By the turn of the 21st century, the diesel horsepower race was over. The third generation of freight engines had found its sweet spot: a six-axle, computer-assisted, 4000-4400 horsepower locomotive with a wide, comfortable cab. Railroads viewed this as the perfect building block for multi-engine lashups to power virtually any size train. Development of the next generation of power would be born not out of railroad needs, but due to government regulations.
On January 1, 2005, the Environmental Protection Agency's Tier 2 emissions requirements for railroad locomotives went into effect, significantly reducing the pollutants that diesels could exhaust into the atmosphere. Electro-Motive Diesel's SD70ACe, along with its General Electric rival, the ES44AC, inaugurated the fourth generation of diesel power in response to those regulations.
Rather than just upgrade its existing SD70MAC to Tier 2 standards, EMD took the opportunity to design a new locomotive from the rails up. Emissions turned out to be the easy part. Only slight modifications were needed to make EMD's 4300 horsepower model 710 motor meet new emission standards. With 5000 such motors in service worldwide and a reputation for dependability, EMD reasoned that shop crews would prefer familiar technology.
Other than the prime mover, however, virtually every element of the SD70ACe was re-thought to create a 21st century locomotive. Ergonomics were a prime consideration. The engine's angular nose offers the crew far better visibility than most other locomotives, and the cab is comfortable for engineers of almost any size. Digital screens provide a range of information on what is happening both inside the locomotive and out on the road. The cab easily accommodates a crew of three - an important factor in a modern world without cabooses. And there is, of course, a cupholder for the engineer.
The SD70ACe also offers, in EMD's words, "outstanding improvements in maintainability." All electrical wires are on the right side of the locomotive and all piping is on the left, with most pipes and wires routed under the frame so they can be serviced by a man standing outside the engine - rather than crawling around at the bottom of the engine room.
After a year of testing on the road and at the Association of American Railroads' test track in Pueblo, CO, the first SD70ACe's ('e" stands for "enhanced") were delivered to CSX Transportation in 2004. Six of North America's seven major Class 1 railroads, along with a number of smaller lines, ponied up to buy the new locomotives. When stricter Tier 3 emissions rules went into effect in 2012, compliance was relatively easy. By the end of production in 2014 - after new Tier 4 requirements dictated a new locomotive design - nearly 2000 SD70ACe's were and still are hauling freight across the U.S., Canada and Mexico.Did you know?
IntelliTrain, an option on the SD70ACe, uses cellular and GPS technology to allow a railroad's maintenance department to monitor operating conditions and problems as they occur out on the road - making diagnosis and repair considerably easier.