Which characteristic is critical for placarding bulk shipments?

The critical characteristic for placarding bulk shipments is that Table 2 commodities require a minimum weight of 1001 pounds for proper placarding. This is essential because placarding is a safety measure that informs emergency responders and the public about the types of hazardous materials being transported. When the weight of a hazardous material reaches this threshold, the risks associated with those materials demand clear identification through placarding.

Each hazardous material class has specific requirements regarding when placards must be displayed, and reaching this weight ensures adequate precautions are taken. This helps to facilitate safe handling and response in emergencies. When hazardous materials are transported in quantities below the threshold, placarding may not be necessary, as the potential danger is deemed lower.

The other options do not meet the criteria necessary for determining placarding requirements as clearly as the correct answer does. For example, focusing solely on flammables ignores the broader range of hazardous materials that might require placarding based on their weight and classification. Classifying by shipping destination does not reflect the inherent hazards of the materials and their appropriate handling, while using specialized vehicles only addresses the method of transportation rather than the regulatory requirements governing the placarding itself.