Which hazardous materials require a Hazardous Materials Special Permit to transport?

A Hazardous Materials Special Permit is necessary for transporting hazardous materials that pose significant risks, particularly in large quantities or due to their inherent dangers.

The transportation of a highway route-controlled quantity of Class 7 materials, which includes certain radioactive materials, falls under strict regulations because of the potential radiation hazards these materials can pose to public safety and the environment. By requiring a special permit, regulations ensure that the transportation of such materials is managed under strict guidelines, minimizing risks associated with their handling.

Similarly, materials classified as "poisonous by inhalation" that meet specific criteria also necessitate a Hazardous Materials Special Permit due to the severe health risks they pose. These materials can be highly dangerous if they are released into the environment or inhaled, making it crucial to control their transportation under rigorous safety standards.

The inclusion of both scenarios under the requirement for a special permit helps ensure that vehicles transporting these materials are properly equipped, that drivers are adequately trained, and that routes are chosen to mitigate risk to the public. Thus, the need for a Hazardous Materials Special Permit applies to both types of materials mentioned, making that the correct answer.