(a) The commissioners court of a county by resolution may request the Texas Transportation Commission to determine and declare a reasonable and safe prima facie speed limit that is lower than a speed limit established by § 545.352 on any part of a farm-to-market or a ranch-to-market road of the highway system that is located in that county and is without improved shoulders.
(b) The commission shall give consideration to local public opinion and may determine and declare a lower speed limit on any part of the road without an engineering and traffic investigation, but the commission must use sound and generally accepted traffic engineering practices in determining and declaring the lower speed limit.