Except as provided in Title 6, Chapter 4 of this code, and as otherwise hereinafter provided, it shall be unlawful to obstruct City streets, including sidewalk areas of streets, by the parking of vehicles or by placing therein any materials in order to store the same, or for any purpose not incidental to the transportation thereof. Sidewalk areas within the intent and meaning of this chapter are strips of land forming parts of City streets as established by official plats and records, being six feet in width as measured from lot lines of lands abutting on streets toward the centerline of streets. Main Street is excepted from the foregoing definitions. (1985 Code, § 12.06.010)