IRIS
Intelligent Roadway Information System
RWIS
Road weather information system (RWIS) messages can be displayed on DMS, using data collected from weather sensors.
RWIS Action Tags
Warning messages for road weather conditions can be displayed on DMS using
DMS actions. An [rwis_ … ] action tag in the message pattern will
cause a message to be displayed when the specified weather condition is
detected. The tag has the following format:
[rwis_ condition,level ]
| Condition | Level | Field Threshold † | Meaning |
|---|---|---|---|
slippery |
1 | friction < 70 |
SLIPPERY |
slippery |
2 | + surface_temp < 0 |
VERY SLIPPERY |
slippery |
3 | + friction < 60 |
ICE DETECTED |
windy |
1 | wind_gust > 64 |
WIND GUSTS |
windy |
2 | + wind_gust > 96 |
HIGH WINDS |
visibility |
1 | visibility < 1609 |
REDUCED VISIBILITY |
visibility |
2 | + visibility < 402 |
LOW VISIBILITY |
flooding |
1 | precip > 6 |
FLOODING POSSIBLE |
flooding |
2 | + precip > 8 |
FLASH FLOODING |
† Thresholds configurable with system attributes
Weather Fields
There are five weather data fields used for condition calculations:
friction: pavement friction coefficient in percentsurface_temp: temperature in degrees celciuswind_gust: gusting wind speed in kilometers per hour (kph)visibility: distance in meters (m)precip: one hour precipitation accumulation (mm)
System Attributes
These system attributes can be used to adjust thresholds for RWIS conditions.
| Attribute Name | Field | Default Threshold |
|---|---|---|
rwis_slippery_1_percent |
friction |
70 |
rwis_slippery_2_degrees |
surface_temp |
0 |
rwis_slippery_3_percent |
friction |
60 |
rwis_windy_1_kph |
wind_gust |
64 |
rwis_windy_2_kph |
wind_gust |
96 |
rwis_visibility_1_m |
visibility |
1609 |
rwis_visibility_2_m |
visibility |
402 |
rwis_flooding_1_mm |
precip |
6 |
rwis_flooding_2_mm |
precip |
8 |
Also, the rwis_obs_age_limit_secs determines the maximum valid age for a
weather sensor observation.
DMS Weather Sensors
An RWIS action tag can use data from one or more weather sensors. Each DMS can have its own set of sensors configured. A sign with no associated weather sensors will not activate messages from RWIS action tags.
Testing Condition Levels
The weather sensor properties form has buttons to test RWIS message automation. If the "Level 1" button is pressed, then all RWIS conditions from that weather sensor will report level 1 conditions. Similarly, the "Level 2" button causes each condition to report level 2. The testing mode will clear automatically the next time the sensor records an observation.