Whenever public safety or the improvement or repair of any street, alley or public place requires it, the Mayor may order any street, alley, or public place temporarily closed to traffic and the placing of signs indicating that the street, alley or public place is closed by order of the Mayor. Whenever such signs are so placed, no person shall ride or drive upon or cross such street, alley or public place, or in any manner, destroy, deface, or remove any such sign.