FMCSA and PHMSA Regulatory Framework for Tankers
Tanker operations are regulated by two primary federal agencies: the Federal Motor Carrier Safety Administration (FMCSA), which governs driver qualification, vehicle inspection, hours of service, and carrier safety; and the Pipeline and Hazardous Materials Safety Administration (PHMSA), which governs the transport of hazardous materials, tank construction standards, and hazmat incident reporting. Under 49 CFR Part 178, PHMSA specifies the construction specifications for cargo tanks (designated MC 306, MC 307, MC 312, MC 331, and DOT 406, 407, 412, 331, 412 specification codes). The MC designation (Motor Carrier) has been replaced by DOT designations for newer tanks, though many MC-specification tanks remain in service under grandfather provisions. Each specification governs the maximum allowable working pressure (MAWP), material of construction, valve requirements, and test intervals. For example, DOT 406/MC 306 tankers (petroleum delivery trucks) have a MAWP of 1 psig and are designed for flammable liquids. DOT 407/MC 307 tanks have a MAWP of 25 psig and are used for chemical commodities. DOT 331 tanks are designed for compressed gases at MAWP of 500 psig or more. All cargo tanks must display the specification placard on the manufacturer's data plate, which is typically located on the driver's side near the manhole or on the front head of the tank.