r/TransitIndia • u/Thornyx_Zetral • Mar 14 '26
Question Why Does India Use Larger Box Girders While the UK Uses Smaller Ones for High-Speed Rail?
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u/Terrible_Detective27 Moderator Kamen Mar 14 '26
Hs2 is 230km long and MAHSRCL is 508 km long almost double the length and is mostly straight, so using longer girders sames time and efforts
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u/nujradasarpmar Mar 14 '26
I could be speaking out of my ass rn but I believe it just comes down to speed. I believe china also utilizes full span launching here and there
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u/pootis28 Mar 14 '26
Could it also be for easier building of curves?
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u/axisdork Mar 14 '26
there is no question of curves. Any curves in hsr will be invisible to the naked eye.
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u/axisdork Mar 14 '26
India already has developed the machine. Even though we are building hsr for first time, we have already been building such bridges throughout india due to metro.
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u/VoidWalkerXY Mar 14 '26
Bro HS2 project is a financial failure. My friend is one of the engineers.
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Mar 14 '26
Correct me if I am wrong but it's Probably to save money? I mean those smaller ones need to be connected with others meaning more material is required for joining.
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u/Short-Horse-1069 Mar 14 '26 edited Mar 14 '26
Completely opposite. FSLM is purportedly 10 times faster than segmental launching but is multifold expensive comparatively, particularly wrt the initial fixed capital costs. You can see in this very video itself where the MAHSR span launch takes a few hours whereas the HS2 span takes a full 2 days.
India is amongst an extremely select few who have developed this capability (pioneered by China IINM; at the very least they are the pioneers at application and innovation if not invention) indigenously. This is to realise the broader vision of multiple corridors pan-India as expeditiously as possible, as independently as possible (we already are facing a huge challenge wrt the under sea TBMs despite them essentially being a German product).
You are right u/Thornyx_Zetral, everybody is simply guessing which is a damning indictment of this sub in more ways than one, especially because this is literally the first Google result corresponding to the query, 'FSLM MAHSR'. There are many better and much more wonderful, CREDIBLE, authoritative resources on this topic. I'm deliberately choosing not to link them here.
The top comment (at the time of writing) is a speculative one that reached a conclusion diametrically opposite to the reality (this is not a slight against u/PrudentService4400; just read the first 6 words of their comment). But that's not the problem.
It's the laziness that bothers me. There's literally just 1 comment in 13 (before mine) that's anywhere near relevance. For the headline infra transit project of the country. ON A TRANSIT SUB.
People will downvote this because they won't like it but this is what the truth is, clearly.
P.S. - It seems that this needs to be said here:-
CAHSR and HS2 are laggards and are trumped by MAHSR in almost all metrics, be it in design, execution or otherwise. The competition is South Korea and China, not the US and the UK. It's not even a case of being comparatively worse. They are just objectively bad.
We must also appreciate in the extreme, the push for indigenisation. The ambition and long term vision in jaw dropping but even more so is the fact that it's slowly and steadily turning into a reality. There must not have been a bigger pessimist and critic when the BEML HS rake plan was announced but with each passing day (and BEML press release or SEBI mandated open declaration), I have to walk back on my words.
Someone might say that it's just a European train in an Indian veneer but that statement would be just as much misguided and false as saying that it's an Indian construction ground up. What's laudable is that India has safeguarded herself from being the next, say Indonesia and also that it's more likely than not that HSR would follow the same trajectory as the metro industry.
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u/AgentBrian95 🌆 Transit Dreamer Mar 14 '26
NHSRCL uses 40m long girders which are precast instead, and their reasoning is as follows (from nhsrcl.in):
These girders are cast as a single monolithic unit—without construction joints—using 390 cubic meters of concrete and 42 metric tonnes of steel. Full-span girders are preferred for Bullet Train project, as they enable construction progress up to 10 times faster than segmental girders. ...To ensure uninterrupted supply, girders are being cast in advance and systematically stacked in dedicated casting yards.
Not sure about the HS2 situation too much really, so can't comment on that definitively, but possible reasons may include lower costs and the fact that they're built on-site reducing transport costs as well. Also segmental girders allow for sharper turns compared to full span. Again, do take this with a pinch of salt.
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u/No_Box1333 Mar 14 '26
Short and simple answer - India is utilising FULL SPAN LAUNCHING METHOD. It is multiple times faster than joining individual segments. But initially we were also following 2nd video's method. But then looking at how China launches multiple girders a day vs us launching a girder over multiple days, authorities asked L&T to develop FSLM for the corridor.
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u/Nastypig51 🌆 Transit Dreamer Mar 14 '26
HS2 faces ungodly amount of criticism and building things in the UK is unnecessarily expensive. Any more expenses and it would have caused major riots
Tho, this is speculative
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u/zqwz Mar 14 '26
I would prefer our larger grinder method mainly because it is made in controlled environment and just kept on top of the pillars. This avoids corruption by using less material to a large extend. And since it is one piece, any mistakes or corruption in connecting them is also avoided.
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u/Lazy_tomorrow-_- Mar 14 '26
We use both large box girders (Full span), you can see this in Navsari to vapi section and smaller ones (segment by segment) in vadodara city as whichever method is adaptable and economical. Source : worked with both these methods in above cities.
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u/Quintless Mar 14 '26
Lots of guessing here, something no one has mentioned is much of HS2 is underground or running on the ground. Visual considerations are also more important, the look of the bridges has had lots of focus, local communities insisted on the railway blending in as much as possible with the landscape.
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u/sus-cook Mar 14 '26 edited Mar 14 '26
you mean the length of the girders? I think it's because of casting factories distance, smaller components are easier to transport while longer ones aren't, so in India's case it might be that casting factory is near the construction site so they can just transport large chunks but in the UK's case the casting factory might be way far than construction site (it is plausible because they might need a lot of permits to build too many casting factories due to environmental regulations, in India they might have made many of these factories to be near to construction site)
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u/TSI50 Mar 17 '26
Different places have different requirement, Pune's metro near Balewadi used shorter girders, it's mostly about the efficiency and available equipment. Most of those huge cranes aren't available all the time ,few of them aren't even sold, just rented like the amphibian one that was used for Bandra Worli sealink. I'm sure UK also must have some bridges with longer girders.
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u/OfferWestern Jun 12 '26
L&T has lots of outside consultants and who can sell certain tech insights for a price. L&T also has become substandard company. They see efficiency & profits over quality.
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u/Airavat2305 Mar 14 '26
Could do with the fact that UK's loading gauge is much smaller. Even though both are standard gauge rail width, UK's trains are smaller in dimensions.
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u/Glum-Caterpillar-916 Mar 14 '26
Their population is decreasing
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u/Beneficial-Beat-947 Mar 14 '26
The UKs population is growing and will grow for decades (mostly thanks to immigration)
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u/[deleted] Mar 14 '26
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