Question Placards showing the type of hazardous materials in a vehicle are usually shaped like what? Answers An octagon A circle A diamond Explanation Hazardous materials warning placards are diamond-shaped. Take a FREE Practice Test Now This questions appears in the following tests: Arizona HazMat , Ohio HazMat , Oklahoma HazMat , South Carolina HazMat , Tennessee HazMat , Virginia HazMat , Wyoming HazMat , Hawaii Tank ,