The Federal Motor Carrier Safety Administration is proposing a new definition of a “tank vehicle” to clarify concerns about the impact of the definition on Commercial Drivers License requirements.

Under the proposal, which slightly revises earlier interpretations, a vehicle carrying multiple Intermediate Bulk Containers over 119 gallons each, amounting to 1,000 gallons or more, would be classified as a tanker, requiring a hazmat endorsement on the driver’s license.

The earlier interpretation, which raised concern among industry groups such as American Trucking Associations, was confusing because it implied that the hazmat endorsement was required to operate a tank larger than 119 gallons that is permanently attached to the trailer.

Comments on the proposed rule are due by November 25.