(a) All exempt and nonexempt signs shall conform to the standards in the following sections, except as otherwise provided herein.
(b) Exempt and nonexempt signs shall conform to applicable standards in Tables 27 and 28, Sections 1153.18 to 1153.19.
(c) Required sign standards provided in Table 28, Section 1153.19 may be modified as provided in Table 29, Section 1153.20 provided the conditions specified therein are established and maintained at all times while the sign is established.