11 CFR 100.139: Unreimbursed payment for transportation and subsistence expenses.

(a) Transportation expenses. Any unreimbursed payment for transportation expenses incurred by any individual on behalf of any candidate or political committee of a political party is not an expenditure to the extent that:

(1) The aggregate value of the payments made by such individual on behalf of a candidate does not exceed $1,000 with respect to a single election; and

(2) On behalf of all political committees of each political party does not exceed $2,000 in a calendar year.

(b) Subsistence expenses. Any unreimbursed payment from a volunteer's personal funds for usual and normal subsistence expenses incident to volunteer activity is not an expenditure.