What is the purpose of a UN number?

The UN number serves as a unique identifier for specific dangerous goods as defined by the United Nations. This number provides quick, standardized information about the item being transported, aiding in the proper handling and emergency response during transportation. For instance, if an emergency response team knows the UN number, they can immediately access crucial information regarding the potential hazards associated with the substance, which is vital for ensuring safety.

The other options do not accurately reflect the purpose of a UN number. Identifying the type of transport vehicle needed or determining the cost of shipping are not roles that the UN number plays. Similarly, while classification based on weight may be relevant in other contexts, the UN number primarily focuses on identifying the nature of the material and not its weight.