The in-depth security training under § 172.704(a)(5) is required only for hazmat employees who handle or perform regulated functions related to the transportation of the materials listed in § 172.800(b) or who are responsible for implementing the security plan. These hazmat employees must receive in-depth training on the specific portions of the plan for which they are responsible, including specific security procedures, employee responsibilities, and actions to be taken in the event of a security breach.