There are several situations when vehicles must display hazardous material identification numbers.
When a transport vehicle or freight container contains a single hazardous material in non-bulk packages, 49 CFR 172.301(a)(3) requires that the identification number be displayed on each side and each end of the vehicle or freight container when all of the following apply to the shipment:
- Each package within the transport vehicle or freight container is marked with the same proper shipping name and identification number
- The aggregate gross weight of the hazardous material is 8,820 lb or more
- All the hazardous material is loaded at the same facility
- Transport vehicle or freight container contains no other material, hazardous or otherwise
- This requirement does not apply to Class 1, Class 7, or non-bulk packages that do not require the identification number marking
49 CFR 172.313(c) requires that the transport vehicle or freight containers bearing poison inhalation hazards be marked on each side and each end with the identification number of the hazardous material when all of the following apply to the shipment:
- Material is in Hazard Zone A or B
- Each package is marked with the same proper shipping name and identification number
- Transport vehicle or freight container is loaded at one facility with 2,205 lb or more aggregate gross weight
If the transport vehicle or freight container contains more than one material classified as poisonous by inhalation, it must be marked with the identification number for one material, determined as follows:
- For different materials in the same hazard zone, with the identification number of the material having the greatest aggregate gross weight; and
- For different materials in both Hazard Zones A and B, with the identification number for the Hazard Zone A material
49 CFR 172.302(a) requires bulk packages with a capacity of 1,000 gallons or more to be marked with the hazardous material identification number on each side and each end and on two opposite sides if the capacity is below 1,000 gallons. For cylinders permanently installed on a tube trailer motor vehicle, the identification number must be marked on each side and each end of the motor vehicle.
When portable tanks, cargo tanks, and other bulk packaging are loaded in or on a transport vehicle or freight container and their identification number markings are not visible, 49 CFR 172.326(c), 49 CFR 172.328(a)(3), and 49 CFR 172.331(c) require the transport vehicle or freight container to be marked as required by 49 CFR 172.332 on each side and each end with the identification number of the hazardous material.
49 CFR 172.330(a) requires that tank cars containing hazardous material be marked on each side and each end with the identification number. 49 CFR 172.330(b) requires that motor vehicles or rail cars used to transport a multi-unit tank car tank of hazardous material be marked on each side and each end with the identification number.
49 CFR 172.332 authorizes the identification number to be displayed on orange panels, within a required placard, or in a white, square-on-point configuration. These identification number requirements are in addition to the applicable placarding requirements for the shipment. See 49 CFR 172.504 for general placarding requirements.
