Union Pacific Corp. is nearing an agreement for a stock-and-cash deal for Norfolk Southern Corp. that would value the smaller rival at about $320 a share, people familiar with the matter said, in what would be the rail industry’s biggest-ever tie-up.

Railroad operator Union Pacific (UNP) is reportedly close to acquiring Norfolk Southern (NSC) for $320 per share in a cash-and-stock deal, which would give its smaller rival a valuation of about $72 billion.