Wall Street Journal (Paywall, Jan. 11) -- A new federal rule allows U.S. trains to travel up to 220 mph, but no tracks can handle that speed. That’s due to several factors, including the difference in weight and crash standards between freight cars and passenger cars. The new rule will allow lighter passenger cars of 17 metric tons. Freight trains typically have a maximum axle load of 36 metric tons, according to Christopher Barkan, a professor of civil and environmental engineering and the executive director of the Rail Transportation and Engineering Center at Illinois.