WHEN RANDOLPH AND Mortimer Duke first explained the commodities market to Billy Ray Valentine in 1983, they laid out five examples: a cup of coffee, a piece of bread, some slices of bacon, a glass of frozen orange juice, and a few bars of gold…Had Eddie Murphy, Ralph Bellamy, and Don Ameche been filming that seminal scene of Trading Places today, they could have used another example, albeit one harder to fit on a breakfast table: truck routes.