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In this world a nation has built 2 railway networks, a smaller 3'6" gauge network & a heavier 4'8" railway network. The 4'8" network connects most of the major cities & has very high American level axle loadings. It is built to enable up to 250kph running of ~40 meter long 4-6-4-4 locomotives with axle loadings of 33 tonnes & 5 cylinders, although they only do 230kph in regular operation. Think Pennsylvania Railroad class T1 with valves actually built for the speeds it can operate at & an extra driving axle.

Now at this point it's roughly the ~1960s-70s technology wise. Proper high speed rail is on it's way in with trains like the 0 Series Shinkansen & Intercity 125. This country now wants to convert it's 4'8" heavy axle loading railways towards more conventional HSR away from the old steam haulage.

But most HSR trains have relatively low axle loadings, however that's mostly to reduce infrastructure requirements. But in this case the infrastructure was already built for very very heavy axle loadings at the same time as high speed operation.

So the question is here, within the limitations of 1960s-170s technology, what could be done to take advantage of very heavy axle loadings on HSR lines?

Other things:

  • There's about ~800km of track in this network.
  • The government is willing to pour a lot of money into this
  • Increasing track speeds beyond about ~250kph isn't an option, they don't want to do significant track work beyond electrification & would like to avoid even that if possible.
  • Due to the network being being built for extremely long locomotives bogies aren't 100% needed but preferred
  • The network is all 3 track lines aside from lower speed branches
  • Freight trains do share the tracks & vary in speed significantly
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  • $\begingroup$ Whatever possessed them to create such a massive and overbuilt railway in the first place? $\endgroup$
    – Cadence
    Jul 29, 2023 at 7:27
  • $\begingroup$ @Cadence they wanted to go as fast as they could but the limitations of the technology meant going big. Also the PRR T1 had not much lower axle loadings (32.5 tonnes) & a top speed of 230kph & actually existed so. (It doesn't have the locomotive speed record because the US didn't fit speedometers to locomotives back then) $\endgroup$
    – OT-64 SKOT
    Jul 29, 2023 at 8:37
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    $\begingroup$ (1) I don't understand what they want to do. The question says that the track supports heavy trains running at 250 km/h, and they want to replace it with lightweight trains running at 250 km/h? That a no-operation. They don't have to do anything. (2) 800 km of track is nothing. That's a network of urban tramways, not of railways. (For example, Melbourne has 245 km of tramways.) The United Kingdom had 7000 miles (11,000 km) of railways in $\rightarrow$1850$\leftarrow$. Romania has 11,000 km of railways. Our port of Constantza has 300 km of internal railways. $\endgroup$
    – AlexP
    Jul 29, 2023 at 12:16
  • $\begingroup$ What is the average speed of the freight trains? One assumes the "230kph in regular operation" is for passenger. Also, it looks like you are saying that the new passenger trainsets will be lighter but not significantly faster ("Increasing track speeds beyond about ~250kph isn't an option") -- is that accurate? $\endgroup$
    – user535733
    Jul 29, 2023 at 13:06
  • $\begingroup$ @user535733 The freight trains vary in speed massively as a lot of different types of freight are being moved. Yes, the trains are not going to be able to go significantly faster. The main point of the question is asking if there would a reason to build heavier HSR trains than what we see IRL. $\endgroup$
    – OT-64 SKOT
    Jul 29, 2023 at 13:18

2 Answers 2

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The train could use double-decker rolling stock.

For a truly epic plan, have a look at Hitler's Breitspurbahn or broad-gauge railway. This never got beyond the planning stage, but it had over a hundred railway engineers on it, and was thought feasible at the time.

The logic was this. They had inherited a railway system with miles of double track. Much of this was in poor repair. The plan was to replace the double lines with a single 3 meter wide track. In this case, the actual railway ballast and sleepers, which were in poor repair were to be replaced by a concrete trough structure. The lack of separate up and down lines was cured by 'passing places' perhaps two kilometres long.

The broad gauge could not be used everywhere. It was only intended to replace the main lines where there were long, straight stretches of double line. But that allowed them to plan with one line that went from Brest to Paris, Berlin, Warsaw, Moscow, Vladivostok, Fairbanks, and on to New York. Other branches went to Rome, Madrid, Istanbul, Iran, and India.

People questioned what the huge railway would carry in peacetime. Part of its job was probably political: it was to unify the new empire.

It might have looked a bit like the railway in 'Girl Genius'.

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"The main point of the question is asking if there would a reason to build heavier HSR trains than what we see IRL."

In real life, we do see differences in the weight of HSR trainsets due to regulatory differences.

The US Federal Railroad Administration uses a different buff strength test than most other jusridictions:

  • USA: 800,000 lbs / 3.0 MN vs. EU: 450,000 lbs / 2.0 MN

The added structure to meet this test currently adds about 3% to the weight. The axle loading of two members of the Avelia HSR family:

  • Avelia Liberty (USA): 17 t vs. Avelia Horizon (EU): 16.5 t

Your world can have even stronger crashworthiness regulations, justified perhaps by the mixed traffic. Or a record of dispatch/signal failures. Or other risk management choices. That will make the HSR sets heavier.

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