(a) (1) In this section, “authority” means a regional tollway authority governed by Chapter 366.
(2) If an authority determines from the results of an engineering and traffic investigation that a prima facie speed limit described in this subchapter is unreasonable or unsafe on a part of a turnpike constructed and maintained by the authority, the authority by order recorded in its minutes shall determine and declare a reasonable and safe prima facie speed limit for vehicles or classes of vehicles on the turnpike.
(b) In determining whether a prima facie speed limit on a part of a turnpike constructed and maintained by the authority is reasonable or safe, the authority shall consider the width and condition of the pavement, the usual traffic on the turnpike, and other circumstances.

(c) A prima facie speed limit that is declared by the authority in accordance with this section is effective when the authority erects signs giving notice of the new limit. A new limit that is adopted for a turnpike project constructed and maintained by the authority in accordance with this section is effective at all times or at other times as determined.
(d) The authority’s power to alter prima facie speed limits is effective and exclusive on any part of a turnpike project constructed and maintained by the authority inside and outside the limits of a municipality, including a home-rule municipality.
(e) The authority may not:
(1) alter the general rule established by § 545.351(a); or
(2) establish a speed limit of more than 75 miles per hour.
(f) The authority, in conducting the engineering and traffic investigation specified by Subsection (a), shall follow the procedure for establishing speed zones adopted by the Texas Department of Transportation.