High speed trains with level boarding from 915mm platforms

[Nottingham59]

Is it possible to design a 360km/h high speed train that would allow level boarding from GB standard platforms at 915mm above the rail? What compromises would be needed compared to the current HS2 design?

According to Rail Engineer, the 360km/h Alstom AGV was the "reference train" that HS2 used so that its specification was based on "proven technology". The AGV has a floor height of 1155m, which seems to be why HS2 Ltd specified a standard platform height of 1115mm above the rail for platforms on their network. "The HS2 Platform will have the following dimensions:  Height: 1115mm above rail level; and  Offset: 1655mm from track centreline" from the HS2 Train Technical Specfication https://assets.publishing.service.g...E-000-000007_P11_TTS_Main_Body__External_.pdf (See section 7.5 for Access and Egress)

So could HS2 have specfied 915mm platforms and still had trains capable of 360km/h? Would smaller wheel diameters be feasible? Or pockets cut into the floor of the train to accommodate the top of AGV diameter wheels? (I can't find what diameter AGV wheels are, but the TGV standard is 920mm) Would that compromise door positions or level access between carriages? If not, what speed would have been compatible with 915mm level boarding?

Any thoughts? Thanks

 

[Bletchleyite]

Just drop it between the bogies in a couple of vehicles with wheelchair spaces. Then you don't need smaller wheels etc.

 

[Nottingham59]

Just drop it between the bogies in a couple of vehicles with wheelchair spaces. Then you don't need smaller wheels etc.

You mean having a sort of undercroft in the middle of one coach? It could work, I suppose, but it would interrupt step-free access along the length of the train. And would force the doors away from the bogies which would lead to huge gaps on curved platforms. Maybe in each driving car, so there's one at each end of unit?

 

[Bletchleyite]

You mean having a sort of undercroft in the middle of one coach?

Yes. It's a common European approach.

It could work, I suppose, but it would interrupt step-free access along the length of the train.

I'm not sure this is that important (provided some sort of workaround for the trolley is provided, if there is one).

And would force the doors away from the bogies which would lead to huge gaps on curved platforms.

Only to thirds, which plenty of stock has anyway.

Maybe in each driving car, so there's one at each end of unit?

That might not be a bad idea, as it avoids the trolley being obstructed, and would allow one in each class.

 

[dm1]

I'm fairly certain you can get level boarding at 915mm for a high speed train without needing to majorly compromise on bogies. The Stadler SMILE platform is designed for 250km/h with level boarding at 780mm, for example.

The same design allows for level boarding at 550mm as well using exactly the kind of ramp between the bogies mentioned above. On-board gap fillers are so standard at this point that curved platforms really shouldn't be an issue either.

(Stadler is the only manufacturer using them in the UK currently, but that's not for any reason other than their competitors just can't be bothered, they have all offered them for decades on the continent).

 

[Nottingham59]

I'm fairly certain you can get level boarding at 915mm for a high speed train without needing to majorly compromise on bogies. The Stadler SMILE platform is designed for 250km/h with level boarding at 780mm, for example.

Thanks for that. I know there's a technical or regulatory restriction on trains over 250km/h, so that speed is becoming a bit of a standard in Europe. Personally, I would say that 250km/h would have been quite adequate for HS2, but that's just my opinion.

Are there any 300-plus km/h trains out there with level boarding below 1115mm?

 

[Trainbike46]

Maybe in each driving car, so there's one at each end of unit?

The NS DDNG, while not high speed, will have level boarding in the end coaches only, so they followed this approach

Don't some of the Double Decker TGVs offer level boarding at 550mm platforms?

EDIT: it appears at least some do:

 

[Nottingham59]

Don't some of the Double Decker TGVs offer level boarding at 550mm platforms?

Yes, all the ones I've seen do. But they have flat access at the upper level from one end of the train to the other, which obviously wouldn't be practical on the GB classic network.

And the lower wells do feel very constrained and dark.

== Doublepost prevention - post automatically merged: 4 Sep 2024 ==

I see the Talgo 350 (330 km/h) has a flat floor at 760mm above the rail. They seem to have done this by putting the traction at each end. Does anyone know any more about these?

Design, Acquisition and Maintenance of the Rolling Stock - El tren del desierto

One factor that weighed heavily in the choice of the Al Shoula proposal is the international fame of the Spanish train fleet, its low carbon dioxide emissions

www.eltrendeldesierto.com

 

[JamesT]

Presumably the carriages with level boarding aren't motored? I believe HS2 were quite keen on distributed traction.

 

[MarkyT]

I see the Talgo 350 (330 km/h) has a flat floor at 760mm above the rail. They seem to have done this by putting the traction at each end. Does anyone know any more about these?

They have end power cars like previous high speed Talgo trains. The intercar walkway at ~760mm can pass between the tops of the independent wheels of the single-wheelset articulated 'bogie' at each unpowered passenger car coupling. Clearly, if they can manage 760mm (and they claim they can also do 550mm) Talgo could also do 915mm in a custom bodyshell design that would be necessary anyway for UK loading gauge. Unfortunately for first customer RENFE and Talgo, the latest Avril trains have been disappointing from a ride and reliability perspective so far.

I expect Alstom could also make a 360km/h level boarding high speed train for the UK using their Avelia platform power cars sandwiching a brand new articulated trailer set design achieving full level floor and level boarding at ~915mm. They could have powered gap filler steps using sensors to reach out to any location-specific horizontal platform offset, even on curves. However, this would conflict with HS2's requirement for distributed traction.

 

[signed]

The NS DDNG, while not high speed, will have level boarding in the end coaches only, so they followed this approach

Don't some of the Double Decker TGVs offer level boarding at 550mm platforms?

The new ones do at most stations, but I would say it's probably easier to do on TGV, since it's a Jacobs bogied (like a FLIRT) Loco-Hauled stock

With a loco-hauled, you don't have to carry traction motors, and with the Jacobs Bogie, you have a lot more room to go as low as needed

== Doublepost prevention - post automatically merged: 4 Sep 2024 ==

However, this would conflict with HS2's requirement for distributed traction.

The Avelia platform can do distributed traction (like on the Liberty), now would it fit on 915mm I don't know

 

[MarkyT]

The Avelia platform can do distributed traction (like on the Liberty), now would it fit on 915mm I don't know

Although Alstom hasn't ruled out AGV-style distributed traction for a particular customer solution, neither SNCF nor Amtrak (the only buyers so far) have taken that option yet. The Liberty has the similar end power cars to TGV-M with a custom tilting trailer set between them designed for US East Coast high platforms, around 1200mm.

 

[signed]

Amtrak (the only buyers so far) have taken that option yet

I thought they did, I stand corrected

 

[Trainbike46]

Presumably the carriages with level boarding aren't motored? I believe HS2 were quite keen on distributed traction.

The double-decker TGVs have power cars at the ends.

The wheel arrangement of the Stadler SMILE is 2′(Bo)′(Bo)′(2)′(2)′(2)′(2)′(Bo)′(Bo)′(2)′(2)′2'
All carriages have level boarding, including the ones that have motored bogies

The new ones do at most stations, but I would say it's probably easier to do on TGV, since it's a Jacobs bogied (like a FLIRT) Loco-Hauled stock

With a loco-hauled, you don't have to carry traction motors, and with the Jacobs Bogie, you have a lot more room to go as low as needed

Of course, there is no reason a UK high speed train couldn't have jacobs bogies where that offers design advantages

 

[MarkyT]

The Avelia platform can do distributed traction..., now would it fit on 915mm I don't know

Difficult to do without ramps over power bogies as conventional motors and gear trains are bulky and mounted between the wheels, and if all bogies are powered, there are a lot of ramps! That's why short FLIRTs only have them under the cabs and equipment areas immediately behind where the floor can be higher without affecting the walkthrough passenger accommodation. If manufacturers could devise more compact drives, maybe locating the motor under the adjacent car body and coupling via a cardan shaft like voyagers, or on the bogie but vertically aligned to the side between the car bodies then perhaps some space could be created. These are very high-performance drives on HS trains however so reengineering them smaller while maintaining safety and reliability is a major challenge. Shinkansen can fully distribute because they have universal high floors of around 1200mm, clear of conventional power bogies, and high platforms to match for level boarding. China copied that approach, eminently practical for new construction. That is what HS2 followed, despite the inevitable consequences at the classic network stations to be served. The new gen of low floor HS trains is still not yet fully nascent nor proven in service. Until VERY recently many manufacturers generally only offered high floor in their established distributed drive products such as AGV and Velaro. In all honesty, I can't fault HS2 at the time the initial decision was made. If the decision was being made anew today it might be different. We may have to accept high floors and steps for a long time at classic stations but from a safety and boarding speed perspective it's less of a headache with long-distance limited stop services, though it's still an inconvenience and risk for the less abled and more encumbered. At least on a prestige express service it will likely be justified to keep the platforms properly staffed for assistance, though mistakes can occur as demonstrated at Kings Cross recently. I expect development work on the trains is now at an advanced stage and probably too late to revise any specs beyond perhaps set makeup, I think it would be prudent to engineer the platforms at new HS2 stations to be convertible from an initial ~1200mm to 915mm for a future lower floor fleet.

 

[Nottingham59]

I think it would be prudent to engineer the platforms at new HS2 stations to be convertible from an initial ~1200mm to 915mm for a future lower floor fleet.

I think that's a really sensible suggestion. Or even just leave 30cm empty space above the loading gauge envelope to allow the track to be raised.

 

[renegademaster]

In every thread about crossrail , the non standard platform height always gets brought up , and people argue that it should have level boarding like the flirts.
However the flirts have a bumpy floor, which wouldnt be suitable for a metro style layout like the elizabeth line has. The metropolitan line manages , but with lower speed stock and smaller wheels. The question is can you do the same with 90mph trains?

 

[100andthirty]

Class 777 has level boarding, 75 mph top speed and ramps/humps over the articulated bogies as an indication of how hard it is to achieve platform height floor at doorways and a level floor throughout.

 

[HSTEd]

In every thread about crossrail , the non standard platform height always gets brought up , and people argue that it should have level boarding like the flirts.
However the flirts have a bumpy floor, which wouldnt be suitable for a metro style layout like the elizabeth line has. The metropolitan line manages , but with lower speed stock and smaller wheels. The question is can you do the same with 90mph trains?

The Stadler SMILE has level boarding at EU platforms (ie. lower than UK ones) at speeds rated up to 250km/h.

The TGV Duplex has a floor only ~300mm above the railhead.
It does not appear that there are any hard restrictions on meeting UK platform heights with level boarding at any reasonable speed.

Systems like the AGV have traction motors entirely contained within the bogies and the power electronics can be mounted in any convenient volume on the train.
The platform height arguments employed by HS2 and others don't really seem particularly convincing any longer.

However the flirts have a bumpy floor, which wouldnt be suitable for a metro style layout like the elizabeth line has.

Such layouts are fairly regularly used on trams, however.

 

[Bletchleyite]

The Stadler SMILE has level boarding at EU platforms (ie. lower than UK ones) at speeds rated up to 250km/h.

Though it has internal ramps/steps.

The TGV Duplex has a floor only ~300mm above the railhead.

It achieves this by having articulated bogies with the passenger compartment dropped between them. I can't remember the internal layout but I think the bit at the end above the bogies where the floor would be higher is used for electrical kit.

The only high speed train I know of that is able to avoid this is Talgo, as the wheels are independent, a bit like the front of a bus, they don't need the floor lifting for an axle.

 

[Nottingham59]

The only high speed train I know of that is able to avoid this is Talgo, as the wheels are independent, a bit like the front of a bus, they don't need the floor lifting for an axle.

what diameter are the Talgo's wheels? Even without an axle, the full wheel diameter has to be accommodated

 

[stuu]

what diameter are the Talgo's wheels? Even without an axle, the full wheel diameter has to be accommodated

They have single wheels which sit between the cars rather than a bogie, and are known for riding very badly as a result

 

[HSTEd]

Difficult to do without ramps over power bogies as conventional motors and gear trains are bulky and mounted between the wheels, and if all bogies are powered, there are a lot of ramps! That's why short FLIRTs only have them under the cabs and equipment areas immediately behind where the floor can be higher without affecting the walkthrough passenger accommodation.

Powered AGV bogies have the traction motors entirely within the bogie structural frame.
They don't require clear space above them nor are they larger than the trailer bogies, so far as I can tell. Certainly the motor housings don't extend beyond the tops of the attached structural mounting components, let alone the wheels.

The power electronics can be positioned anywhere in the train that is convenient.

My own view is that this is an insanely narrow minded decision, that is unfortunately rather typical to HS2's approach throughout. Given the huge emphasis they put on classic compatible services as part of their argument to get money, its insane that they then decided to permanently cripple said services with a non-standard platform height.

 

[JamesT]

Powered AGV bogies have the traction motors entirely within the bogie structural frame.
They don't require clear space above them nor are they larger than the trailer bogies, so far as I can tell. Certainly the motor housings don't extend beyond the tops of the attached structural mounting components, let alone the wheels.

The power electronics can be positioned anywhere in the train that is convenient.

My own view is that this is an insanely narrow minded decision, that is unfortunately rather typical to HS2's approach throughout. Given the huge emphasis they put on classic compatible services as part of their argument to get money, its insane that they then decided to permanently cripple said services with a non-standard platform height.

This article on the AGV https://www.railwaygazette.com/in-depth/wraps-come-off-the-agv/32721.article mentions:

A walk-through also reveals that the floor is almost level, rising from 1 155 mm above rail top in the saloon to just 1 250 mm over the bogie.

So the powered bogies may well be no bigger than the trailer variants, but the design still needs to get over them rather than walking through between the wheels.

 

[HSTEd]

This article on the AGV https://www.railwaygazette.com/in-depth/wraps-come-off-the-agv/32721.article mentions:

So the powered bogies may well be no bigger than the trailer variants, but the design still needs to get over them rather than walking through between the wheels.

Is 915mm to 1250mm truly unacceptable?
I'd argue either a ramp or step at the end of the carriage still leaves a far superior solution to what we've ended up with, which is steps at the door forever.

 

[MarkyT]

Is 915mm to 1250mm truly unacceptable?
I'd argue either a ramp or step at the end of the carriage still leaves a far superior solution to what we've ended up with, which is steps at the door forever.

I agree, but specifications required a level floor throughout the train. Perhaps, with retrospect, some steps or ramps internally would have been better than big steps at all doors at most stations served, for safe and efficient boarding with much lower risk of minor incidents at the interface and consequent disruption.

 

[AM9]

I agree, but specifications required a level floor throughout the train. Perhaps, with retrospect, some steps or ramps internally would have been better than big steps at all doors at most stations served, for safe and efficient boarding with much lower risk of minor incidents at the interface and consequent disruption.

Probably the number of passengers making the step across the train-platform interface is more relevant than a simple count of platforms with level boarding vs without.

 

[dosxuk]

Does anybody have accurate drawings of the relevant areas of the loading gauge? Needs to be accurate enough to draw the 915mm / 1100mm (XR) / 1115mm (HS2) "standards" on top.

 

[MarkyT]

Probably the number of passengers making the step across the train-platform interface is more relevant than a simple count of platforms with level boarding vs without.

With the current strategy, the limited number of new stations will still be Level Boarding, but the increase in classic platforms served elsewhere means some very popular destinations such as Manchester might be stuck with stepped boarding for decades. A 915mm-matching rolling stock solution, together with lowered platforms at the new stations could have provided LB everywhere immediately on opening. Mainland Europe is facing similar problems matching even lower platforms, especially in the HS sector, but solutions are beginning to emerge. E.g Talgo sets such as the Avila for Spain and new loco hauled IC sets for Germany, and Siemens new gen Railjets for Austria. The last example has more internal level changes than the Talgos, but the conventional bogies may result in a better ride.

 

[HSTEd]

Probably the number of passengers making the step across the train-platform interface is more relevant than a simple count of platforms with level boarding vs without.

Well, given the failure of the HS2 programme, it seems a very large fraction of passengers will have to deal with a step, forever.

This whole thing just seems to be another example of hubris.
What they decided makes sense if they assume that the entire programme will suceed and cannot fail, but otherwise it was a huge unnecessary risk.