What does the "D" sign in symbols represent?

The "D" sign in symbols refers specifically to "Domestic restrictions." This designation indicates that certain limitations or regulations apply to the transportation of hazardous materials within the domestic sphere, emphasizing compliance with national laws and standards. When transporting hazardous materials, it's essential to understand these restrictions as they dictate packaging, labeling, and handling procedures that must be followed to ensure safety and legality during transit.

Understanding and recognizing this symbol allows transporters and shippers to adhere strictly to domestic regulations, which is critical in preventing accidents and ensuring public safety. Proper training and awareness of these designations help ensure that the transportation of hazardous materials is conducted safely and in compliance with applicable laws.