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Today’s Heavy Haulers

Part I - The EMD SD70-Series

All Photographs by Jack Hykaway


Travel westbound on Interstate 94 in North Dakota and one can’t help but notice the vastness of the rolling plains.  The old Northern Pacific (NP) mainline follows a meandering route around the hills while the highway undulates with the terrain.

Very little variation to this wavy landscape is noticed until one reaches Bismarck - the state capital - where the mighty Missouri River cuts through the plains at the bottom of a deep valley.  The highway drops quickly down to the valley floor, while the NP mainline curves through downtown and crosses high above these waters on one of the city's most recognizable structures.  Three enormous trusses provide for the BNSF what they did for the NP and the Burlington Northern: a reliable link between East and West.
Standing below the bridge, the blue waters of the river tremble in the breeze.  The smell of creosote ties emphasized because of the day’s 40-degree (104-degree Fahrenheit) summer’s heat wafts down from the bridge deck high above my head. 

Suddenly, pigeons resting on the trusses above rush off of the structure, flying away just as the sounds of roaring EMD 710 prime movers overcome the sound of crashing waves from a passing boat.  Two big locomotives emerge out of the trees on the opposite bank and move across the steel spans, which date back to 1905.  Their angular noses are intimidating and their mean look accurately represents the sheer power and size of these locomotives.  This pair of SD70ACe locomotives – two ofEMD’s most modern units – is still roaring in notch eight, slowly lifting a heavy unit coal train out of the valley.

As the locomotives pass high above, I can feel their immense sound shake my bones, and their immense power shakes the riverbank below my feet.  These modern AC-traction EMDs are used by the BNSF and other Class I roads on heavy unit trains, including on the many coal trains originating in the Powder River Basin in Wyoming, some of which pass via Bismarck. 

SD70: The Rebound That Saved EMD

In the late 1980s, EMD was struggling.  After the production and commercial failure of their unreliable SD50 locomotive series, EMD’s once-polished reputation was severely tarnished.  Once the dominant locomotive manufacturer in North America, the failure of the SD50 opened the door for rival manufacturer GE Transportation to step in and take over that prestigious number one spot.

EMD, scrambling to regain momentum and their customers’ trust, launched the SD60 series of locomotives. These diesels were purchased by several roads and were much more reliable than their SD50 predecessors. The SD60s helped EMD close the gap between its sales and those of GE.

However, it wasn’t until the early 1990s when EMD released the first of the SD70 series of locomotives that the manufacturer started to regain steam.  The SD70 (and its variant models), developed in response to GE’s new – at the time – Dash-9 series of locomotives, was an immediate hit among North American railroads. 

One large reason for their success was the introduction ofEMD’s HTCR radial (steerable) trucks.  Instead of following the rail, the trucks could steer themselves around the curve.  This reduced wear-and-tear on the rails and the locomotive’s wheels, and it slightly increased tractive output around the corner.  This steerable option – which GE does not offer (even today) – is still a significant reason that railroads purchase new EMD 70-series units over their GE competition.  Another important selling point is the new, easily-maintained computer and microprocessor systems on board.

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The Variations

To cater to different preferences of North American carriers, EMD produced – and still produces – a number of spinoffs to their basic SD70.  Though the mechanical and electrical aspects of these variations are nearly identical – with the newer SD70M-2, SD70Ace, and SD70ACe-T4 being exceptions due to significant technological advancements at the time of their conception and stricter emissions regulations – they all have subtle differences.

The SD70I model is unique to Canadian National.  The “I” in the model name designates that these locomotives are fitted with EMD’s isolated cabs, called Whisper Cabs.  These cabs are isolated from the vibrations and noise generated by the unit’s prime mover.  These cabs are a favorite among locomotive crews because of their smooth ride and quiet interiors, though, rather surprisingly, this feature has not been as popular with other railroads.

Union Pacific was a major purchaser of the EMD SD70M, which has a wide-cab fitted to its frame. The wide-cabs (sometimes referred to as comfort cabs) accommodated train crews more comfortably while the wider nose provided an increased level of crashworthiness in the event of a collision.  This has been the most successful SD70-variant ever produced – even more successful than the base EMD SD70 model – with approximately 1,500 units manufactured (1,400 of which were purchased by the Union Pacific).

The closest relative to the SD70M is the SD70MAC.  Their only difference is found in their method of propulsion; the SD70M uses DC current to drive its traction motors while the SD70MAC is fitted with AC traction motors on each axle, and therefore these locomotives use alternating current to power their wheels. The SD70MAC has been very popular for use in heavy-haul situations; their AC traction motors can handle slow speeds at full power while their DC counterparts are prone to burn-out under that load. Burlington Northern was a large purchaser of these locomotives for use in unit coal train service, and many still roam the rails under BNSF and PRLX ownership today.

As technology and locomotive efficiency improved, EMD released two models meant to succeed their aging SD70M and SD70MAC fleets.  The SD70M-2 replaced the SD70M and featured an angular look with a rectangular nose and largely flared radiators at the rear, the same features are found on the MAC’s successor the EMD SD70ACe. 

The only difference between these two models is (once again) found in their methods of propulsion; the SD70M-2 uses DC traction motors while the SD70ACe is fitted with AC motors.  While the SD70M-2 had only three major buyers (Canadian National, Norfolk Southern, and Florida East Coast Railway), the SD70ACe has been much more popular thanks to its more favorable AC-traction system.  The SD70ACes, much like their predecessor, were quickly pressed into heavy-haul unit-train services across the continent.

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SD70s For The Future

In 2017, in response to strict new emissions regulations put in place by the EPA in the United States, EMD released the latest member of its SD70 family.  This monstrous locomotive – named the SD70ACe-T4 – is EPA Tier 4 compliant and has been purchased only by the Union Pacific at the time of this writing. EMD-owned SD70ACe-T4 demonstrator locomotives have been testing on numerous Class I railroads across the United States and on both the Canadian National and Canadian Pacific in Canada.

EMD has seen large success from its line of SD70 locomotives, and, although not enough to secure them the spot of the leading locomotive builder in North America (GE still holds that title), we’re seeing shades of EMD’s very successful past.  Next time you’re trackside, keep an eye out for the distinct lines of an EMD SD70 product; you never know which type of SD70 you’ll see next!

For more information about EMD’s SD70 series, please visit these links:



About the Author


Jack Hykaway is a student, currently attending a post-secondary institution in his hometown of Winnipeg, Canada.  He is an amateur videographer and writer and enjoys exploring and documenting nearby railroads and railroad operations in both written and visual formats of his work.



Jack’s main focus of late has been producing his column Jack's Junction for The Modeler’s Journal.


Follow along with Jack's videography on his YouTube channel at



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