Spacing of signs

1. Signs adjacent to the federal-aid primary system may not be located in a manner as to obscure or otherwise physically interfere with the effectiveness of an official traffic sign, signal, or device or obstruct or physically interfere with the driver's view of approaching, merging, or intersecting traffic. 2. On interstate highways and expressways on the federal-aid primary system: a. Two signs may not be placed less than five hundred feet [152.4 meters] apart. b. In areas outside of incorporated cities, signs may not be located adjacent to or within five hundred feet [152.4 meters] of an interchange, intersection at grade, or safety rest area. The five hundred feet [152.4 meters] must be measured along the interstate or freeway from the beginning or ending of pavement widening at the ramp exit from or entrance to the main-traveled way. 3. On highways, other than interstate or expressways, on the federal aid primary system: a. Outside of incorporated cities, two signs may not be placed less than three hundred feet [91.44 meters] apart. b. Inside incorporated cities, no two signs shall be spaced less than one hundred feet [30.48 meters] apart. 4. The spacing between sign provisions of this section do not apply to signs separated by buildings or other obstructions in a manner that only one sign facing located within the above spacing distances is visible from the highway at any one time.