Union Pacific , the largest U.S. railroad operator, said on Thursday it is in advanced talks with rival Norfolk Southern , signaling that a deal to form a $200 billion coast-to-coast rail company could be close - and potentially trigger further consolidation among remaining freight rail giants.

Stagnant volumes that have shifted to the trucking sector over the years appear to support the arguments for railroad consolidation.

CSX has a $62.5 billion market capitalization, compared to $58.7 billion for Norfolk Southern. Union Pacific is the largest of the three S&P 500 railroad stocks, with a $138.1 billion market cap. BofA also cited CSX's internal improvements in the upgrade, according to The Fly investment site.