Over 1,100 were built, with only 25 built specially for Conrail and over 350 built for the Burlington Northern (with orders continued into the BNSF merger with another 800 or so units ordered later on). Later customers such as CSX,and the Alaska Railroad (ARR) as well as TFM (subsidiary of KCS; Kansas City Southern) eventually purchased units up until the introduction of the SD70ACe.
The SD70ACe serves as the SD70MAC's successor; having more advanced microprocessor controls and being EPA Tier 2 compliant.
Many are still currently in service, with the exception of several stored, wrecked, and a few retired units.
During the early-1990's, EMD teamed-up with German engineering company Siemens to experiment with having an average, modern, North American type of freight diesel locomotive to become capable of providing AC-traction drive currents, and thus providing a high-horsepower rating and lower fuel consumption for railroads which had an ever-increasing demand for saving fuel consumption by using a lesser amount of units to haul most of their trains. The solution to all these problems was resolved with the experimental SD60MAC, which proved to be an initial success after several demonstrations with the Burlington Northern's Powder River coal trains through Wyoming and Montana. Because of the success of the SD60MAC, the development for the SD70MAC first A.C. production locomotive built by EMD. Although the SD60MAC was successful, the BN; however, disliked the cab design due to being uncomfortable with rail employees who tested the units. Such complaints consisted of: heavy vibrations, noise pollution from the prime mover, and an unusual amount of cab visibility due to the cab design originating from an earlier SD60M, yet with a slightly different window placement which deemed to be too "foreign"; meaning that the design looked more Canadian, and such design was originally disliked by employees who drove some of BN's earlier SD60M units ordered and received several years earlier.
The EMD SD70MAC was first introduced in early 1993, and began production later-on during the same year after numerous tests and improvements were made. The first order was 350 units were received from the BN in mid-1993 to late-1995. BN eventually began to slowly replace their fleets of aging SD40-2 units (aside from their GE U30C and Dash 7 units) assigned to their Powder River Coal Trains in favor of their new, modern, high-tech AC-traction SD70MAC units; which were proven to replace 5 SD40-2's on an average coal train, with only 3 to 4 being necessary (two front, two rear) with the SD70MAC units having a DPU (Distributed Power Unit) capability, which was originally introduced with the SD60MAC.
Towards the end of the SD70MAC's introduction, a new rival from GE appeared: the AC4400CW, which completely dominated over the SD70MAC in production sales. Although more successful in popularity, the AC4400CW had more short-lived warranties with most railroad's fleets which had to be renewed unlike the SD70MAC; hence the reason why the Burlington Northern decided to deny every opportunity from GE due to already having numerous warranties from leasing companies which required numerous payments.
Today, the SD70MAC can still commonly be seen hauling various coal trains or being assigned to coal drag service on the BNSF, as well as being a common hauler on the TFM portion of the KCS (Kansas City Southern). Former Conrail SD70MAC units can still be seen on the CSX system, yet no longer bear or wear their once-exclusive livery which was very similar to their SD80MAC livery, while the Alaska Railroad's fleets of SD70MAC units can be seen in general revenue service on both of their freight and passenger trains (being the only US Class 2 railroad to actually have both revenue freight and passenger service).
Who bought what?Edit
ARR: (QTY:26), #'s 4001-4016, 4317-4328. The second order's units are Tier 1 compliant and have HEP generators. Four units were built in 2007 on exemption credits.
BN: (QTY:350) #'s 9400-9749. First order for SD70MAC, all convayed to BNSF in 1995.
BNSF: (QTY:786) #'s 8800-8989, 9400-9499, 9504-9999. #'s 9400-9499 and 9504-9716 are Ex-BN.
CSX: (QTY:220) #'s 4500-4589,4701-4830. 4575-4589 are Ex-Conrail.
KCS: (QTY:75) #'s 3900-3973. Note there are numbering not consecutive. All Ex-TFM.
Conrail's SD70MAC fleet was originally meant to be compatible with their SD80MAC fleet as well, yet their SD70MAC's commonly served as helper or DPU units on trains led by SD80MAC units.
CSX's SD70MAC fleet primarily consists of all 25 former Conrail units, and over 200 more units.The SD70MAC was the last type of locomotive ever purchased by the Burlington Northern before merging with the Santa Fe (ATSF) in 1995-1996, which also wore a short-lived exclusive paintscheme which was also applied to their executive fleet of preserved F Units and coaches from their predecessor's heritage.
Although the BNSF merger continued into 1996, EMD still applied the BN's exclusive "Cascade Green" scheme to BNSF's new orders of SD70MAC until the introduction of the Heritage 2 paint.
BNSF's later SD70MAC units had different headlight and handbrake placements as opposed to their earlier pre-merger/post-merger BN SD70MAC units.
Only four SD60MAC units were built, with only one remaining in storage as of 2012.
BNSF 9647; the "Vomit Bonnet", was painted in an exclusive livery to commemorate the success of the BNSF merger, and actually demonstrates an experimental paint. BNSF 9647 is now in H3 paint as of late April 2013.
Only a handful of SD70MAC units have actually been painted into BNSF's new H3 ("Heritage 3") paint.
ARR #4001 was actually applied with a unique dedication known as the "Spirit of Alaska", similar to CSX's "Spirit Of..." units. 4002-4015 are named after cities along the right of way, starting at Seward and heading north.
P&L Transportation, Inc. (Paducah & Louisville Railway [PAL], Evansville Western Railway [EVWR], and Appalachian & Ohio Railroad [AO]) acquired 16 former CSX SD70MAC units in 2013 from CSX. These are the first AC traction locomotives to be sold to a Class II railroad.
Alaska Railroad aquired 4 Tier 1 SD70MAC;s in 2007 on exemption credits, these locomotives also have HEP generators.