The railroad is growing more efficient during a period of soft demand.Union Pacific (UNP 4.71%) managed to grow net income in a flat revenue environment, and investors are taking notice. Shares of the railroad company are up 5% as of 2:45 p.m. ET after Union Pacific topped earnings expectations.Progress in a "challenging" marketUnion Pacific earned $2.69 per share in the first quarter on revenue of $6.03 billion, ahead of Wall Street's $2.52 per share on sales of $5.98 billion guidance. Operating income was ...