Long term, carriers are in fine shape but unlike a manufacturer who can come out with a new / better product a railroad cannot "create" demand but can only take or lose traffic based on price and service. Should the economy stop expanding, traffic will surely drop. In fact in the latest report car owners idled more than 700 cars in July due to sluggish demand. This doesn't mean that trouble is certain - as of this writing the Dow Jones Industrial Average is up 1.5% for the day
Journal of Commerce