Hazardous materials, or HAZMAT, are substances or materials that can burn, explode, react violently, or cause injury or harm to people, property, or the environment when transported in commerce. The DOT is responsible for developing, issuing, and enforcing the hazardous material regulations (HMR). These regulations govern the transportation of hazardous materials in interstate, intrastate, and foreign commerce. DOT’s primary safety goal is to reduce the risks posed by the transportation of hazardous materials.