Every sign erected pursuant to this chapter shall be of hexagonal design and in conformance with the National Safety Council Standards and shall bear the word “STOP” in letters not less than eight inches in height and such sign shall at nighttime be rendered luminous by efficient reflecting elements on the face of the sign. Every stop sign shall be located as near as practicable at the nearest line of the crosswalk on the near side of the intersection, or, if none, at the nearest line of the roadway and shall be placed on the right side of such street.