Question When transporting hazardous materials, placards: Answers Should only be used with explosives. Should be used on all four sides of a vehicle. Should only be used by Class A licensed drivers. Should be used to reduce insurance rates. Explanation Hazardous materials warning placards must be used on all four sides of a vehicle transporting hazardous materials. Take a FREE Practice Test Now This questions appears in the following tests: New Jersey HazMat ,