Sec. 3. A vehicle transporting explosives must meet one (1) of the following requirements:
(1) Be marked or placarded on each side and the rear with the word "explosives" in letters not less than eight (8) inches high.
(2) Have displayed on the rear of the vehicle a red flag not less than twenty-four (24) inches square marked with the word "danger" in white letters six (6) inches high.