What do the hazardous material transport rules regulate?

The hazardous material transport rules specifically regulate the transport of dangerous substances, which are materials that pose risks to health, safety, property, or the environment during their movement. These regulations ensure that such materials are properly labeled, packaged, and handled to prevent accidents and ensure safe delivery. This includes substances like chemicals, explosives, and radioactive materials.

In contrast, the other choices do not pertain to hazardous material transport. The movement of personal belongings does not involve the same level of risk or regulation. Public transportation safety focuses on the safe transport of passengers and does not specifically address hazardous materials. Lastly, the collection of roadside litter is concerned with environmental cleanliness rather than the safety protocols for transporting dangerous substances. Thus, the focus of the question aligns directly with the second option.