The city council may, by resolution, establish increased speed limits when, pursuant to the provisions of Section 22357 of the California Vehicle Code, it is determined that on certain roadways speeds greater than twenty-five (25) miles per hour would facilitate the orderly movement of vehicular traffic and would be reasonable and safe on said roadways at the prima facie speed limits of thirty (30), thirty-five (35), forty (40), forty-five (45), and fifty (50) miles per hour respectively, and that on all remaining residential and business district roadways within the city, as set forth within Section 22352 of the California Vehicle Code, a vehicular speed of greater than the prima facie speed limit as to said roadways should not be increased. The limits shall be effective when appropriate signs giving notice thereof have been erected. (Prior code § 3002.2)