adjustment that would have applied under clause (i) if item (aa) were not in effect, and (cc) an adjustment of rates under item (bb) remains subject to item (aa). (II) If an adjustment of rates under clause (i) for a calendar year would result in rates in subparagraphs (A)(i), (A)(iii), and (D) in effect for the calendar year less than the rates in effect under such subparagraphs for the preceding calendar year— (aa) no adjustment of such rates shall be made for the calendar year, and (bb) the rates in subparagraphs (A)(i), (A)(iii), and (D) for the calendar year shall be the rates in effect under such subparagraphs for the preceding calendar year. (iv) Double indexation For purposes of clause (i), the double indexation for any calendar year is the sum of— (I) the highway construction cost adjustment, and (II) the CAFE fuel saved adjustment. (v) Highway construction cost adjustment For purposes of clause (iv), the highway construction cost adjustment for any calendar year is the percentage (if any) by which— (I) the National Highway Construction Cost Index for the preceding calendar year, exceeds (II) the National Highway Construction Cost Index for calendar year 2016 or, if applicable, the first year of a successor index. (vi) National Highway Construction Cost Index for any calendar year For purposes of clause (v), the National Highway Construction Cost Index for any calendar year is the average of the National Highway Construction Cost Index as of the close of the 12-month period ending on June 30 of such calendar year. (vii) National Highway Construction Cost Index For purposes of clause (v), the term National Highway Construction Cost Index means the last National Highway Construction Cost Index published by the Department of Transportation or successor index. (viii) CAFE fuel saved adjustment For purposes of clause (iv), the CAFE fuel saved adjustment for a calendar year is the percentage (if any) by which annual motor fuel use is reduced by the estimated CAFE fuel saved for that calendar year from the