The U.S. Department of Transportation (DOT) has a regulatory role in ensuring the safe transportation of hazardous materials within the United States. The DOT's Hazardous Materials Regulations (HMR) prescribe requirements for classifying, packaging, marking, labeling, handling, and transporting such materials.

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Here's a brief overview of items that are generally restricted or regulated by the DOT:

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1. Explosives: Materials that are designed to function by explosion or which, in their packaging, can result in a hazardous release.

2. Gases: This can include compressed gases, liquefied gases, dissolved gases, refrigerant gases, and aerosol sprays.

3. Flammable Liquids: Liquids that have a flash point (temperature at which they can ignite) below a certain temperature.

4. Flammable Solids: Items that can ignite easily and sustain combustion. This includes certain types of matches, and materials like magnesium.

5. Oxidizers & Organic Peroxides: Substances that can yield oxygen to stimulate the combustion of organic material.

6. Toxic (Poison) and Infectious Substances: Includes materials that are toxic by inhalation or which pose a biological risk.

7. Radioactive Materials: Any material containing radionuclides where both the activity concentration and the total activity exceed certain pre-defined values.

8. Corrosives: Substances that can cause severe damage to human skin or significantly corrode steel or aluminum.

9. Miscellaneous Hazardous Materials: This is a broad category and includes environmentally hazardous substances, elevated temperature materials, and any other materials that meet the definition for hazardous materials but don’t fit into other categories. Asbestos and dry ice are examples.

10. Lithium Batteries: Due to risks associated with fires, there are special regulations surrounding the transportation of lithium-ion and lithium metal batteries.

 

These are general categories, and within each, there are specific rules and exceptions. Some materials might be allowed for transport but under strict regulations regarding packaging, labeling, and documentation. Companies involved in the shipping and transportation of goods, especially logistics companies, must be well-versed in these regulations to ensure compliance and safety.