NEW YORK (Standard&Poor's) May 6, 2014--Standard&Poor's Ratings Services said today that it has assigned its 'AA' rating to Union Pacific Railroad Co.'s 2014-1 Pass Through Trust. Union Pacific Railroad is a wholly owned subsidiary of Union Pacific Corp. (Union Pacific; A/Stable/A-1). The company is using the debt, commonly referred to as equipment trust certificates, to fund the purchase of locomotives. We based our rating on preliminary terms and conditions, and it is subject to legal review of final documents. Union Pacific, an Omaha, Neb.-based freight railroad, has about $12 billion of lease-adjusted debt. "The certificates benefit from special protection under Section 1168 of the U.S. Bankruptcy Code and are rated one full category above the corporate