If a vehicle contains 500 pounds each of explosives 1.1 and 1.3, which placards must be used?

The correct answer is that Explosives 1.1 placards must be used. In the context of transporting hazardous materials, particularly explosives, the classification determines which placards are necessary.

Explosives are categorized into different divisions based on their characteristics, and Division 1.1 represents more hazardous explosives that can create a mass explosion, while Division 1.3 pertains to explosives that can create a projection hazard but are less hazardous than 1.1. When determining placarding requirements, the more dangerous classification takes precedence.

In this case, since the vehicle is carrying 500 pounds of both Explosives 1.1 and 1.3, the requirement is to use the placard for the higher risk item, which is the Explosives 1.1 placard. This ensures that all safety measures are taken into account, and emergency responders are adequately informed about the potential hazards associated with the load.

Using only the Explosives 1.3 placard or any other alternative options would not comply with the regulations that prioritize the most dangerous materials, which is essential for safety during transport.