U.S. freight railroads completed a record-breaking year by originating 1,267,054 carloads of freight in December 2006 and an additional 889,172 intermodal trailers and containers, the Association of American Railroads (AAR) reports. Full-year 2006 U.S. carloads totaled 17,380,102, up 1.2 percent (213,751 carloads) over 2005. Full-year 2006 U.S. intermodal loadings were 12,282,221 units, up 5.0 percent (588,709 trailers and containers) over 2005's 11,693,512 units, which had been the previous highest annual total ever. Also setting a record in 2006 was total freight volume, which was estimated at 1.74 trillion ton-miles, up 2.5 percent from the previous record which was set in 2005. December 2006 carloads on U.S. railroads were up 2.4 percent (29,608 carloads) over December 2005, while intermodal loadings were up 1.8 percent (15,871 units) for the month. For the fourth quarter of 2006, U.S. rail carloadings were up 0.9 percent (37,768 carloads) to 4,243,899 carloads, while intermodal traffic was up 1.4 percent (42,770 units) to 3,078,746 trailers and containers. Coal paced U.S. rail traffic in 2006. Carloads of coal rose 6.8 percent (35,257 carloads) in December 2006 to 552,568 carloads; rose 5.9 percent (101,153 carloads) in the fourth quarter to 1,822,877 carloads; and rose 4.7 percent (324,476 carloads) to 7,282,608 carloads for 2006 as a whole. In 2006, coal accounted for 42 percent of total non-intermodal U.S. rail carloadings. Carloads of chemicals rose 0.6 percent (619 carloads) in December, rose 0.8 percent (3,018 carloads) in the fourth quarter, and fell 1.1 percent (16,566 carloads) for the full year. In 2006, total chemical carloads of 1,519,261 accounted for 9 percent of total non-intermodal U.S. rail carloadings, second only to coal. Grain saw carloads rise 10.5 percent (8,689 carloads) in December, 6.5 percent (18,265 carloads) in the fourth quarter, and 4.3 percent (48,537 carloads) for all of 2006. Total grain carloads of 1,178,547 in 2006 were the third highest of any commodity category, behind coal and chemicals and just ahead of crushed stone, sand, and gravel (1,175,955 carloads). All told, of the 19 major commodity categories tracked by the AAR, eight saw U.S. carload gains in December, eight saw gains in the fourth quarter, and nine saw gains over 2005 for the full year.