Any publicly owned vehicle or any vehicle operated by a corporation incorporated under Part 4 (commencing with Section 10400) of Division 2 of Title 1 of the Corporations Code for the purpose of the prevention of cruelty to animals, when used for removing dead animals, injured animals, or loose livestock, may, display flashing amber warning lights to the front or rear when necessarily parked on the roadway or when moving at a speed slower than the normal flow of traffic.