This recommendation about the transport of dangerous goods was made by the United Nations' committee of experts on the transport of dangerous goods and its objective is international harmonization of transportation requirements for securing the safe transportation of dangerous goods.
The recommendation itself is not legally binding, but various transport rules have been established based on this recommendation by international organizations and governments.
Targeted dangerous goods have a four-digit number (UN number), and transport, labeling, packaging methods, etc., are stipulated based on classification into nine classes according to the type of dangerous good, such as explosive, gas, or flammable liquid, when transporting.
*Nine classes (1: Explosives, 2: Gases, 3: Flammable liquids, 4: Flammable solids; substances liable to spontaneous combustion; substances which, on contact with water, emit flammable gases, 5: Oxidizing substances and organic peroxides, 6: Toxic and infectious substances, 7: Radioactive materials, 8: Corrosive substances, 9: Miscellaneous dangerous substances and articles)