Subject to the provisions of Chapter 4, Title 41, the State Department of Transportation is authorized to rent, construct, or purchase such buildings, stock, machinery, tools, materials, and other equipment as it may find necessary for use in carrying out the provisions of this chapter and pay for the same out of the State Highway Fund. It shall also, subject to the provisions of Chapter 4 of Title 41, pay out of said fund the necessary expenses of the department of every description, including traveling expenses of the officials and engineers, superintendents, foremen and clerks, etc., while in the actual performance of their duties authorized or imposed by this chapter and also the cost of all supplies or materials furnished for said department and for the maintenance of all machinery used by the department or its agent.