§ 348. Payment of cost of state thruways. The state shall construct or improve and maintain, at its own cost and expense, or with federal aid, state thruways, and shall acquire at its own cost and expense, or with federal aid or by gift, the rights of way necessary for such thruways. Such cost to the state shall, except for the preparation of plans and specifications and for engineering and other services incidental to the preparation of plans and specifications including field surveys and sub-surface investigations, be paid only from moneys specifically appropriated for such purpose, subject to the provisions of this chapter relating to federal aid; provided, however, that where any state highway or part thereof specified in section three hundred forty-one of this chapter or any improvement or reconstruction thereof shall be utilized by the commissioner of transportation as a part of any state thruway, moneys appropriated for the construction and reconstruction of state highways may be expended therefor and rights of way therefor shall be acquired as provided in article three of this chapter.