IRIS
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.
Impact
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
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 | — |
- Only one exit is counted for each interchange (for example, the off-ramps of a cloverleaf)
- Intersections are counted as if they were exits
- Exits from a CD road are not included in the count
Searches for upstream signs will not continue on the opposite direction of the incident roadway.
Severity
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 |
— | — |
Descriptor
The descriptor determines the first line of each suggested message. The configurable descriptor table contains fields which are matched to the incident.
| Field | Description |
|---|---|
| Incident type | CRASH, STALL, ROAD WORK or HAZARD |
| 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.
Locator
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 |
- For the
[locrn]and[locxn]locator tags, matched affixes are replaced with the fixup value
Advice
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:
- Sign and incident are on the same roadway (not branched)
- Sign is less than 1 mile upstream of the incident
- Left lane impacted:
lanes_blocked,left_lanes_blocked,lanes_affectedorleft_lanes_affected
Linking
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.
Updates
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.
Clearing
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.