| UP 3997 idles at the yard office in Tucson. 3997 is one of over 1400 SD70Ms Union Pacific owns, and is one of the 25 ex-SP units UP inherited in the 1996 merger. These units were built in mid-1994, and 3997 was originally numbered SP 9822. Behind the 3997 are two Ferromex SD70ACes, the successor of the SD70M. Ferromex 4056 was built in mid-2011 |