Okla. Stat. tit. 47, § 47-11-803: When local authorities may and shall alter maximum

limits.

A. Whenever local authorities in their respective jurisdictions

determine on the basis of an engineering and traffic investigation

that the maximum speed permitted under this article is greater or

less than is reasonable and safe under the conditions found to exist

upon a highway or part of a highway, the local authority may

determine and declare a reasonable and safe maximum limit thereon

which:

1. Decreases the limit at intersections;

2. Increases the limit within an urban district, but not to

more than sixty-five (65) miles per hour; or

3. Decreases the limit outside an urban district, but not to

less than thirty (30) miles per hour.

B. Local authorities in their respective jurisdictions shall

determine by an engineering and traffic investigation the proper

maximum speed for all arterial streets and shall declare a

reasonable and safe maximum limit thereon which may be greater or

less than the maximum speed permitted under Section 1-101 et seq. of

this title for an urban district.

C. Any altered limit established as hereinabove authorized

shall be effective at all times or during hours of darkness or at

other times as may be determined when appropriate signs giving

notice thereof are erected upon such street or highway.

D. As to streets and highways within the corporate limits which

are maintained by the Department of Transportation, local

authorities shall have joint authority with the Transportation

Commission to establish or alter speed limits; provided, however,

the speed limit on an interstate highway within such corporate

limits shall not be decreased to less than sixty (60) miles per

hour; and provided further, that no local authority shall impose

speed limits on any such street or highway substantially lower than

those justified by the highway design, capacity, and traffic volume

as determined by engineering studies.

E. Not more than six such alterations as hereinabove authorized

shall be made per mile along a street or highway except in the case

of reduced limits at intersections, and the difference between

adjacent limits shall not be more than ten (10) miles per hour.