What are the tunnel restrictions concerning dangerous goods?

The correct answer involves the requirement that dangerous goods must not be packaged for an aircraft specifically when considering their transport through tunnels. This is crucial because transporting dangerous goods through confined spaces like tunnels significantly raises safety and hazard concerns. Such goods can pose serious risks if there is an incident in a tunnel, where ventilation and emergency access may be limited.

When dangerous goods are transported, they typically need to be handled in specific ways that align with safety regulations. The aspect of not being packaged for an aircraft refers to ensuring that these goods are not in a state that makes them suitable for air travel, where they would be subject to more stringent regulations. This means that their packing must reflect the conditions appropriate for land transport rather than air transport, considering the different risks involved in these modes of transportation.

The other options address important aspects of handling dangerous goods but do not directly pertain to the specific context of tunnel restrictions. Packaging requirements, labeling, and having a safety data sheet are all essential components of dangerous goods handling, but the crucial characteristic of tunnel transport regarding dangerous goods lies in their suitability and packaging requirements for various transport modes, particularly indicating that they should not be packaged as they would be for air transport.