An X endorsement is a type of endorsement added to a commercial driver’s license (CDL) that allows a driver to operate a combination of vehicles that includes a tank vehicle along with hazardous materials. The “X” endorsement is required for drivers who operate a commercial motor vehicle that is designed to transport any hazardous liquid or gaseous materials within a tank or tanks having an individual rated capacity of more than 119 gallons and an aggregate rated capacity of 1,000 gallons or more that is either permanently or temporarily attached to the vehicle or the chassis.
