Attendance Requirements for Unloading Cargo Tanks
Pipeline and Hazardous Materials Safety Administration · Jun 26, 2001 · Reference No. 01-0132
Interprets: 49 CFR § 177.834(i), 49 CFR § 177.834(i)(2)
Reggie’s quick take
Someone asked whether the attendance rules in § 177.834(i)(2) apply when a cargo tank or tube trailer is unloaded after its motive power has been taken off the consignee's premises. PHMSA said no. Under that section, a cargo tank does not need an attendant when it has been placed on the consignee's premises and its motive power has been removed from both the tank and the premises. PHMSA also said a tube trailer is not a cargo tank under that section, so it does not need attendance during unloading.
Written by AI (Claude) on Oct 22, 2026. Robots make mistakes and leave things out, so the letter below is what counts. Not legal advice.
This is in response to your May 23, 2001 letter, regarding the attendance requirements for unloading tube trailers and cargo tanks under the Hazardous Materials Regulations (HMR- 49 CFR Parts 171-180). Specifically, you ask whether attendance requirements as specified in § 177.834(i)(2) apply when a cargo tank or tube trailer is unloaded and the motive power has been removed and taken off the consignee's premises.
The answer is no. Under § 177.834(i)(2), a cargo tank unloading operation need not be attended when the cargo tank has been placed on the consignee's premises and the motive power has been removed from the cargo tank and removed from the premises. Cylinders permanently mounted on a motor vehicle are commonly referred to as a "tube trailer." A tube trailer is not considered a cargo tank and therefore is not subject to, the provisions of § 177.834(i) and does not require attendance when being unloaded.
I hope this satisfies your request.
A letter of interpretation applies the regulations to the facts the requester described. It isn’t a regulation and isn’t legal advice. The agency’s copy.