The Department of Transportation shall annually prepare and file with the Board of Public Roads Classifications and Standards a plan for specific highway improvements for the current year. The annual plan shall be filed on or before July 1 of each year. In so doing, the department shall take into account all federal funds which will be available to the department for such year. The board shall review each such annual plan to determine whether it is consistent with the department's current six-year plan. The department shall be required to justify any inconsistency with the six-year plan to the satisfaction of the board.