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DOUBLE DIESELS

I think it’s fair to say that Union Pacific has never been shy when it comes to loading up their trains with plenty of muscle. In fact, some railroad writers in the past have proclaimed that “U.P.” stood for “Unlimited Power!” The railroad’s desire for high horsepower goes well back into the steam days, when they marched 4-6-6-4 Challengers and 4-8-8-4 Big Boys up and down Sherman Hill. They were no less enamored with big diesels, rostering ALCO’s only three Century 855’s produced. They were 5500-horsepower monsters riding on eight axles. General Electric provided a fleet of 5000-horsepower U50’s in six-axle and 8-axle versions. It was EMD, however, who weighed in on top with their 6600-horsepower DDA40X, which Union Pacific dubbed “Centennials” and numbered them in the 6900-series to celebrate the 100th anniversary of the Transcontinental Railroad. All of the above-mentioned locomotives featured two diesel power plants under the hood, but in their absence, UP was just as happy to throw eight, nine or even ten or more smaller units on the front of their trains.

BIG TRAINS

Today, the average locomotive produces about 4500 horsepower with only a single diesel prime mover and it rides on six axles. Standardization has replaced the wide variety of motive power rolling out of the construction halls of a half a dozen builders. The magnitude of the trains themselves has increased, with many freight cars carrying 120 tons. Modern operating plans have resulted in fewer trains, but with longer consists and they often tie two trains together. You can now find many Union Pacific trains battling across Wyoming with well over a hundred cars, and engines on the front, middle and end of the train!!!

So, while the days of the double-diesels appear to be gone for good, there is still a lot of high-horsepower railroading to be seen — especially on the expansive Union Pacific system. Below I have assembled a complete list of GE, EMD and ALCO double-diesel road switchers. Union Pacific and Southern Pacific are the only two U.S. railroads to have ventured into the high-horsepower double-diesel market for road freights. There have been thirteen DDA40X’s preserved, with Union Pacific currently operating DDA40X #6936 in their Heritage Fleet. Unfortunately, the other double-diesel models have all been scrapped — there are no surviving examples of those unique U50 rounded cabs.