Incompatible HSR (Japan etc)

Hello,
I was having a look at some of the off topic Maglev discussions here, and that got me wondering. The main benefit cited for conventional HSR over the Maglev alternative (the likes of Transrapid etc) is the compatibility with the existing network, which is a reasonable trade off for some minor speed losses (plus the cost difference).
However, that didn't stop the Japanese building HSR at a different gauge to the rest of their network. What was the reasoning there? narrow gauge not able to sustain the needed speeds? Could this be repeatable elsewhere?

Speed43125 said:

narrow gauge not able to sustain the needed speeds?

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My understanding is 'Yes', and of course they are built to a larger loading gauge so more spacious carriages etc.

In a densely populated country they wanted/needed a late 20th century 'inter urban' passenger railway rather than a 19th century one.

Yes, certainly at the time the SKS was planned, the JP-narrow gauge could not offer speeds above 150/160 Kms/hr. Plus that the ng was mostly chosen there due to the mountainous landscape, just as f.e. in parts of CH=Switzerland, see that most of SKS is on viaduct or in tunnel to straighten the curves out. They now plan a new super-high-speed line besides the 2 on the main corridor, and there were long talks about it being a MagLev or so, so without real rails and thus adding a 3d type of structure.
Incidentally, I just read that ID=Indonesia is now (restarted) building a normal gauge HS line on Java beside the conventional meter gauge.
TH=Thailand, linking up to CN=China, via hitherto railless Laos (yes, I know it had a few Kms somewhere else) will also use the std g. for this link besides its normal meter, as does/did China itself on the long stretch south of Kunming toward Lao border, the old Yunnan railway towardVN=Vietnam (which was already abolished before the HS-line started being built).
Not sure, but perhaps the same applies to the also CN-built new lines in Africa, like Kenia and Ethiopia, although these are not really HS, just fast.

As well as achieving higher speeds, one of the original objectives of the Shinkansen network was to increase capacity. The Tokaido mainline was a two track railway that was full, and slow because of conflicting stopping patterns. It was also not possible to increase capacity on the alignments that had been chosen many years earlier. At that time, Maglev wasn't an option. But equally, they took a strategic decision that interoperability with the legacy network was not only not necessary, but undesirable. So that gave them free rein to choose a system that they considered optimal - settling on a standard track gauge, wide loading gauge and largely viaduct construction, to keep the trains away from potential causes of accidents and delay.

Spain is of course the reverse of Japan, with standard gauge HSL (LAV) replacing/supplementing classic broad-gauge (1668mm) lines.
Some sections been laid with broad gauge but with the intention to narrow to standard when there is a connection to the main HSL route (eg Santiago-Orense).
Others have been laid with mixed gauge to meet all eventualities (eg Valencia-Castellon).
The penalty is the need for gauge changers at points where the two networks meet, but Spain has become market leader in the technology, now fully automated.
With the right bogie design, trains just pass slowly through the gauge changer, switch power and signalling systems as well as track gauge and carry on.
I think the broad gauge is limited to 160km/h, mainly because of the ASFA signalling system used by Renfe.

There is now at least one mixed-gauge section in Japan used by smaller-profile Shinkansen trains.

Having decided not use their existing gauge, the Japanese had a totally free choice on what gauge to choose. It's interesting that they should have gone for 1435mm when many people suggest that the optimum would be a bit wider (and this is one reason I disagree with that idea). They may of course have been thinking of export potential, and they did indeed sell some high speed trains to Taiwan.

The conventional rail network in Taiwan is 1067 mm gauge, like in Japan, and most of it was built when Taiwan was colonised by Japan (1895-1945). This means that Taiwan High Speed Rail is a separate, self-contained system just like the Shinkansen.

The Shinkansen's origins lie in plans during the Second World War to build standard gauge freight lines, which would have eventually been linked by a tunnel to Korea, which was a Japanese colony. The standard gauge network in Korea was in turn linked to the South Manchurian Railway in Japanese-occupied Manchuria. The route of the Tōkaidō Shinkansen includes a few tunnels built during the 1940s for the original Shinkansen project.

edwin_m said:

There is now at least one mixed-gauge section in Japan used by smaller-profile Shinkansen trains.

Having decided not use their existing gauge, the Japanese had a totally free choice on what gauge to choose. It's interesting that they should have gone for 1435mm when many people suggest that the optimum would be a bit wider (and this is one reason I disagree with that idea). They may of course have been thinking of export potential, and they did indeed sell some high speed trains to Taiwan.

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Yamagata and Akita branches from the JR East Tohoku trunk line heading north from Tokyo follow the alignments of former narrow gauge lines that have been re-gauged to standard using smaller rolling stock than the captive trains that routinely operate on the rest of the high speed network. These are known as 'Mini shinkansen' routes and they share the alignments with other local traffic, either by means of dual gauge sections or by conversion of the local stopping train service also to standard gauge. The long undersea Seikan Tunnel, connecting the islands of Honshu and Hokkaido, also carries dual gauge tracks. Standard gauge Shinkansen passenger trains share the tunnel with narrow gauge freights in that case; there are no longer any narrow gauge passenger trains using that link.

https://en.wikipedia.org/wiki/Mini-shinkansen

Mini-shinkansen (ミニ新幹線) is the name given to the concept of converting 1,067 mm (3 ft 6 in) narrow gauge railway lines to 1,435 mm (4 ft 8 1⁄2 in) standard gauge for use by shinkansen train services in Japan. Unlike the high-speed shinkansen lines, the mini-shinkansen lines have a maximum speed of only 130 km/h (80 mph). Two mini-shinkansen routes have been constructed: the Yamagata Shinkansen and Akita Shinkansen.

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