The roadway's reflective characteristics are defined by its physical surface properties. Sufficient data has been collected on the reflectance characteristics of different pavement types to allow them to be described by reflectance tables or R-Tables.
The R-Table types described below are from several global roadway standards.
|
R-Table |
Weighted Average Luminance Coefficient (Q0) |
Description |
|---|---|---|
| C1 | 0.10 | Concrete, CIE C1 |
| C2 | 0.07 | Asphalt, CIE C2 |
| N1 | 0.10 | CIE CLASS = 1 - very diffuse |
| N2 | 0.07 | CIE CLASS = 2 - concrete |
| N3 | 0.07 | CIE CLASS = 3 - asphalt |
| N4 | 0.08 | CIE CLASS = 4 - glossy asphalt |
|
NZN4 |
0.09 |
Diffuse chip seal surface |
|
NZR2 |
0.09 |
Glossy polished asphaltic surface |
|
R1 |
0.10 |
Mostly diffuse reflectance properties characteristic of Portland cement or asphalt surface with a minimum of 15% of the aggregates composed of artificial brightener aggregates. |
|
R2 |
0.07 |
A combination of diffuse and specular reflectances characteristic of asphalt surfaces with aggregate composed of a minimum of 60% gravel of size greater than 10mm. Also asphalt surfaces composed of 10-15% artificial brightener in aggregate mix. |
|
R3 |
0.07 |
Slightly specular reflectance typical of asphalt surfaces with dark aggregates, rough texture and some months of use. This surface is common in the United States. |
|
R4 |
0.08 |
Mostly specular surface typical of very smooth asphalt texture. |
| UKR2 | 0.05 | Porous Asphalt (UK) |
| W1 | 0.11 | Wet surface |
| W2 | 0.15 | Wet surface |
| W3 | 0.20 | Wet surface |
| W4 | 0.25 | Wet surface |
| ZOAB | 0.10 | CIE Class 2 Dutch Porous |