At every street corner where streets intersect and where the curb lines of any two streets in the city form a corner, all trees, shrubbery, hedge and other live fences and all other plants and vegetation shall be kept cut and trimmed and all other obstructions removed so as to permit at all times a clear view from the street to street across each such corner from a height of three feet to a height of seven feet above the center of the street at such corner, and such clear view shall be kept open and maintained at all times over a triangular space formed by the curb line of each of such streets and a straight line connecting points on such curb lines twenty-five feet back each way from such corner. (Prior code § 15-9)