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 indications for road weather conditions can be activated using
device actions. An [rwis_ … ] condition 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 |
| Attribute Name | Description |
|---|---|
rwis_auto_max_dist_miles |
Maximum distance to auto-associate device |
rwis_obs_age_limit_secs |
Maximum valid age for an 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 use the nearest weather sensor, as long as it is not further than
rwis_auto_max_dist_miles away.
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.