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The Place of the Road Surface Condition Detection System
Field Operational Test Facilities
Field Operational Test Issues and Evaluation Methods
Issues
Detection characteristics of the various sensors (laser radar, electric wave radiometer, visible image sensors, and optical fiber sensors) in the field are evaluated under the following three headings:
- Road surface condition detection performance on actual road surfaces
- Road surface detection performance under changing meteorological conditions, traffic environment, natural environment, road environment, etc. (road surface condition determination accuracy, detection rate, detection time, detection range, certainty determination function, self-diagnostic function)
- Reliability and durability in the test environment Collected data
Determination of Road Surface Conditions
- Basic:
- Document determination standards and make visual determination of road surface conditions
- Subsidiary:
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- Meteorological quantities
(Weather, atmospheric temperature, precipitation, road temperature, insolation, wind direction & speed, visibility)
- Records of snow and ice work (snow removal, chemical agent application)
- Traffic volume (traffic counter data)
- Physical quantities of snow and ice
(Physical quantities: Density, water content, frictional coefficient, hardness, conductivity)
- Substitute monitoring camera image for on-site visual inspection and collect long-term data
| Use views of local people as reference for visual determination |
Reference: Visual Determination Standards
| 5 categories |
9 categories |
Features of visual determination |
|---|
| Dry |
Dry |
Absolutely no water. Diffuse reflective surface with low brightness and even distribution of light |
| Wet |
Wet |
The surface is moist, forming mirror-like areas, and seems bright overall. Vehicle tires leave tracks. |
| Water film |
Shallow water film |
A layer of water forms on the surface and reflects the background. Puddles form where the road surface is indented. |
| Thick water film |
Same as above, with film thickness 1 mm or more |
| Snow cover |
New snow |
The road surface is covered with fallen snow or snow blowing along the ground, and appears white. There are no tire tread marks on the road. Possible even where there are ruts. |
| Slush |
It appears white due to the snow, it is splashed up by cruising vehicles, and it often turns brown. |
| Compacted snow |
It appears white due to the snow, and it is not splashed up by cruising vehicles. |
| Freezing |
Compacted snow
with ice crust |
It appears white due to the snow, and the road surface frozen after snow removal makes a rattling sound. It is glossy. |
| Ice film |
This is ice with a slippery surface and is highly glossy. |
Road Surface Conditions and Detection Accuracy
Road surface conditions
and accuracy |
Frictional coefficient |
Remarks |
|---|
| 5 conditions |
9 conditions |
 |
|---|
| Dry |
Dry |
 |
Dry conditions other than the below |
| Wet |
Wet |
 |
Moist condition |
| Water film |
Shallow water film |
 |
Water film thickness of 0-1 mm (highly dependent on speed) |
| Thick water film |
 |
Water film thickness of 1 mm or more (highly dependent on speed) |
| Snow cover |
Slush |
 |
Sticky snow, crusty snow, granular snow |
| New snow |
 |
New snow, ordinary snow cover |
| Compacted snow |
 |
Hard-packed snow, compacted snow |
| Freezing |
Compacted snow
with ice crust |
 |
Compacted snow with slippery surface, ice with rough surface |
| Ice film |
|
Black ice, ice with slippery surface |
- Note:
- The frictional coefficient varies complexly depending on tire type and other vehicle specifications.
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Snow cover and freezing are according to Niigata Experimental Laboratory, Public Works Research Institute, materials on measurement by frictional coefficient measurement vehicle.
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