The case for locomotive hauled trains and refurbishing old rolling stock

 This discussion arose from a YouTube comment.

“Keep operating super old locomotives is not exactly environment-friendly or even cost-efficient.”

This is true as a broad generalisation. However, the energy consumption of rolling stock and infrastructure has to be calculated over its entire life cycle, from mine to scrapyard. I cannot lay my hands on the figures, but I understand that at least a third of the energy consumed by a train occurs in mining and refining the raw materials and construction of the vehicles. Large amounts of energy are used to just to dig out and transport the minerals and convert the ore to aluminium metal, while aluminium welding is also an energy-intensive process. Aluminium mining is not environmentally friendly. Similar considerations apply to electrification infrastructure and battery technologies.

As regards cost, around a third of the total is for the capital costs of the rolling stock. This is usually reckoned to be fully amortised after 20 years, after which the costs are reduced to just the marginal costs of maintenance, overhaul and refurbishment. Since rolling stock has to be robust enough to withstand the arduous railway environment, it will last for 60 years with a mid life refurbishment. This is why we still see elderly trains in service, for example, locomotive types such as the British classes 20, 37 and 73, German class 232, the Swedish type RC, and various trains on London Underground. It cannot be economic to scrap serviceable rolling stock when replacement of some of the components is all that is needed.

“Newer engines can dramatically decrease energy consumption.”

Indeed. Trains such as the British IC 125 stock, the class 56 diesel electric locomotives and the class 73 electro-diesels have been fitted with new engines from EMD and MTU, which not only cleans up the emissions but also makes them more powerful.

“Besides if the train is too short, then using a heavy locomotive to haul it would cost a lot of extra overheads.”

It might, but a locomotive capable of hauling 3 carriages should not weigh more than about 70 tons, and the carriages themselves will be lighter as they will not have the heavy traction equipment built in. A slightly larger and heavier locomotive – say 80 tons, will be able to manage 6 coaches, of which some can be taken out of service when they are not required, and this is a useful opportunity to carry out tasks such as cleaning and maintenance. There is a further issue – the spread of on-train signal systems such as ERTMS. This is extremely expensive and has to be installed on every train capable of running independently. It makes economic sense to fit it all into a single vehicle – a locomotive.

“You can of course only hook for example 3 carriages to a loc, but that won't really decrease carbon footprints. A 3-car MU would draw much less power and use weaker but adequate engines.”

Railway operation accounts for 0.7% of total UK carbon emission. It isn’t even worth the effort thinking about it. However, if decarbonisation of the railways adds to costs or makes rail less attractive in other ways, then the result will be increased emissions.