Okla. Stat. tit. 21, § 21-1753.4: Erection of signs and markers along state and federal

highways.

The State Highway Department is hereby authorized and directed

to cause to be erected upon the property of or rights-of-way of

state and Federal highways, at locations most appropriate for

carrying out the purposes and intent of this act, signs or markers

for each prohibited act enumerated herein, of a size not less than

thirty (30) inches square with plainly visible wording to inform

users of said highways that the acts enumerated herein do constitute

a crime and the maximum penalty for violations, and such additional

wording as the State Highway Department deems desirable to assist in

carrying out the purposes and intent of this act. Any sign or

marker so erected or placed shall be placed at a right angle to the

roadbed. The location of signs or markers upon the right-of-way

shall in no manner interfere with the signs or markers used to

designate route numbers or traffic control markers, signs, signals

or devices.