Here is an excerpt from a Reuters article from today.
In the last couple of years steam coal volumes slumped significantly as natural gas prices dropped. Now that traffic has returned and the government stamps its foot and says, "Move the traffic!" This contributes greatly to the success of a private company as it clears away the backlog and invests millions of dollars in track and infrastructure.


"Demand for PRB coal has been much stronger than the railroads were prepared to handle and stronger than utilities had expected going into this year", said Ted O'Brien, president at coal analytics company Doyle Trading Consultants in New York, referring to coal from the Powder River Basin, the source of about 40 percent of U.S. coal supply.

Railroads are also handling rising shipments of oil and of grain, limiting their capacity to ship coal.
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While railroads are buying more locomotives to ease bottlenecks, analysts and investors said problems are likely to persist until the end of the year.

Reuters