(a) Nothing in this chapter is intended to conflict with any federal law, and in case of such conflict such portion as may be in conflict with such federal law is declared of no effect to the extent of the conflict.

(b) The department is authorized to take the necessary steps to secure the full benefit of any federal-aid program and to meet any contingencies not provided for in this chapter, abiding at all times by a fundamental purpose to plan, construct, reconstruct, and maintain, as economically as possible, the public roads and other major transportation facilities of Georgia which will best promote the interest, welfare, and progress of the citizens of Georgia.