Okla. Stat. tit. 47, § 47-12-202: Visibility distance and mounted height of lamps

A. Any requirement of this chapter as to distance from which

certain lamps and devices shall render objects visible, or within

which such lamps or devices shall be visible, shall apply during the

times stated in subsection B of Section 12-201 of this title in

respect to a vehicle without load when upon a straight, level,

unlighted highway, under normal atmospheric conditions unless a

different time or condition is expressly stated.

B. Any requirement of this chapter as to the mounted height of

lamps or devices shall mean from the center of such lamp or device

to the level ground upon which the vehicle stands when such vehicle

is without a load.