HazMat Segregation Matrix & Placard Guide
Verify compatibility between dangerous goods classes and calculate statutory 4-sided trailer placard requirements.
STRICTLY FORBIDDEN: These materials MUST NOT be loaded, transported, or stored together in the same vehicle (49 CFR § 177.848).
DOT Placarding Mandatory
MANDATORY PLACARD: Aggregate Table 2 HazMat gross weight (2,050 lbs) meets or exceeds the 1,001 lbs DOT statutory threshold.
Understanding DOT 49 CFR § 177.848 Segregation Symbols
Federal hazardous materials transportation is strictly regulated under eCFR 49 CFR § 177.848 and enforced nationwide by the U.S. DOT PHMSA. Vehicles carrying mixed hazardous cargo must strictly observe compatibility symbols:
Materials MUST NOT be loaded, transported, or stored together in the same motor vehicle under any circumstances (e.g., Flammable Liquids with Oxidizers).
Materials must not be loaded adjacent to each other. Maintain at least 4 feet of horizontal clearance or use a full-height non-combustible partition.
No statutory segregation restriction applies. Cargo must still be properly blocked, braced, and protected from puncture or falling.
Frequently Asked Questions: DOT HazMat Transportation
What is the 1,001 lbs Placard Threshold Rule?
Under 49 CFR § 172.504(c), shipments containing only DOT Table 2 hazardous materials (such as Class 3 Flammable Liquids, Class 8 Corrosives, or Class 2.1 Flammable Gases) do not require motor vehicle placarding unless the aggregate gross weight of all HazMat reaches or exceeds 1,001 lbs (454 kg).
Which HazMat classes require placards at ANY quantity?
Materials in DOT Table 1 (§ 172.504(e)) require four-sided vehicle placards regardless of weight: Class 1.1/1.2/1.3 Explosives, Class 2.3 Poison Gas, Class 4.3 Dangerous When Wet, Class 5.2 Organic Peroxide (Type B temperature controlled), Class 6.1 (Inhalation Hazard Zone A/B), and Class 7 Radioactive (Yellow III).
Does Class 9 Miscellaneous Dangerous Goods require a placard?
No. Under 49 CFR § 172.504(f)(9), a vehicle transporting Class 9 materials (such as standalone lithium battery pallets UN3480) is not required to display Class 9 placards for domestic highway transportation within the United States.