All materials, supplies and equipment required for the state road program and system shall be purchased and acquired by the commissioner through the department of purchases, except as otherwise provided by law. The director of purchases shall adopt rules and regulations governing and controlling acquisitions and purchases in accordance with accepted business practices so that no persons shall be precluded from participating and making sales thereof to the commission; shall establish and prescribe specifications, in all proper cases, for materials, supplies and equipment to be purchased; shall adopt and prescribe such purchase order, requisition or other forms as may be required; shall negotiate for and make purchases and acquisitions in such quantities, at such times and under contract, in the open market or through other accepted business methods and practices, as may be practicable in accordance with general law; shall determine whether to advertise for bids, to purchase by means of sealed bids and competitive bidding or to effect advantageous purchases through other accepted methods and practices; and shall post in a public place in the offices of the commission and the department of purchases, available to the public during all business hours, notices of all acquisitions and purchases to be made, at least two weeks prior to making such purchases.

All purchases and acquisitions shall be made in consideration and within limits of available appropriations and funds and in accordance with applicable provisions of article two, chapter five-a of this code, relating to expenditure schedules and quarterly allotments of funds.

The director of purchases shall make available the facilities and services of his department to the commissioner in the purchase and acquisition of materials, supplies and equipment and shall cooperate with the commissioner in all such purchases and acquisitions upon request of the commissioner. The actual expenses incurred by the director of purchases in all such cases shall be paid by the commissioner.