(A) The driver of any vehicle and the motorman of any streetcar shall obey the instructions of any official traffic-control device applicable thereto placed in accordance with the provisions of this chapter, unless otherwise directed by a traffic or police officer, subject to the exceptions granted the driver of an authorized emergency vehicle in this chapter.
(B) No provision of this chapter for which official traffic-control devices are required shall be enforced against an alleged violator if at the time and place of the alleged violation an official device is not in proper position and sufficiently legible to be seen by an ordinarily observant person. Whenever a particular section does not state that official traffic-control devices are required, such section shall be effective even though no devices are erected or in place.
Statutory reference:
Similar provisions, see Tex. Transportation Code § 544.004