How fast can high speed trains actually go?

[Sad Sprinter]

What’s the highest speed we can currently build trains to run at in normal service? And how much upgrades will it take for existing high speed lines to handle faster trains?

 

[ExRes]

I can't imagine there will be any increase whatsoever on the current 125mph, where is the money going to come from to rebuild lines for the minimal time benefit any increase would give? in my opinion there's far too much that needs to be done elsewhere in the industry to waste money on saving a couple of minutes here and there

 

[AM9]

What’s the highest speed we can currently build trains to run at in normal service? And how much upgrades will it take for existing high speed lines to handle faster trains?

HS2 is designed for a maximum speed of 400km/h, so it is reasonable to assume that such trains could be designed fairly early in the route's life (as a part of 120 years).

 

[Sad Sprinter]

HS2 is designed for a maximum speed of 400km/h, so it is reasonable to assume that such trains could be designed fairly early in the route's life (as a part of 120 years).

What’s 400 kph in miles?

Can trains go even faster than that?

 

[AM9]

What’s 400 kph in miles?

Can trains go even faster than that?

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.

 

[Sad Sprinter]

Interesting so call it 250. I wonder how you can get a 400m long train run in normal service at 300mph. Possibly with power cars and powered axels under the coaches.

 

[Peter Mugridge]

The current generation of TGVs, and the LGVs they run on, are capable of 320 km/h ( 200mph ) in normal service but will usually run at 300 km/h ( 186 mph ) as they are mixed in with older versions of TGV that are only able to use that speed.


Glossary:

TGV: Train Grande Vitesse

LGV: Ligne Grande Vitesse

 

[Sad Sprinter]

The current generation of TGVs, and the LGVs they run on, are capable of 320 km/h ( 200mph ) in normal service but will usually run at 300 km/h ( 186 mph ) as they are mixed in with older versions of TGV that are only able to use that speed.


Glossary:

TGV: Train Grande Vitesse

LGV: Ligne Grande Vitesse

I was wondering if LGV nord and South East could be upgraded to higher line speed (250+) and if that would improve the business case for more international high speed traffic, or whether new, even faster lines would be necessary. I know which option I’d pick!

 

[Peter Mugridge]

I was wondering if LGV nord and South East could be upgraded to higher line speed (250+) and if that would improve the business case for more international high speed traffic, or whether new, even faster lines would be necessary. I know which option I’d pick!

Depends on the curve radius really, but they are mostly fairly straight so it should be possible - but of course you'd need all the rolling stock to be capable of the speed as well otherwise you'll lose capacity from the different performance profiles tripping over each other, as happens on the main lines in the UK at the moment.

You'd need to beware of "bunching" at the places where there are tighter curves, such as around Lille. That could also hit capacity.

 

[PGAT]

Do Maglevs count? If so, then Japan got up to 603kph (375mph) and the test trains are intended for 500kph (311mph) in regular service

 

[43096]

The current generation of TGVs, and the LGVs they run on, are capable of 320 km/h ( 200mph ) in normal service but will usually run at 300 km/h ( 186 mph ) as they are mixed in with older versions of TGV that are only able to use that speed.


Glossary:

TGV: Train Grande Vitesse

LGV: Ligne Grande Vitesse

That depends which LGV route they are on. LGV Est is 320km/h and trains get to that speed - the time I did it, it was actually a DB ICE set.

 

[MarkyT]

Depends on the curve radius really, but they are mostly fairly straight so it should be possible - but of course you'd need all the rolling stock to be capable of the speed as well otherwise you'll lose capacity from the different performance profiles tripping over each other, as happens on the main lines in the UK at the moment.

You'd need to beware of "bunching" at the places where there are tighter curves, such as around Lille. That could also hit capacity.

Japanese Shinkansen operators have adopted a small degree of tilt capability on the N700 rolling stock from 2007 to increase speed marginally to 270kph on the quite sinuous original Tōkaidō high-speed line from the 1960s, which has numerous 2500m radius curves. This saved 8 minutes on the fastest Tokyo-Osaka runs compared to previous rolling stock. The N700 and latest N700S can go faster than this, up to 300kph, on other parts of the network, where not so constrained by curvature.

The 400kph design speed of HS2 incorporates sensible headroom for future developments, even if initial rolling stock cannot exceed 350kph. Brunel no doubt knew from calculations that his generous GWML curves of the 1840s could support speeds greater than that physically possible with the locos and rolling stock of the time.

 

[Sorcerer]

In theory you can certainly push a high-speed train above 400km/h (250mph) since the TVM signalling system is built for 430km/h (270mph) capability. The Frecciarossa trains in Italy are built with a design speed of 400, and it could be possible that future HS2 stock of the same family will be built with those speeds in mind. The fastest speed record for wheeled trains is 574km/h (357mph) with a TGV that used technology later incorporated into the AGV that has a top design speed of 360km/h (225mph). In reality though conventional trains operating at such speeds in regular revenue service would end up being more costly than beneficial due to the need for greater spacing between trains and distances between signals which would end up reducing capacity, which is crucial in the age of a climate crisis where you want more people on high-speed trains as an alternative to domestic flights and long-distance car travel. Not to mention the increased building and maintenance costs for both the track and trains themselves.

 

[The Planner]

Also factor in the amount of power they would drink getting to and maintaining such speeds as well as how long you can actually keep them at that speed for.

 

[MarkyT]

Also factor in the amount of power they would drink getting to and maintaining such speeds as well as how long you can actually keep them at that speed for.

It's a complicated set of calculations with a lot of inputs. Faster trains need better crashworthiness and that often adds weight. Unless the sustained running at the higher speed thus enabled is far enough, a decrease in weight to allow better acceleration to, and later braking from, a lower top speed might be able to equal overall point-to-point section times. Much of the effort in refining the latest trains has concentrated on weight-saving and aerodynamics. The latest Velarios and Avelias have air-smoothed fairings over everything to reduce turbulence and thus air resistance, leading to improved energy economy.

 

[HSTEd]

It's a complicated set of calculations with a lot of inputs. Faster trains need better crashworthiness and that often adds weight.

Once you climb above 300km/h crashworthiness is only of limited usefulness.

If the train hits something at 400km/h or more its almost impossible to engineer the survival of the passengers.

 

[The exile]

In many ways it’s less of a question of “how fast they can go” than if “how long do they take to stop?” - without decanting passengers and luggage to the floor.

 

[AM9]

In many ways it’s less of a question of “how fast they can go” than if “how long do they take to stop?” - without decanting passengers and luggage to the floor.

... and of course, just how much business would shaving 2.5 seconds per km bring against the 350km/h to 400km/h step increase in operational, maintenance initial capital cost of acheving those speeds. Bear in mind that such a time saving is only achieved whee the trains actually can reach those speeds, after acceleration and before braking.

 

[SynthD]

Once you climb above 300km/h crashworthiness is only of limited usefulness.

If the train hits something at 400km/h or more it’s almost impossible to engineer the survival of the passengers.

Who said this?

 

[Dan G]

I've always wondered if HS2 would have been cheaper if built for an entirely adequate 300 kph instead of 400. Four hundred smelt of willy-waving to me. If France are content with 300-320 kph, we should be too.

 

[Norm_D_Ploom]

I've always wondered if HS2 would have been cheaper if built for an entirely adequate 300 kph instead of 400. Four hundred smelt of willy-waving to me. If France are content with 300-320 kph, we should be too.

Correct. Given that the reason for building was capacity not speed it would have been a much better sell.
Most of the ICE network is 280k, that would have been more than adequate and considerably cheaper.

 

[Energy]

I've always wondered if HS2 would have been cheaper if built for an entirely adequate 300 kph instead of 400. Four hundred smelt of willy-waving to me. If France are content with 300-320 kph, we should be too.

HS2 spent a while talking to other European countries and one if the recommendations was to overbuild on speed

 

[AM9]

Correct. Given that the reason for building was capacity not speed it would have been a much better sell.
Most of the ICE network is 280k, that would have been more than adequate and considerably cheaper.

In the next few years it is likely that many of the 70mph limits on non-motorway roads will be lowered to 60mph or even 50mph. So why not build new roads (especially bypasses) or any revised junctions to specification for a 50mph speed limit? Also make single carriagway roads 50mph or even 40 mph? Both would be considerably cheaper, reduce traffic noise/vibration, reduce KSI incidents and lower energy consumed.
It's all part of the same equation, why should either be built on lines that don't acknowledge likely future trends?

 

[SynthD]

The route would be longer as it winds more to use cheaper land. But it wouldn’t be cheaper in urban areas as the turning radius for 300kph is still huge. In turn, you’d receive less benefit, less change away from motorways and airports, less relief on the classic lines, less freight movements there. What’s not willy waving about 300?

 

[hexagon789]

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.

 

[snowball]

The route would be longer as it winds more to use cheaper land. But it wouldn’t be cheaper in urban areas as the turning radius for 300kph is still huge. In turn, you’d receive less benefit, less change away from motorways and airports, less relief on the classic lines, less freight movements there. What’s not willy waving about 300?

Tighter curves could mean a shorter route in some cases. A long curve could be replaced by two tighter curves connected by a straight. It could also make it easier for a line to run alongside an existing motorway.

 

[SynthD]

It could also make it easier for a line to run alongside an existing motorway.

Is that an unrealistic dream that won't die?

 

[Grumpy Git]

I've always wondered if HS2 would have been cheaper if built for an entirely adequate 300 kph instead of 400. Four hundred smelt of willy-waving to me. If France are content with 300-320 kph, we should be too.

Nail on head. No doubt decided by someone with zero engineering skills.

 

[AM9]

Tighter curves could mean a shorter route in some cases. A long curve could be replaced by two tighter curves connected by a straight. It could also make it easier for a line to run alongside an existing motorway.

The difference is negligible. I can't find the definitive minimum radius for HS2 but figures from European HS lines talk about 7000m radius for 400 km/h and 6000m for 350 km/h, (the exact realtionship depends on vehicle designs and a 400 km'h design woud have dynamics appropriate to the line quality). So in terms of longer or shorter routes and assuming those figures, a 20 deg deviation would be a 2.4km curve on a 400km/hour alignment, whereas the curved part(s) of the same deviation would be about 2.09km plus the associated straight(s) would be no more than 30m less which is neglible from a cost point of view and less than a second in travelling time

 

[snowball]

Is that an unrealistic dream that won't die?

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.