Section 5(3)(c) in The National Highways fee (Determination of Rates and Collection) Rules, 2008
(c)WPI A means [the wholesale price index for the month of December of the immediately preceding year] [Substituted for the words "the wholesale price index of the week ending on or subsequent to 1st January" by Notification No. G.S.R. 950(E), dated 3.12.2010 (w.e.f. 5.12.2008)] immediately preceding the date of revision under these rules; and