It shall be unlawful to park or stand any motor vehicle, animal-drawn vehicle, bicycle, motorcycle or other form of conveyance in any of the zones designated as loading and unloading zones in this division, except a commercial vehicle, as defined by state statute, or a vehicle displaying a merchant/business loading or customer pick-up sign issued by the Greater Frederick Development Corporation for the purpose of loading and unloading merchandise, between the hours of 6:00 a.m. and 5:00 p.m. daily. No vehicle as hereinbefore permitted to park in a loading and unloading zone shall be parked in said zone for more than twenty (20) minutes. In the event that special circumstances make it desirable to provide special hours of use for certain loading and unloading zones, such special hours of use and particular purposes shall be set forth in the designation of such loading and unloading zone or zones in section 13-49, Designation, or shall be permitted by special exception granted by the police department. The section shall not apply on Sundays and legal holidays. (Code 1953, § 10.101; 1961 Supp., § 10.101; Ord. No. G-76-4, § 1, 3-4-76; Ord. No. G-90-53, § 1, 11-1-90; Ord. No. G-92-5, § 1, 3-5-92; Ord. No. G-94-4, § 1, 4-7-94)