The X endorsement provides an endorsement that covers both tanker vehicles and hazardous materials. Combining these two into one endorsement is a logical option, given that tankers are often used to haul hazardous materials.

Before a driver can haul a tanker carrying hazardous materials, the driver must pass both the tanker and hazardous materials knowledge tests. The material included in the comprehensive online practice test covers all information that will be needed to pass these two tests and to receive the X endorsement.