; (2) over-the-road bus drivers, security personnel, dispatchers, maintenance and maintenance support personnel, ticket agents, other terminal employees, and other employees of an over-the-road bus operator or terminal owner or operator that the Administrator determines should receive security training under this section or that is receiving security training under other law; or (3) security personnel, dispatchers, locomotive engineers, conductors, trainmen, other onboard employees, maintenance and maintenance support personnel, bridge tenders, and any other employees of railroad carriers that the Administrator determines should receive security training under this section or that is receiving security training under other law. 1977. Voluntary use of credentialing (a) In general An applicable individual who is subject to credentialing or a background investigation may satisfy that requirement by obtaining a valid transportation security card. (b) Issuance of cards The Secretary of Homeland Security— (1) shall expand the transportation security card program, consistent with section 70105 of title 46, United States Code, to allow an applicable individual who is subject to credentialing or a background investigation to apply for a transportation security card