A person shall not be convicted of violating a provision of the vehicle code for which an official traffic control device is required if the device is not in proper position and legible to a reasonably observant person at the time and place of the alleged violation.
Whenever a particular section of the vehicle code does not state that traffic control devices are required, the section is effective even though no devices are erected or in place.
When a traffic control device is placed in position approximately conforming to the requirements of the traffic regulations or other laws of this state, the device is presumed to have been placed by an official act or at the direction of lawful authority unless the contrary is established by competent evidence.
A traffic control device placed under the vehicle code or other laws or regulations of this state and purporting to conform to the lawful requirements pertaining to that device is presumed to comply with the requirements of the vehicle code unless the contrary is established by competent evidence. [1983 c.338 §167]