The Union Pacific Railroad vs CSX Corporation spread seems to be a low volatility way to be bullish U.S. Dollar futures. The first chart is a correlation of the UNP vs CSX spread. You can see that it has been heavily trending since early April of 2011. The next chart is a daily chart to give you an idea of how correlated the UNP vs CSX spread is to U.S. Dollar futures. The last chart gives you an idea of how playing the UNP vs CSX spread smoothed out the volatility of holding an outright U.S. Dollar futures position.