanes Closed (if not used in Line 1), Effect on Travel, Action

Line 1 provides the information, intended to capture motorists’ attention, that they will soon be encountering a problem. Normally that information will be an Incident Descriptor or a Closure Descriptor and occasionally a Lanes Closed or Target Audience.

The following Incident Descriptors are acceptable for use on DMSs:

  • FOG

The Closure Descriptor should always be used on Line 1, in lieu of an Incident Descriptor, for road and exit closure incidents. The following Closure Descriptors are acceptable:

  • Route / Direction CLOSED

The Target Audience element should be on the first line if the message applies to a specific group of motorists passing the sign. The following examples of Target Audience messages are acceptable:

  • I-70 TRAFFIC

The Incident Descriptor should be omitted and replaced with the Lane Closed information on Line 1 if the Incident Descriptor cannot be identified (such as in the initial stages of the incident), if there are more important elements that need to be posted on the sign, or if messages need to be shortened to accommodate two-phase messages.

Line 2 provides location information for the incident or road closure. This location is provided in terms of the route and direction of the highway that the incident is on (if different than the road that the motorist is currently traveling on), the cross-street or highway closest to the incident (street/ highway name or exit number) and a preposition to describe the relative location of the incident to the cross-street/highway (BEFORE, AT or PAST). On the interstate corridors, mile markers are normally used for location descriptions rather than cross-streets or highways.

In determining whether to use street/highway names or exit numbers to describe incident or closure locations, street /highway names are normally more useful for motorists familiar with the area, and exit numbers are normally more useful for motorists, such as tourists, who are unfamiliar with the area. When signing for unfamiliar motorists in the Kansas City, St. Louis and Springfield metropolitan areas, the exit number of the closest cross-street/highway should be used to define the location rather than the mile marker of the incident.

When referring to interstates in the incident and closure locations, the prefix “I-” (e.g., I-70) should be used only if there is available space on the sign. Otherwise it should be omitted.

Line 3 provides specific information to the motorist about which lanes are closed (Lanes Closed) when this information has not already been placed on the first line, the severity of the incident in terms of delay or travel time (Effect on Travel), or what action the motorist is expected to take (Action Message).

Examples of acceptable Lanes Closed messages are:


The ONE LANE CLOSED message above should only be used on DMSs where the lane closure is more than a mile downstream of the DMS. Using this general message rather than a specific lane closure message prevents motorists from making unnecessary early lane changes.

Examples of Effect on Travel messages are:


Examples of Action Messages:

910. Message Length and Units of Information (MUTCD 2L.05)

Guidance. The maximum length of a message should be dictated by the number of units of information contained in the message, in addition to the size of the DMS. A unit of information, which is a single answer to a single question that a driver can use to make a decision, should not be more than four words.

The maximum allowable number of units of information in a DMS message is based on the principles described in this section, the current highway operating speed, the legibility characteristics of the DMS and the lighting conditions.

Each message shall consist of no more than two phases. A phase shall consist of no more than three lines of text. Each phase shall be understood by itself regardless of the sequence in which it is read.

When designing and displaying messages on DMS, the following principles relative to the message should be used:

A. The minimum time that an individual phase is displayed should be based on 1 second per word or 2 seconds per unit of information, whichever produces a lesser value. The display time for a phase should never be less than 2 seconds.
B. The maximum cycle time of a two-phase message should be 8 seconds.
C. The duration between the displays of the two phases should not exceed 0.3 seconds.
D. No more than three units of information should be displayed on a phase of a message.
E. No more than four units of information should be in a message when the traffic operating speeds are 35 mph or more.
F. No more than five units of information should be in a message when the traffic operating speeds are less than 35 mph.
G. Only one unit of information should appear on each line of the DMS.
H. Compatible units of information should be displayed on the same message phase.

Option. A unit of information consisting of more than one word may be displayed on more than one line. An additional DMS at a downstream location may be used for the purpose of allowing the entire message to be read twice.

The Tour of MO is a planned event

Guidance. If more than two phases would be needed to display the necessary information, additional DMS should be used to display this information as a series of two distinct, independent messages with a maximum of two phases at each location, in accordance with the provisions above.

When the message on a DMS includes an abbreviation, follow the provisions of Table 910.3.2.10.

910. Typical Messages

DMSs may be used to effectively reduce congestion caused by planned events or unplanned incidents such as excessive daily traffic, accidents, detours, construction delays, etc. Table 910. below provides some examples messages for DMSs used in the KC Scout and Gateway Guide TMC metro areas and the I-70 and I-44 corridor DMSs.

Table 910. Typical DMS Messages
Situation Metro TMC DMSs I-70 and I-44 Corridor DMSs
Primary Route Accident ACCIDENT ACCIDENT
Intersecting Route Accident ACCIDENT -
Primary Route Roadwork ROADWORK ROADWORK
Intersecting Route Roadwork ROADWORK -
Primary Route Incident (problem unknown) RIGHT LANE CLOSED RT LANE CLOSED
Intersecting Route Incident (problem unknown) RIGHT LANE CLOSED -
Primary/ Intersecting Route Closure I-35 SB CLOSED I-44 CLOSED
AT 75TH/EXIT 227 AT EXIT 118
Incident Clearance Messages ACCIDENT ACCIDENT
I-35 NB AT 127TH AT MM 162
Route Closure Clearance Messages ALL LANES OPEN ALL LANES OPEN
AT 75TH/EXIT 277 AT EXIT 118
Weather Messages FLOODING FOG
PAST EXIT 272 MM 185 TO MM188
or or

910.3.2.9 Acceptable Message Words and Terms

In determining the appropriate messages to post on DMSs, operators often have to choose words and terms for certain situations. To eliminate any confusion in the appropriate words and terms for these situations, the following list provides the acceptable words or terms to be used on DMSs on MoDOT-managed freeways and highways:


The term CRASH is currently the preferred term used by representatives of the safety community, although it is not a common term used by the general public. No human factors studies have been conducted that have determined motorists’ understanding and response times to messages containing the term CRASH in comparison to messages containing the term ACCIDENT. Accordingly, it has been concluded that ACCIDENT is the term more generally recognized by motorists and should be used.


Both terms are easily recognizable by motorists. The term PAST should be used because it is shorter and thereby takes less space.


The term EXIT should be used because it is generally better understood by motorists. RAMP is generally understood by motorists, but tends to have different shades of meaning for some motorists.


BLOCKED indicates that an incident is affecting a lane or lanes and response personnel have not yet arrived while CLOSED indicates that response personnel have arrived and are directing traffic out of the affected lane or lanes. MoDOT primarily uses CLOSED, and it is considered to be the acceptable term.

Days of Week vs. Calendar Dates

When notifying motorists of future roadwork or events, Days of the Week (e.g., MONDAY, THURSDAY) should be used while Calendar Dates should never be used. Accordingly, notifications of such events should only be placed for up to a week in advance of the event.

910.3.2.10 Acceptable Abbreviations

Because DMSs have limited available space, it is often necessary for operators to abbreviate words to place the appropriate message. KC Scout and Gateway Guide staff should develop standard abbreviations for street and highway names used in the areas controlled by these TMCs. In the development of these abbreviations, expected recognition by travelers in the area should be the primary consideration.

Acceptable abbreviations for common words used on DMSs are summarized in Table 910.3.2.10.

Table 910.3.2.10 Acceptable DMS Abbreviations

Word Abbreviation Word Abbreviation
Afternoon / Evening PM Monday MON
Alternate ALT Morning/late night AM
Avenue AVE North N
Bicycle BIKE Northbound NB
Boulevard BLVD Parking PKING
Center CNTR Pedestrian PED
Circle CIR Place PL
Crossing (Other than rail-hwy) XING Pounds LBS
Drive DR Right RT
East E Road RD
Eastbound EB Route RTE
Emergency EMER Saturday SAT
Entrance, Enter ENT Shoulder SHLDR
Expressway EXPWY South S
Feet FT Southbound SB
FM Radio FM Speed SPD
Freeway FRWY, FWY Street ST
Friday FRI Sunday SUN
High Occupancy Vehicle HOV Telephone PHONE
Highway HWY Temporary TEMP
Hospital H Thursday Thursday
Hour(s) HR Tons T
Information INFO Traffic TRAF
Junction/Intersection JCT Travelers TRAVLRS
Lane LN Tuesday -
Left LT US Numbered Route US
Maintenance MAINT Vehicles VEH
Miles(s) MI Warning WARN
Mile Marker MM Wednesday WED
Miles per hour MPH West W
Minute(s) MIN Westbound WB

910.3.2.11 Incident Clearance Messages

An incident clearance message is posted on the DMS when the incident has been cleared, all lanes have been opened to traffic and some residual congestion remains upstream of the incident scene. The message is only posted for about five minutes, after which the message is terminated or a congestion message is placed. The purpose of the incident clearance message is to inform approaching motorists that all lanes are open at the incident scene, but some congestion upstream of the incident scene may still exist. The incident clearance message is not necessary if there is no residual upstream congestion when the incident clears. Typical clearance messages are ACCIDENT CLEARED AT 7:10 AM (used on the Line 3 when ACCIDENT has been used on Line 1) and ALL LANES OPENED (used to replace the Road Closure Descriptor on Line 1). Examples of incident clearance messages are shown in Table 910. Typical DMS Messages.

910.3.2.12 Congestion Messages

Congestion is categorized as either recurring or non-recurring. Recurring congestion occurs at the same time and same location on a regular basis, usually because the traffic demand exceeds the roadway capacity at that location. Non-recurring congestion is congestion resulting from incidents, including special events, short-term roadwork or severe weather.

A congestion message is used to inform motorists that residual congestion still exists upstream of an incident after the incident clearance message has been terminated. Congestion messages can also be placed for recurring congestion when the congestion is more severe than normal, extends beyond the normal boundaries, or persists past the typical end of the peak period. Congestion messages should describe the limits of the congestion (e.g., METCALF to HOLMES) if the DMS is upstream of the congestion or the end of the congestion when the DMS is within the limits of congestion. Examples of congestion messages are shown in Table 910. Typical DMS Messages.

When congestion messages are posted on the rural corridor DMSs, it is critical that MoDOT field personnel provide KC Scout/ Gateway Guide operators timely updates on the congestion extent and limits. Updates should be provided at five- to ten-minute intervals.

When travel times are used and incorporated into the TMC software, as in the KC Scout and Gateway Guide TMCs, these travel time messages should be used in lieu of the congestion messages described above. These travel time messages provide valuable congestion information during incidents requiring two-phase messages and during other congested periods in both peak and non-peak periods. They also provide assurances to motorists when there is no congestion and the normal traffic conditions exist.

910.3.2.13 Weather Messages

Severe weather is not usually considered to be an incident, but weather-related messages should be displayed for the following conditions:

  • Roads are impassable due to flooding, snow, etc.
  • Ice or black ice on a specific roadway segment
  • Tornado sited in area near roadway
  • Low visibility due to fog in localized area

Examples of weather messages are shown in Table 910. Typical DMS Messages.

910.3.2.14 Use of One-Phase and Two-Phase Messages

Although operators should attempt to limit messages to a single phase, it is often necessary to use two phases to convey important information to motorists. When a two- phase message is warranted, it is critical to minimize the information on each phase to ensure that motorists will be able to read, comprehend and respond to both messages while driving at freeway speeds. The following situations will normally warrant the use of two-phase messages:

  • Travel time messages are placed as the second phase to an incident message.
  • Two downstream incidents are of equal priority as described in EPG 910.3.2.3 Message Priorities.

If two-phases are used, the following principles should be followed:

  • Under no circumstances should more than two phases be used.
  • Each phase should be understood by itself.
  • Compatible units of information should be displayed on the same phase.
  • Whenever possible, each phase should be limited to two lines. One way to reduce an incident message to two lines is to omit the Incident Descriptor on Line 1 and replace it with the Lanes Closed information.
  • Each phase should be displayed for a minimum of three, and preferably four, seconds.
  • Words or messages should never be flashed.

910.3.2.15 Child Abduction and Ozone Alert Messages

If a child abduction occurs and it meets the local AMBER Plan Program’s criteria for triggering an alert, a child abduction alert (AMBER Alert) message should be displayed on all stationary DMS in the area of the abduction, but should not create adverse traffic impacts such as queues, unexpected slowing of traffic, etc. If a higher priority message is needed on a DMS, then a child abduction alert messages should be alternated with that message until the child abduction alert is cancelled.

The TMCs will be responsible for coordinating with local and state police, as well as media to determine the need for the Amber Alert message.

1) The Amber Alert Message is to remain on the DMS until:
a) The Amber Alert has been cancelled by the local agency or state police
b) The TMC receives consensus from the local agency or state police to remove the message
c) the child is recovered.
2) TMCs will evaluate the need for the message on the DMS every 6 hours based on information received from law enforcement and/or media.

Both KC Scout and Gateway Guide have agreements with local law enforcement officials to post child abduction alerts for abductions that meet minimum criteria. The model used by both TMCs is the national AMBER (America’s Missing Broadcast Emergency Response) Program. The AMBER Program in the St. Louis metropolitan area is referred to as the SARAA (St. Louis Area Regional Abduction Alerts) Program.

Based on their agreements with the local law enforcement agencies, KC Scout and Gateway Guide TMCs use different messages for their child abduction alerts. KC Scout posts specific information on the abduction on its DMSs, while Gateway Guide posts only general information and provides information on where to go to get specific information. Typical messages used by these TMCs are as follows:

For KC Scout
For Gateway Guide
CALL 511

Child abduction alerts are posted on the rural corridor DMSs when the information from the KC Scout or Gateway Guide TMCs indicates that the abductor may be using one of the corridors or if local enforcement agencies on the corridors issue alerts for their local areas. If local alerts are issued, the messages to be posted should be coordinated with the local enforcement agency. Typical messages for corridor DMSs are:

For Corridor DMSs

Both metropolitan areas also have agreements with local agencies to place ozone alert messages when thresholds for the pollutant are exceeded. KC Scout has an agreement with the Mid-America Regional Council (MARC) and Gateway Guide has a similar agreement with Missouri Chapter of the American Lung Association. Typical messages used by these TMCs are as follows:

For KC Scout
For Gateway Guide

In order to maintain the existing local agreements, these messages should continue to be used in the respective Kansas City and St. Louis metropolitan areas, and standard messages for these Alerts will not be developed.

910.3.2.16 Driver Safety Campaigns

MoDOT has developed an Electronic Message Boards Communications Plan to provide safety and public service information on all MoDOT DMSs. Details of the plan are provided below:

Communications Goal

Develop informative messages that can be used on a regular basis to provide pertinent information and reminders to travelers.

Message Guidelines

The following messages will be rotated on all DMSs. These messages will provide variety and guard against message boredom. Higher priority messages, as provided in EPG 910.3.2.3 Message Priorities, will always override the general messages. Special messages will be placed on the DMSs as needed. Traffic staff will regularly monitor the DMS usage.





















Specialty Messages








Examples of safety messages include “SEAT BELTS BUCKLED?” and “DONT DRINK AND DRIVE”. Examples of transportation-related messages include “STADIUM EVENT SUNDAY/ EXPECT DELAYS NOON TO 4PM” and “OZONE ALERT CODE RED-USE TRANSIT”.

When a DMS is used to display a safety or transportation-related message, the message should be simple, brief, legible and clear. A DMS should not be used to display a safety or tranportation-related message if doing so would adversely affect the respect for the sign. “CONGESTION AHEAD” or other overly simplistic or vague messages should not be displayed alone. These messages should be supplemented with a message on the location or distance to the congestion or incident, how much delay is expected, alternative route or other similar messages.

910.3.2.17 On-Site Control of Changeable Message Signs

Portable Changeable Message Signs (CMSs) are normally used by MoDOT personnel or contractors to post information regarding construction or maintenance projects. To the maximum extent practicable, CMS messages should follow the provisions of EPG 616.3 Changeable Message Signs (CMSs).

Particularly in the Kansas City and St. Louis metropolitan areas, CMSs can be used to supplement the messages posted on the KC Scout and Gateway Guide DMSs. If these CMSs are to be useful in supplementing messages on DMSs, close coordination is needed between the TMC operators and those responsible for operating the CMSs to ensure that the DMSs and CMSs are not located too closely together and that that the messages don’t conflict.