Which Class of hazardous materials is restricted in loading amounts based on a transport index?

The correct answer is Class 7 (radioactive materials). Radioactive materials are subject to stringent regulations concerning their transport due to the potential health risks they pose to humans and the environment. The transport index is a key factor in determining how much radioactive material can be safely loaded during transportation.

The transport index is a numerical value assigned to a package containing radioactive material, which indicates the degree of radiation that can be expected at one meter from the package. This value helps ensure that exposure to radiation is minimized during transport. Therefore, the loading amounts for Class 7 materials are specifically restricted based on this transport index to maintain safety standards.

In contrast, the other classes of hazardous materials listed do not utilize a transport index for restrictions based on loading amounts in the same way that Class 7 does. For example, while flammable solids can have limitations, they do not specifically use a transport index to govern loading amounts like radioactive materials do. Each class of hazardous material has its own set of regulations, but the transport index is uniquely associated with Class 7.