Safety-sensitive function means any of the following duties, when performed by employees of recipients, subrecipients, operators, or contractors:
(1) Operating a revenue service vehicle, including when not in revenue service;
(2) Operating a nonrevenue service vehicle, when required to be operated by a holder of a Commercial Driver's License;
(3) Controlling dispatch or movement of a revenue service vehicle;
(4) Maintaining (including repairs, overhaul and rebuilding) a revenue service vehicle or equipment used in revenue service. This section does not apply to the following: an employer who receives funding under 49 U.S.C. 5307 or 5309, is in an area less than 200,000 in population, and contracts out such services; or an employer who receives funding under 49 U.S.C. 5311 and contracts out such services;
(5) Carrying a firearm for security purposes.
49 CFR § 655.4
For this part, the terms listed in this section have the following definitions. The definitions of additional terms used in this part but not listed in this section can be found in 49 CFR Part 40.