A CMV carries an empty storage container tank with a rated capacity of 1,000 gallons temporarily attached to a flatbed trailer, and the container was not designed for transportation. Under the federal definition, how is it treated?

1. It is not considered a tank vehicle under the specific 49 CFR 383.5 exclusion
2. It is always a tank vehicle regardless of design
3. It always requires an X endorsement
4. It is a passenger vehicle