July 2013    There are thousands of big-rig accidents in the continental United States every year. And no wonder - America's roads are among the busiest in the world, and the vast majority of America's shipping takes place on the asphalt highways that bind the nation together. Sometimes these are terrible accidents near major cities, crashes that lead to multicar pileups or dangerous chemical spills that force evacuations of whole neighborhoods. These make all the papers. The small crashes, th