It shall be unlawful for any person to ride on horseback on any street, alley, or highway, or over any bridge other than those on bridle paths in the parks, within the City limits, at a gait other than a walk. Provided, however, that the provisions of this section shall not apply to police or military officers or employees when engaged in the performance of their duties. City Code, 1976/83, art. 31, §78