Final answer:
Buses must not carry more than a certain weight of any one class of allowed hazardous material to ensure safety.
Step-by-step explanation:
The subject of this question is Transportation and it is suitable for High School level students.
Buses must not carry more than a certain weight of any one class of allowed hazardous material to ensure safety. This weight limit is determined by the United States Department of Transportation hazardous materials regulations.
For example, if the weight of a single class of allowed hazardous material exceeds the weight limit set by the regulations, the bus would be violating the safety regulations.