&quot; Coefficient of retro-reflection (symbol R &apos; ) &quot; means the quotient of the coefficient of luminous intensity R of a plane retro-reflecting surface and its area A
2.4.1 Coefficient de rétroréflexion (symbole R &apos; ) : quotient du coefficient d &apos; intensité lumineuse R de la surface rétroréfléchissante par sa surface A