authorized under titles 23 and 49, United States Code, and the provisions of the Fixing America's Surface Transportation Act shall not exceed total obligations of $44,234,212,000 for fiscal year 2018: Provided , That the Secretary may collect and spend fees, as authorized by title 23, United States Code, to cover the costs of services of expert firms, including counsel, in the field of municipal and project finance to assist in the underwriting and servicing of Federal credit instruments and all or a portion of the costs to the Federal Government of servicing such credit instruments: Provided further , That such fees are available until expended to pay for such costs: Provided further , That such amounts are in addition to administrative expenses that are also available for such purpose, and are not subject to any obligation limitation or the limitation on administrative expenses under section 608 of title 23, United States Code. (liquidation of contract authorization) (highway trust fund) For the payment of obligations incurred in carrying out Federal-aid highway and highway safety construction programs authorized under title 23, United States Code, $44,973,212,000 derived from the Highway Trust Fund (other than the Mass Transit Account), to remain available until expended. Administrative provisions—federal highway administration 120. (a) For fiscal year 2018, the Secretary of Transportation shall— (1) not distribute from the obligation limitation for Federal-aid highways— (A) amounts authorized for administrative expenses and programs by section 104(a) of title 23, United States Code