You will be reimbursed based on a constructive mileage rate limited to the cost that would be incurred for use of a Government-furnished automobile. This rate will be published in an FTR bulletin available at https://www.gsa.gov/ftrbulletins. If your agency determines the cost of providing a Government-furnished automobile would be higher because of unusual circumstances, it may allow reimbursement not to exceed the mileage rate for a privately owned automobile. In addition, you may be reimbursed other allowable expenses as provided in § 301-10.304.
41 C.F.R. §301-10.310