41 CFR § 301-72.2
May we utilize methods of transportation other than common carrier (e.g., POVs, chartered vehicles, etc.)?
June 9, 2020
Yes, but only when use of common carrier transportation:
(a) Would interfere with the performance of official business;
(b) Would impose an undue hardship upon the traveler; or
(c) When the total cost by common carrier would exceed the cost of the other method of transportation.