To insure safe sight distances where streets intersect and where driveways intersect streets a minimum clear vision area shall be provided. On a corner lot in residential and/or business districts, there shall be no obstruction to vision by structures, grade or foliage other than power or utility poles between a height of three feet and a height of ten feet, measured above the average elevation of the existing surface of each street at the centerlines thereof.
(`94 Code, App. C, Art. VI, § 6)