Union Pacific 6936

Union Pacific 6936 is an EMD DDA40X locomotive owned by Union Pacific Railroad (UP). It is the sole example of the "Centennial" type that is still in operation, and thus is the largest operational diesel-electric locomotive in the world.

Union Pacific 6936
UP 6936 photographed near Watseka, Illinois, pulling a business train. UP 6936 as it appeared before the 2000 collision.
Type and origin Power type Diesel-electric Builder EMD Model DDA40X Build date January 1971
Specifications Configuration: ​  • AAR D-D Gauge 4 ft 8 1⁄2 in (1,435 mm) standard gauge Safety systems Leslie S3LR
Career Operators Union Pacific Numbers 6936 Nicknames "Centennial" Disposition Stored in Cheyenne, WY

Today, UP 6936 is stored in Cheyenne, Wyoming, at the roundhouse that hosts Union Pacific's steam program in preservation. It is part of the Union Pacific heritage fleet and is used on excursion trains and occasional freight trains.

Built in January 1971, the locomotive was as a DD40X rather than a DDA40X, as indicated by the model designation on the cab of the locomotive.[1][2] It served in revenue service over the next decade and into the mid-1980s across the Union Pacific system. UP 6936 made its last regular freight trip on May 6, 1985. Since then it has been part of the railroad's excursion fleet.

In November 2000, UP 6936 collided with a dump truck at a grade crossing in Livonia, Louisiana. The accident killed a railroad employee riding in the nose section and the driver of the dump truck. The unit was stored in North Little Rock, Arkansas, until damage to its nose could be repaired.[3]

The locomotive's most recent excursion was in 2015, when it helped the UP's trio of EMD E9 units at the annual Cheyenne Frontier Days event. It has not been used since, except on July 12, 2016, when helped to test UP 844, a steam locomotive being returned to service. Its dynamic brakes were used to simulate a load while being pulled.[4] After testing was complete, it was returned to storage at the roundhouse in Cheyenne, Wyoming.