(a) The department shall set and enforce speed limits on a road in a state park, wildlife management area, or other site under the control of the department as follows:
(1) 30 miles per hour on a park road or main drive;
(2) 20 miles per hour on a secondary road; or
(3) as posted by the department.
(b) The department shall:
(1) consult with the Texas Department of Transportation to determine if a speed limit under Subsection (a) is reasonable and safe based on an engineering and traffic control study; and
(2) amend the limit, if necessary.