Final answer:
Freight carrying vehicles and passenger buses are typically required to carry a fire extinguisher, reflective triangles, and a reflective vest as warning equipment to ensure safety in the event of emergencies such as fires or breakdowns.
Step-by-step explanation:
The warning equipment that freight carrying vehicles and passenger buses must carry includes a fire extinguisher, reflective triangles, and a reflective vest. This is to ensure that in the event of an emergency, such as a fire or a breakdown, the vehicle can be made visible to other road users to prevent further incidents and the fire extinguisher can be used to tackle small fires before emergency services arrive. Safety protocols vary by location, but these pieces of equipment are commonly required by United States Department of Transportation regulations and are fundamental for maintaining safety on the roads.