Wall Street Journal (June 15) -- Freight trains are on track to stretch up to 3 miles long, with 200 cars or more. The trend is being powered, in part, by an unusual energy source: the activist investor. “Railroads thrive on economies of scale,” says Christopher Barkan, the director of the railroad engineering program at Illinois. “Longer trains are the most important advance in achieving economies of scale in the past quarter century.”