In connection with the construction of any tollway project, an authority is authorized to construct grade separations at intersections of any tollway project with public highways and to change and adjust the lines and grades of public highways so as to accommodate the lines and grades to the design of the grade separation. The cost of the grade separations and any damages incurred in connecting and adjusting the lines and grades of public highways shall be ascertained and paid by the authority involved as part of the costs of the tollway project involved.