5. CSX

CSX is Class I railroad in the U.S. Buffett is an ardent believer of railroads too as Berkshire Hathaway acquired BNSF Railway in the year 2009. Buffett quotes, “A little math will tell you that about 15 percent of all inter-city ton-miles of freight in the U.S. is transported by BNSF. It is no exaggeration to characterize railroads as the circulatory system of our economy. I couldn't find a comparable statistic for CSX's market share but with more than 21,000 route-miles and a fleet of more than 80,000 freight cars, rest assured that CSX is no slouch.”