No vehicle, unless specifically authorized by some other section of this code or by posted signs, shall be driven at a speed greater than twenty five (25) miles per hour upon any street within this town. The board of trustees may determine that certain other speed regulations shall be applicable upon specified streets in certain areas, in which event it shall be unlawful for any person to drive a vehicle at a speed in excess of any speed so declared when signs are in place giving notice thereof. (1998 Code)