Future of Diesel Traction

Today, Electro-Motive Diesel, the Progress Rail/Caterpillar Company, delivered its last EMD Class 66 diesel locomotive for Europe. This gives me the opportunity to quickly reflect on the future potential of diesel locomotives:

The locomotive, also known as EMD JT42CWRM, was first built in 1998 and introduced to the UK as a major workhorse for heavy haul diesel traction. Since then, the 3300 hp strong locomotive contributes to the diesel operation across the UK. In particular beneficial for the operators was at that time the increased availability and reduced maintenance costs.

While the Class 66 met the Euro IIIa norms, it could only fulfill the Euro IIIb requirements with additional after treatment of the exhaust. This problem is faced by many other locomotive types in Europe and the US and is why I think, it is worth to have a look at alternatives solutions:

Stay with current diesel traction

The most obvious solution would be to stay with the current technology. Large and heavy diesel engines have proven quite reliable and rail proven. Electronically controlled injection and other improvements can certainly further improve environmental, economic and fuel efficiency.


  • Known technology
  • Not all optimization potential utilized


  • Costly in production and maintenance (specially trained people)
  • Heavy, leading to high wear and tear on the tracks


On the other side, electrification could be a solution, as the power can be locally produced (in Europe by wind, solar, but also nuclear power plants) and makes the operation independent of ever changing oil prices. However, the investment in electrified infrastructure can be quite high with the construction of substations, the foundations of the masts, catenary systems including copper wires. An electrification often makes only sense if there is considerable traffic on the route.


  • Potentially “green” energy
  • Cheaper and less “messy” operations
  • Less heavy locomotives


  • High investment in infrastructure
  • High investment in rolling stock
  • Often not sufficient traffic to make a business case

Multi Engine Solutions

The idea to use small diesel engines for providing heavy diesel traction is quite old. However, modern semiconductor technology and electronically management of diesel engine only enables the efficient utilization of this now. Bombardier has developed one of the first multi engine solutions for Europe for Germany, its success in terms of fuel saving and high availability is since some time undergoing commercial testing.


  • Operational efficiency (only engines in operation that are required for traction)
  • Fulfills high standards, e.g. Euro IIIb due to small engine
  • Alternative positioning in small carbody/loading gauge


  • Much more sophisticated electronic solution for management and operation necessary
  • Proven long term reliability of engines still partially outstanding.

Hybrid Locomotives & Last Mile solutions

From an operational standpoint, a solution that combines the advantages of the electric locomotives, with efficient operation under wire, while granting the flexibility of a diesel locomotive, by allowing to access harbor infrastructure or un-electrified lines would be ideal. However, these locomotives have just started to undergo their commercial endurance tests. The often small diesel engines, under 250kW have significant limitations when pulling a heavier train over a distance to a port or a factory. If a stronger and heavier diesel is selected, e.g. for NJ Transit, the locomotive becomes increasingly heavy decreasing the benefits significantly. Newer variants in the are of light freight locomotives or shunters are the Eam923 in Switzerland or the H3 in Germany, from Stadler, respectively from Alstom.

Alternatives with batteries as the second power source could prove to be an approach solving some disadvangates.


  • Maximal operational flexibility


  • High costs
  • Heavy
  • Do sometimes not meet the required emission standards

Other alternatives

Fuel cell locomotives and battery powered locomotives are currently looked at from various manufacturers. The increase in solar cell efficiency and decrease in price and weight will certainly also allow the development of independent cooling wagons or create energy for the HVAC, thus reducing the energy need from the locomotive. This might open up the market for less heavy and less strong locomotives, autonomous and in multiple traction.


The last word

One thing is certain, the last word is not spoken for a long time, the potential improvements in diesel and hybrid traction are many. The full electrification makes only sense when there is a reliable and green energy power source as well as the funding available.


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