A. Whenever the city traffic engineer determines that an emergency traffic congestion is likely to result from the holding of public or private assemblages, gatherings, or functions, or for other reasons, the city traffic engineer shall have power and authority to order temporary signs to be erected or posted indicating that the operation, parking or standing of vehicles is prohibited on such streets and alleys as the city traffic engineer shall direct during the time such temporary signs are in place. Such signs shall remain in place only during the existence of such emergency and the city traffic engineer shall cause such signs to be removed promptly thereafter.