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17 Graphical illustration of the measuring principles
17.1 Night visibility R
L
R
L
is the coefficient of retroreflected luminance (night visibility) of road markings.
The observation angle of 2.29° corresponds to the viewing distance of a vehicle
driver of 32 m from height of 1.20 m.
The illumination angle of 1.24° corresponds to the illumination distance of a head
lamp of 30 m from height of 0.65 m.
Above mentioned angle definitions are related to EN 1436.
ASTM E1710 uses the same geometry just with different description of the angles.