A change in the official definition of a "tank vehicle" has led to confusion about who needs a tank truck endorsement on a commercial driver's license.

The Federal Motor Carrier Safety Administration made the change last year in a rule that tightened its standards for commercial driver's license testing, and created new commercial learner's permit.

The agency defined a tank vehicle as one designed to transport any liquid or gaseous material in tanks that are either permanently or temporarily attached to the chassis and are rated at more than 119 gallons and aggregated to 1,000 gallons or more. A flatbed carrying empty tanks rated at 1,000 gallons or more is not considered a tank carrier.

According to the National Tank Truck Carriers, this means that if a driver is hauling a load with aggregate bulk packages over 119 gallons totaling 1,000 gallons or more, he must have a tank truck endorsement.

NTTC went on to say that this change led to questions about whether a driver of a flatbed or a van hauling Intermediate Bulk Containers totaling more than 1,000 gallons would need an endorsement. The trade association put the question to FMCSA and got this response:

"We do consider that an IBC that is strapped, chained, or otherwise secured to a vehicle in compliance with our cargo securement rules is considered to be temporarily attached to the vehicle. So, if the aggregate capacity of the IBCs on a truck is greater than 1,000 gallons it would meet our definition of a tank vehicle and the driver would be required to have the tank endorsement."

States have until July 2014 to adopt the new definition. According to a bulletin from the South Carolina Trucking Association, some states already have made the change and are enforcing the new definition. One such state is Louisiana, which has begun citing drivers but will not levy any fines until March.