When must hazardous materials be re-evaluated for transport?

The correct answer reflects the importance of ongoing assessments of hazardous materials to ensure safety during transport. Hazardous materials must be re-evaluated at least every three years or whenever new studies suggest that there have been changes in the characteristics or hazards associated with those materials. This approach ensures that any new information about potential risks, emerging technologies, or materials handling practices are taken into account, ultimately enhancing safety for both the public and the environment.

Regular re-evaluation is crucial because the properties of certain materials or their handling methods may change over time due to new research findings or advancements in safety technology. This periodic review helps to identify any increased risks or new safety measures that should be implemented, maintaining compliance with safety protocols.

The other options do not capture the necessary frequency and adaptability required for the safe transport of hazardous materials. Yearly reassessments might be excessive in some cases, while only evaluating materials when shipments fail to meet safety standards or when new laws are passed could lead to hazardous situations if issues arise beforehand. Regular, proactive evaluations are essential for minimizing risks associated with hazardous materials during transportation.