Okla. Stat. tit. 47, § 47-11-307: No-passing zones

(a) The Oklahoma Department of Highways or other designated

authorities are hereby authorized to determine those portions of any

highway where overtaking and passing or driving to the left of the

roadway would be especially hazardous and may by appropriate signs

or markings on the roadway indicate the beginning and end of such

zones and when such signs or markings are in place and clearly

visible to an ordinarily observant person every driver of a vehicle

shall obey the directions thereof.

(b) Where signs or markings are in place to define a no-passing

zone as set forth in paragraph (a) no driver shall at any time drive

to the left side of the roadway within such no-passing zone or on

the left side of any pavement striping designed to mark such no-

passing zone throughout its length.