[Radiance-general] Radiance and road design

[pillo]

Hi,
here pillo (me, superBEGINNER, may be spiderBEGINNER)
  with some questions about road design with Radiance:

i would like to use UNI's r-tables (UNI 10489),
where  r=[(luminance/illuminance)*cos3(g)],
to describe asphalt behavior.
i think BRDF is the way.
but i need some advices:

where i can found some examples of BRDF usage?
is it possible only with r tables ?

best regards,
pillo

PS r coefficients are measured at point P in function of the angle (g) 
between source rays (looking at P) and  surface normal, and the 
horizontal angle (b) between source rays and observation direction 
(looking at P).
The observation direction has a vertical, fixed, angle of 1�.
the source is tought punctual.