While away from their homes, regular places of business, or official stations in performance of services under this part, members of the Board of the Commission and the representatives of the United States on the Consultative Committee referred to in section 3615 of this title and on the Joint Commission on the Environment referred to in section 3616 of this title shall be allowed travel or transportation expenses, including per diem in lieu of subsistence, in the same manner as persons employed intermittently in Government service are allowed expenses under section 5703 of title 5.