Within a triangle formed by the street front and side lot lines and a line connecting these lot lines at points measured along these lot lines a distance of twenty-five (25) feet from their intersection, all fixtures, walls, fences, construction, hedges, shrubbery and other planting shall be limited to a height not over three (3) feet above the elevation of the street line level at the same intersecting streets except a reasonable number of trees pruned high enough to permit unobstructed vision to vehicular traffic. Within the said triangle, and in cases where front yards are terraced, the ground elevation of such front yards shall not exceed three (3) feet above the established street line elevation at the said intersecting streets.