The City Manager, by and with the approval of the Mayor and the City Attorney, is hereby empowered to make regulations necessary to make effective the traffic ordinance of this city, and to make and enforce temporary or experimental regulations to cover emergencies or such conditions which are not directly covered by the Traffic Code and such emergency regulations which have the full force and effect of an ordinance experimental regulation to cover any such conditions; however, no such temporary or experimental regulation shall remain in effect for more than 90 days from the date it becomes effective.