41 CFR § 301-10.164
When may I use extra-fare train service?
June 9, 2020
You may use extra-fare train service whenever your agency determines it is more advantageous to the Government or is required for security reasons. Extra-fare train service is considered to be a class above the lowest class offered on any particular train and must be authorized/approved as provided in §301-10.162.
[FTR Amdt. 2009-06, 74 FR 55149, Oct. 27, 2009]