The City Council by resolution, pursuant to provisions of the California Vehicle Code and on the basis of engineering and traffic investigations, shall determine on which streets or portions thereof the speed permitted by State law is greater or less than is reasonable or safe under the conditions found to exist upon the described portions of such streets, and it is hereby declared that the prima facia speed limit on those streets or portions thereof shall be as set forth by said resolution of the City Council, as amended from time to time. (Ord. 977, 6-13-90)