On or before January 1, of each year the state road commissioner shall ascertain and determine the total amount of available funds for expenditure in the whole state for the construction and reconstruction of state roads for the succeeding fiscal year, and shall also submit such determination of available funds together with the proposed expenditure thereof as a part of his budget request for such succeeding fiscal year. Of the amount so ascertained the commissioner may set aside as a "reserve fund" not to exceed twenty percent thereof, to be used and expended by him in his discretion in making desirable connections or economizing in construction.
All moneys received from the federal government for road construction shall be expended as provided, or as may hereafter be provided by act of Congress.
If at the end of any annual period, any money in the reserve fund remains unexpended or unappropriated, it shall be placed in the General Fund for reserve and distribution during the next annual period.
The remaining eighty percent, or, if such reserve fund is not set aside, then all the funds shall be appropriated in the following order and preference:
(1) For the construction, reconstruction, and maintenance of expressway and trunkline roads, and to comply with the requirements for the receipt of aid from the federal government;
(2) For the maintenance of all feeder and state local service roads, as provided in section six-a of this article;
(3) For the construction and reconstruction of feeder and state local service roads as prescribed in section six-a of this article.