Intelligent Roadway Information System

Incident DMS Deployment

Messages can be suggested for DMS from active roadway incidents. The attributes of the incident are used to make suggestions: impact, range, severity, and location on the freeway network.

Each message is composed of three parts: descriptor (what?), locator (where?) and advice (how?). Suggestions are only made if a match is found for all three parts.

If a suggested message is too wide for the sign, it will be abbreviated. If it cannot be shrunk to fit, it will be discarded.


Every incident is assigned an impact, based on which lanes are blocked or affected. If any lane is blocked, then one of the *lanes_blocked impacts is used. If any lanes are affected (partially blocked), the impact is one of the *lanes_affected values. Shoulder impacts are lower priority, first blocked then affected.

Impact Description
lanes_blocked Left & right lanes blocked (possibly all lanes)
left_lanes_blocked Left lane blocked, right lane open
right_lanes_blocked Right lane blocked, left lane open
center_lanes_blocked Center lane(s) blocked, left & right lanes open
lanes_affected Left & right lanes affected (possibly all lanes)
left_lanes_affected Left lane affected, right lane open
right_lanes_affected Right lane affected, left lane open
center_lanes_affected Center lane(s) affected, left & right lanes open
both_shoulders_blocked Left & right shoulders blocked, all lanes open
left_shoulder_blocked Left shoulder blocked, all lanes open
right_shoulder_blocked Right shoulder blocked, all lanes open
both_shoulders_affected Left & right shoulders affected, all lanes open
left_shoulder_affected Left shoulder affected, all lanes open
right_shoulder_affected Right shoulder affected, all lanes open
free_flowing No impact


Range is the distance from an upstream sign to the incident. There are four defined ranges, each with a number of freeway exits in between.

Range Exits Maximum distance
ahead 1.5 miles (0.75 miles picked)
near 0-3
middle 4-5
far 6-9

Searches for upstream signs will not continue on the opposite direction of the incident roadway.


Incident severity determines the maximum range and message priority. There are three severity values: minor, normal, and major.

Severity Maximum Range Message Priority
minor near high_2
normal middle high_3
major far high_4

Severity depends on how many lanes are blocked or affected, as well as the lane type at the incident location.

Impact Mainline CD/Exit Merge
more than half lanes blocked major normal minor
half or less lanes blocked normal minor
either shoulder blocked normal minor
any lane or shoulder affected minor


The descriptor determines the first line of each suggested message. The configurable descriptor table contains fields which are matched to the incident.

Field Description
Detail usually hazard detail: animal, debris, ice, etc
Lane Type mainline, exit, merge or CD road

If the detail field is blank, the descriptor will be used as a fallback for incidents which match the other two fields.


A matching locator determines the second line of a suggested message. The configurable locator table contains fields which are matched to the incident.

Field Description
Range from sign to incident: ahead, near, middle or far
Branched sign and incident on different roadways
Picked a pickable r_node is within 1 mile of the incident; its location can be used for locator tags

Locator Tags

Several MULTI-like tags are available for locators. These tags will be replaced with incident location information when composing a message. Tags should only be used if the locator's picked state matches.

Tag Picked Description
[locrn] Road name
[locrd] Road direction (NORTH, SOUTH, etc.)
[locmd] YES Location modifier (AT, NORTH OF, SOUTH OF, etc.)
[locxn] YES Cross-street name
[locmi] NO Miles from sign to incident

Road and cross-street names are converted to all capital letters.

Road Affixes

The road affix table determines how prefixes and suffixes are handled within [locrn] and [locxn] tags. Example suffixes are AVE and RD.

Field Description
Affix road prefix / suffix string
Prefix true for prefix, false for suffix
Fixup string to replace affix for sign message display
Allow Retain true if retaining affix is allowed without fixup


A matching advice determines the third line of a suggested message. The configurable advice table contains fields which are matched to the incident.

Field Description
Impact incident impact
Lane Type mainline, exit, merge or CD road
Range from sign to incident: ahead, near, middle or far
Open Lanes count of non-shoulder lanes not impacted by incident
Impacted Lanes count of non-shoulder lanes impacted

Rows where open and / or impacted lanes are specified will be matched in preference to rows where they are not.

Sign Restrictions

Dedicated purpose signs normally cannot be used for incidents. An exception is #Tolling signs — they are used if these conditions are met:


Deployed signs will be linked with the incident. If a sign message is later changed by an operator, it will keep the incident link unless the descriptor (first line) is changed.


If any signs are linked with an incident when an update is logged, the device deploy logic will be checked again. If there are suggested changes, the device deploy form will appear. All changes will be listed in the form, including new devices and devices to be blanked.


When a major severity incident is cleared, a new message will be sent to each linked sign. The descriptor and locator will be the same, but advice will be taken from the incident_clear_advice_multi system attribute. The cleared message will be deployed with low_sys message priority for 5 minutes.