How fast can high speed trains actually go?

[Sad Sprinter]

The French may run at only 300-320 in service, but the 320 lines were deliberately designed for 350 running as a measure of 'future-proofing'.

Surely the same applies here?

It is not beyond imagination to forsee trains running routinely at 360km/h in the future.

The French reputedly regret the limitations of the original LGV Sud-Est, as while it was upgraded to 300km/h running, the tighter radius curves compared to subsequent lines, impose a number of 270km/h restrictions for curvature, hampering efficiency and eating some capacity.

Aren’t they building a new line anyway to Lyon via Orleans?

 

[hexagon789]

Aren’t they building a new line anyway to Lyon via Orleans?

I know it's been a plan since Sarkozy was still President, but whether it has progressed beyond an aspiration...

 

[AM9]

The proposed route for the HS2 eastern arm included substantial stretches more or less alongside the M42, A42, M1 and M18, but with narrow strips of land in between where the road was too curvy. If tighter radii had been adopted for the railway, those would have been narrower.

But the formation would have been (slightly) more expensive to make with higher stresses in service with an even more useless bit of land in between.

 

[mike57]

There will be a physical limit where the torque at wheel required to accelerate the train will be greater than the wheel - rail friction, taking into account all the resistances, wind, gradient etc. On level or nearly level track I have no idea when that might begin to be the limiting factor.

The power required will be another issue, there must be a limit with the current 25kV system.

Heating of the nose area due to air friction might also be an issue.

Listening to the accounts of the record breaking TGV ~350mph I get the feeling they were pretty close to the limits of the current technology.

Its also interesting that the Chinese high speed rail was originally planned I think to run at 350kph and did for a few years on a few routes, but I think in most cases they settled back to 300-320kph.

All this points 300-320kph, around 200mph being a sensible maximum speed with current technology. I also wondered why we went for 400kph, if we had the distances the Chinese do then maybe, but its interesting that for the moment they seem content with 200mph/320kph. How much time would be saved beween London and Birmingham at 300 v 400kph, allowing for accelaration and braking, and sections with a lower line speed

 

[JamesT]

There will be a physical limit where the torque at wheel required to accelerate the train will be greater than the wheel - rail friction, taking into account all the resistances, wind, gradient etc. On level or nearly level track I have no idea when that might begin to be the limiting factor.

The power required will be another issue, there must be a limit with the current 25kV system.

Heating of the nose area due to air friction might also be an issue.

Listening to the accounts of the record breaking TGV ~350mph I get the feeling they were pretty close to the limits of the current technology.

Its also interesting that the Chinese high speed rail was originally planned I think to run at 350kph and did for a few years on a few routes, but I think in most cases they settled back to 300-320kph.

All this points 300-320kph, around 200mph being a sensible maximum speed with current technology. I also wondered why we went for 400kph, if we had the distances the Chinese do then maybe, but its interesting that for the moment they seem content with 200mph/320kph. How much time would be saved beween London and Birmingham at 300 v 400kph, allowing for accelaration and braking, and sections with a lower line speed

My understanding is that the initial rolling stock is specified for 360kph maximum, with services scheduled at 320kph.
But the formation is being built for 400kph, as you only get to build that once.

 

[InkyScrolls]

That is 248mph, but the world speed record for a standard gauge train is held by the French on a very specially prepared train, - 574.78km/h (352.7mph in obsolescent imperial measurement). That speed is far from repeatable at present.

Far from obsolescent. The majority of the public use both Imperial and metric, as I'm sure you are aware.

 

[Sad Sprinter]

There will be a physical limit where the torque at wheel required to accelerate the train will be greater than the wheel - rail friction, taking into account all the resistances, wind, gradient etc. On level or nearly level track I have no idea when that might begin to be the limiting factor.

The power required will be another issue, there must be a limit with the current 25kV system.

Heating of the nose area due to air friction might also be an issue.

Listening to the accounts of the record breaking TGV ~350mph I get the feeling they were pretty close to the limits of the current technology.

Its also interesting that the Chinese high speed rail was originally planned I think to run at 350kph and did for a few years on a few routes, but I think in most cases they settled back to 300-320kph.

All this points 300-320kph, around 200mph being a sensible maximum speed with current technology. I also wondered why we went for 400kph, if we had the distances the Chinese do then maybe, but its interesting that for the moment they seem content with 200mph/320kph. How much time would be saved beween London and Birmingham at 300 v 400kph, allowing for accelaration and braking, and sections with a lower line speed

I suppose 250mph makes sense on non stop runs on a full high speed line to Glasgow.

I wonder if maglev technology will be what we replace high speed lines with in 50 years or so, especially on longer international trips

 

[Energy]

My understanding is that the initial rolling stock is specified for 360kph maximum, with services scheduled at 320kph.
But the formation is being built for 400kph, as you only get to build that once.

The SNCF V360 OHLE used on HS2 is only rated for 360kph anyway

 

[AM9]

Far from obsolescent. The majority of the public use both Imperial and metric, as I'm sure you are aware.

We have been a metric country since the 1960s, the fact that some people are still having problems with Km measurements is regrettable. Anyway to keep on topic, this thread about HS2 and as it is an entirely metric railway, Km/h is the appropriate term for designed linespeeds. Much of the classic railway now uses speeds in metric units anyway, as noted in a recent thread about the limiters on class 80x units being set to a round metric value instead of 201.169 Km/h.

 

[Shimbleshanks]

I suppose if we are talking about railed vehicles, the set-ups used by the US military for testing aircraft fuselages suggest that there is almost no limit to how fast you can go given enough power and distance. These use what is essentially a long, straight rail track with the fuselages being tested bolted to a sled that is prevented from leaving the rails by lugs that fit underneath the bulge at the top of the rail.
I think they held the land speed record for manned vehicles at one time and subsequent tests with unmanned sleds have pushed the speeds achieved into the thousands of mph, I believe. I think they had to stop doing manned tests because the G-forces in acceleration and deceleration would have been fatal.

 

[mike57]

the set-ups used by the US military for testing aircraft fuselages suggest that there is almost no limit to how fast you can go

I was thinking more of wheel driven, steel wheel on steel rail in terms of a physical limit, as there will come a point where the torque required is greater than can handled by the rail wheel interface.

 

[Sorcerer]

How much time would be saved beween London and Birmingham at 300 v 400kph, allowing for accelaration and braking, and sections with a lower line speed

HS2 website claims the Phase One route is about 140 miles (that's 225 kilometres). So putting that in a speed distance time calculation you get 45 minutes for 300km/h and 33 minutes 45 seconds for 400km/h which is a time save of about 11-12 minutes. However, this likely does not account for the necessary acceleration and deceleration required to reach and come down from such a a speed, therefore the difference on a such relatively short route is practically negligible. Even at 360km/h the time calculation is just 37 minutes (an 8 minute saving from 300km/h) while 320km/h is 42 minutes (a 3 minute saving). It's only really on routes like London-Glasgow where you'd see a big difference in time saves between the 300-400km/h top speed (about 30 minutes).

 

[The Planner]

HS2 website claims the Phase One route is about 140 miles (that's 225 kilometres). So putting that in a speed distance time calculation you get 45 minutes for 300km/h and 33 minutes 45 seconds for 400km/h which is a time save of about 11-12 minutes. However, this likely does not account for the necessary acceleration and deceleration required to reach and come down from such a a speed, therefore the difference on a such relatively short route is practically negligible. Even at 360km/h the time calculation is just 37 minutes (an 8 minute saving from 300km/h) while 320km/h is 42 minutes (a 3 minute saving). It's only really on routes like London-Glasgow where you'd see a big difference in time saves between the 300-400km/h top speed (about 30 minutes).

And the fact its not the top speed for the whole distance. Once you get to Birmingham Interchange and Delta Jn it drops and it will drop at OOC as well. Its 11 odd miles from Interchange to Curzon St and 5 or so from OOC to Euston.

 

[MarkyT]

I was thinking more of wheel driven, steel wheel on steel rail in terms of a physical limit, as there will come a point where the torque required is greater than can handled by the rail wheel interface.

Conventional steel on steel trains might be propelled by linear motors mounted in the track or on the trains, as implemented on earlier lines of the Vancouver Skytrain in Canada. Assuming it could also be used at higher speeds, the technology could overcome adhesion limits to achieve maglev-like acceleration. It probably wouldn't change the upper speed limit steel wheels can achieve safely, economically and in comfort although separate refinements in suspension design, wheel and rail profile etc. have enabled speed to be increased progressively throughout modern railway history. That is likely to continue in the future which is why it was sensible to spec HS2 alignment design for 400kph. It's even possible top speed might be increased beyond that if a small degree of tilt could be incorporated in future train designs like the Japanese N700 series.

 

[Sad Sprinter]

We have been a metric country since the 1960s, the fact that some people are still having problems with Km measurements is regrettable. Anyway to keep on topic, this thread about HS2 and as it is an entirely metric railway, Km/h is the appropriate term for designed linespeeds. Much of the classic railway now uses speeds in metric units anyway, as noted in a recent thread about the limiters on class 80x units being set to a round metric value instead of 201.169 Km/h.

I don’t think we have been a metric country since the 60s. We clearly use a mixed system of both measurements. Miles was still the measurement used of speed and distance in railway magazines until I stopped buying them religiously 10 years ago.

 

[Energy]

I don’t think we have been a metric country since the 60s. We clearly use a mixed system of both measurements. Miles was still the measurement used of speed and distance in railway magazines until I stopped buying them religiously 10 years ago.

The country uses both but HS2 (and HS1) uses kph.

 

[AM9]

I don’t think we have been a metric country since the 60s. We clearly use a mixed system of both measurements. Miles was still the measurement used of speed and distance in railway magazines until I stopped buying them religiously 10 years ago.

We have been legally in a metric country since 1962, in 1978, it was necessary to pass legislation to force some parts of industry to implement statutes made in the 1960s. The only resistance to using metric measurement is in a small sector of the public. Road signs have continued to be in miles and mph, but we are talking about (rail)roads here where all new UK lines includung many metro railways, are fully metricated, and the part of the population stuck in imperial speed and distance measurement is irrelevant, - if they are driving trains then they for sure will know the difference!

 

[class26]

I don’t think we have been a metric country since the 60s. We clearly use a mixed system of both measurements. Miles was still the measurement used of speed and distance in railway magazines until I stopped buying them religiously 10 years ago.

We hven`t. I was at school in the last year to learn imperial and left school in 1972. Metric change might have been before then but I only learned in imperial

 

[AM9]

We hven`t. I was at school in the last year to learn imperial and left school in 1972. Metric change might have been before then but I only learned in imperial

Many industries were progressing with metrication by the end of the '60s, it was a small core of the lay public that were resistant to change (quelle surprise!) which scurrilous politicians used to patronise their indulgence. I left school in '65 with no formal schooling on metrics, but my comprehensive knowledge of counting in units, tens and hundreds from my primary schooldays saw me through.

 

[InkyScrolls]

We have been legally in a metric country since 1962, in 1978, it was necessary to pass legislation to force some parts of industry to implement statutes made in the 1960s. The only resistance to using metric measurement is in a small sector of the public. Road signs have continued to be in miles and mph, but we are talking about (rail)roads here where all new UK lines includung many metro railways, are fully metricated, and the part of the population stuck in imperial speed and distance measurement is irrelevant, - if they are driving trains then they for sure will know the difference!

And yet on the vast majority of the rail network, measurements are done in chains.

 

[snowball]

We hven`t. I was at school in the last year to learn imperial and left school in 1972. Metric change might have been before then but I only learned in imperial

At primary school (1954-1960) I was taught in both systems. A grammar school (1960-1967) I was taught in both systems but with science in metric only.

== Doublepost prevention - post automatically merged: 8 Sep 2023 ==

And yet on the vast majority of the rail network, measurements are done in chains.

I'm sure the designers of major civils such as HS2, Werrington underpass, Norton Bridge diversion use metric only. Train designers use metric only. New electrification structures are numbered in metric only these last 50 years.

 

[InkyScrolls]

I'm sure the designers of major civils such as HS2, Werrington underpass, Norton Bridge diversion use metric only. Train designers use metric only. New electrification structures are numbered in metric only these last 50 years.

All true - but that does not negate my point.

 

[coppercapped]

I don’t think we have been a metric country since the 60s.

Then you are wrong. The metric system of weights and measures became legal for use in the British Empire in 1896. The Imperial Units definitions of mass, length and volume used in the UK were re-defined in terms of metric units by the various Weights and Measures Acts of 1963 and 1985.

We clearly use a mixed system of both measurements. Miles was still the measurement used of speed and distance in railway magazines until I stopped buying them religiously 10 years ago.

Yes, this is true. But there are strict legal limits in the number of products which may be sold using Imperial units, for example draught beer, milk and some other products. Road speed limits are still quoted in miles per hour; this was not changed due to the potential confusion it could cause in the changeover period.

But the Ordnance Survey has used a metric grid for a hundred years...

At primary school (1954-1960) I was taught in both systems. A grammar school (1960-1967) I was taught in both systems but with science in metric only.

== Doublepost prevention - post automatically merged: 8 Sep 2023 ==

Yup, me too...! Except I was at grammar school a bit earlier (between 1955 and 1962) and all our teaching in arithmetic, chemistry and physics was in a 10-based system. We were even introduced to the differences between the cgs and the mks systems.[1] It was assumed that we understood Imperial Units...

...so we ran the 100 yards on Sports Day...!

I'm sure the designers of major civils such as HS2, Werrington underpass, Norton Bridge diversion use metric only. Train designers use metric only. New electrification structures are numbered in metric only these last 50 years.

Yes, definitely. Only in the US is stuff still designed using their equivalent of the Imperial System, but even that is fading. Some technical stuff in the US is changing to metric - already 30 years ago circuit board design used a metric grid.

[1] cgs: centimetre, gram, second. mks: metre, kilogram, second. The mks system morphed into the SI (Systéme International) system which is universally used today.

 

[AM9]

All true - but that does not negate my point.

Your 'point' is irrelevant to this discussion which is about 'High Speed' trains. The UIC, of which the UK has been an active member since its creation in 1922, defines HS rail as running at 200Km/h or more with various speed points going upwards from there. For the sake of those who can't/won't use Km/h, 200Km/h is given as 124m/h. So, this discussion is about speeds in the HS range on a rail;way that is part of the UIC so Km/h is the appropriate unit with which to define speeds. I doubt that the majority of the public knows what the speed limit on railway routes in the UK are, and nor shouldd it bother them, it's part of an engineering discussion. Even the US is moving into metric speed definition on its rail system as it orders much more equipment from global sources tha hitherto

 

[Irascible]

The limit is more economics than physics - I believe there's a practical ceiling of about 320kph, may be 350kph, more than that and energy costs get quite mad. There is a similar sort of barrier in a car, unsurprisingly.

 

[Shimbleshanks]

Could the fascinating discussion on metric versus imperial measurements go into its own thread?

 

[Sad Sprinter]

Could the fascinating discussion on metric versus imperial measurements go into its own thread?

Don’t bother, debating measurements is a dangerous recipe for a brexit debate