Development sites shall have triangular vision clearance areas on all street corners to provide for unobstructed vision consistent with American Association of State Highway and Transportation Officials (AASHTO) standards. (See Figure 9.0500 Vision Clearance Area). Vision clearance areas shall be kept free of all visual obstructions from 2 ½ feet to 9 feet above the curb line. Where curbs are absent, the crown of adjacent streets shall be used as the reference point. These vision clearance requirements may be adjusted if consistent with the criteria of EC 9.8030(11) of this land use code.