The Surface Transportation Board (Board) is amending 49 CFR part 1135 to add a rule that requires the Association of American Railroads (AAR) to annually update each Class I railroad's weighted average State tax rate for use in the Revenue Shortfall Allocation Method (RSAM). RSAM is one of three benchmarks that together are used to determine the reasonableness of a challenged rate under the Board's Simplified Standards for Rail Rate Cases, STB Docket No. 646 (Sub-No. 1) (STB served Sept. 5, 2007) (Simplified Standards).\1\ The new rule requires that the AAR submit this information by May 30 of each year. ---------------------------------------------------------------------------