(1) The driver of any vehicle shall obey the instructions of any traffic-control device placed or held in accordance with the provisions of this title, unless otherwise directed by a peace officer, subject to the exceptions granted the driver of an authorized emergency vehicle by this title.
(2) No provisions of this title for which traffic-control devices are required shall be enforced against an alleged violator if at the time and place of the alleged violation a 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 traffic-control devices are required, the section shall be effective even though no devices are erected and in place.
(3) Whenever traffic-control devices are placed or held in position approximately conforming to the requirements of this title, the devices shall be presumed to have been placed or held by the official act or direction of lawful authority, unless the contrary shall be established by competent evidence.
(4) Any traffic-control device placed or held pursuant to the provisions of this title and purporting to conform to the lawful requirement pertaining to those devices shall be presumed to comply with the requirements of this title, unless the contrary shall be established by competent evidence.