The provisions of this chapter shall be held to be the minimum requirements for the promotion of the public safety, health, convenience, comfort, prosperity, and general welfare. These sections are not intended to interfere with, abrogate, annul or repeal any ordinance, rule or regulation which has been previously adopted, and is not in conflict with any of the provisions of this chapter. (§ 8 of proposition R, passed by voters 11-7-1978)