You will be reimbursed based on a constructive mileage rate limited to the cost that would be incurred for use of a Government automobile. This rate will be published in an FTR bulletin available at http://www.gsa.gov/ftr. If your agency determines the cost of providing a GOA would be higher because of unusual circumstances, it may allow reimbursement not to exceed the mileage rate for a POA. In addition, you may be reimbursed other allowable expenses as provided in § 301-10.304.
Code of Federal Regulations
[FTR Amdt. 2010-07, 75 FR 72967, Nov. 29, 2010]