[Claim for Reimbursement of Car Rental Expenses]

An authorized certifying officer of the Department of Energy (DOE) requested a decision as to whether a DOE employee was entitled to reimbursement of car rental expenses which he incurred while on a temporary duty assignment. The mode of travel authorized at that time was common carrier and the authorization was for travel to and from the area air terminal. Otherwise, the vehicle was used for the personal convenience of the employee and not for official business. GAO found that reimbursement for the claimed expenses was allowable only in the amount of the constructive cost of round-trip transportation between the airport and the employee's lodgings at his temporary duty station. Accordingly, the voucher, if otherwise correct, may be submitted for payment.