backward APT train idea

[whuppy2025]

so this is my idea! you know about the Advanced Passenger Train (APT)? I have an idea to do the same thing, but backwards. if engineered right, you could fix the tilting problem with the APT and just tilt the train tracks instead. if engineered correctly, it would not make passengers inside sick, and slower trains could tilt so that the passengers inside are comfortable and don't feel the tilting tracks. and if engineered right, a train could travel at high speeds, pulling cities and towns closer together. I don't know if you guys will consider it or if it’s a good idea that can be done.

I sent this to national rail so it might sound like I'm trying to talk to them

 

[Bletchleyite]

That is already done, it's called "cant". It's quite visible somewhere like Berkhamsted on the WCML.

 

[zwk500]

This is what is already done with a thing called cant or superelevation. See: https://en.wikipedia.org/wiki/Cant_(road_and_rail)

It's the same concept as corner 'banking' used on racetracks.

If you're on a train that's unexpectedly held at a signal it can be quite noticeable. Lines such as the ECML and WCML make extensive use of it.

 

[whuppy2025]

That is already done, it's called "cant". It's quite visible somewhere like Berkhamsted on the WCML.

thank you for informing me

== Doublepost prevention - post automatically merged: 30 Oct 2025 ==

That is already done, it's called "cant". It's quite visible somewhere like Berkhamsted on the WCML.

thank you for telling me, they should do this in the uk

== Doublepost prevention - post automatically merged: 30 Oct 2025 ==

This is what is already done with a thing called cant or superelevation. See: https://en.wikipedia.org/wiki/Cant_(road_and_rail)

It's the same concept as corner 'banking' used on racetracks.

If you're on a train that's unexpectedly held at a signal it can be quite noticeable. Lines such as the ECML and WCML make extensive use of it.

thank you for telling me. very helpfull

 

[sad1e]

so this is my idea! you know about the Advanced Passenger Train (APT)? I have an idea to do the same thing, but backwards. if engineered right, you could fix the tilting problem with the APT and just tilt the train tracks instead.

BR tried this during the APT project and the issue you run into is that if you cant track at too large an angle you run into issues with slower freight traffic using the same lines as fast InterCity trains as slower freight trains don't benefit from can't in the track as it offsets their load and could potentially make them unstable.

Canting is done to a degree on most lines in the country but due to having to consider freight it cannot be done to a degree that cuts down on journey times as much as a tilting train would.

 

[whuppy2025]

That is already done, it's called "cant". It's quite visible somewhere like Berkhamsted on the WCML.

does "cant" have slower trains tilting on a cant curve that they don't feel the tilt inside?

== Doublepost prevention - post automatically merged: 30 Oct 2025 ==

BR tried this during the APT project and the issue you run into is that if you cant track at too large an angle you run into issues with slower freight traffic using the same lines as fast InterCity trains as slower freight trains don't benefit from can't in the track as it offsets their load and could potentially make them unstable.

Canting is done to a degree on most lines in the country but due to having to consider freight it cannot be done to a degree that cuts down on journey times as much as a tilting train would.

maybe slower trains could tilt at tilted corners so that whatever inside is not offset by an angle

 

[sad1e]

does "cant" have slower trains tilting on a cant curve that they don't feel the tilt inside.

Nope , being on canted track is very obvious when you're inside most rolling stock.

It's even more obvious on tilting stock as they tilt into the cant to allow for higher speeds.

 

[whuppy2025]

I am highly grateful for the attention this is getting

== Doublepost prevention - post automatically merged: 30 Oct 2025 ==

Nope , being on canted track is very obvious when you're inside most rolling stock.

It's even more obvious on tilting stock as they tilt into the cant to allow for higher speeds.

that makes sense

 

[DelW]

Many years ago I was on a Eurostar train that came to a halt on a sharp curve near Lille. We had a good sample of Eurostar's (then) free refreshments on the table, and we had to grab hold of all the bottles and glasses before they slid off onto the floor. The slope (= cant) felt really steep!

 

[whuppy2025]

Many years ago I was on a Eurostar train that came to a halt on a sharp curve near Lille. We had a good sample of Eurostar's (then) free refreshments on the table, and we had to grab hold of all the bottles and glasses before they slid off onto the floor. The slope (= cant) felt really steep!

very nice

 

[zwk500]

thank you for telling me, they should do this in the uk

There is a curve with between 42 and 125mm of Cant Approximately half a mile past where the single line out of Penzance transitions to double track. The most extreme section is just east of the road bridge over the railway at Marazion.
The approach to Doncaster from the South has 154mm of Cant (which I have felt at a stand when held at a red, it was very noticeable, thankfully I was on the inside so just leant into the wall).

Others on here may know the maximum acceptable values on the network.

(Values are from the 5 Mile Diagrams, so I may have misread them - open to correction!)

 

[The exile]

Another issue is of course that canting track will affect where the rest of the train sits within the envelope of the loading gauge. It's extremely unlikely that canting track (and therefore tilting the sides of the train away from the vertical) would result in a train actually hitting anything like the side of a bridge - but it could easily result in the top of the train (where the effect will be the greatest) getting too close to structures to be safe (in other words the train getting "out of gauge")

 

[whuppy2025]

Another issue is of course that canting track will affect where the rest of the train sits within the envelope of the loading gauge. It's extremely unlikely that canting track (and therefore tilting the sides of the train away from the vertical) would result in a train actually hitting anything like the side of a bridge - but it could easily result in the top of the train (where the effect will be the greatest) getting too close to structures to be safe (in other words the train getting "out of gauge")

how could you fix those problems tho?

 

[zwk500]

how could you fix those problems tho?

3 primary ways - rebuild the structures, reduce the speed so reduce the cant, or accept a 'cant deficiency' which is the difference from the ideal cant for the intended speed. Cant deficiency causes issues with wear and tear and passengers feeling the forces more, but can be quite useful in avoiding short areas of specific speed restrictions.

If you are very lucky you may have room to realign the tracks to avoid the bridges.

 

[43096]

thank you for telling me, they should do this in the uk

Berkhamsted (as the example given) is the UK!

 

[edwin_m]

Cant deficiency causes issues with wear and tear and passengers feeling the forces more, but can be quite useful in avoiding short areas of specific speed restrictions.

It's normally the case that a train rounding a curve at full line speed will have some degree of cant deficiency, as (to vastly oversimplify the job of track engineers) the cant is chosen to as a compromise between wear on the outer rail from fast trains and wear on the inner rail from slow ones.

Which brings us back to the APT, which tilted the body inwards on curves (as Pendolinos still do) to reduce the cant deficiency felt by the passengers. The train itself is still running at a higher cant deficiency than normal, so the outer rail will wear more, but for there to be any risk of overturning it would have to run much faster than passengers could tolerate even in a tilting train.

 

[SynthD]

Can the tilting trains tilt the other way if they are stationary on top of cant and the driver chooses to make the passengers more level? Or is it balise-based with no driver input?

 

[sad1e]

Can the tilting trains tilt the other way if they are stationary on top of cant and the driver chooses to make the passengers more level? Or is it balise-based with no driver input?

On stock such as 390's and 221's the tilt is all balise based. No idea on the APT though.

 

[edwin_m]

Can the tilting trains tilt the other way if they are stationary on top of cant and the driver chooses to make the passengers more level? Or is it balise-based with no driver input?

I believe the APT could do this, at least originally, as the tilting was driven by a control system that aimed to cancel out any lateral acceleration within the coach body. The tilt was however changed at least once, including to only partially compensate lateral accelerations as this reduced passenger travel sickness, so this feature may have been discontinued. I think the Pendolino tilt works by sensing the rotation of the bogies, so wouldn't tilt the wrong way. I don't believe either had or has a facility for the driver to control the amount of tilt, other than by isolating the entire tilt system.

 

[whuppy2025]

Berkhamsted (as the example given) is the UK!

then they should do it everywhere in the UK

 

[43096]

then they should do it everywhere in the UK

It is used widely in the UK.

 

[zwk500]

then they should do it everywhere in the UK

As has been mentioned with the example of Penzance, they do.

 

[MarkyT]

On stock such as 390's and 221's the tilt is all balise based. No idea on the APT though.

They had a system called C-APT which used passive track transponders very similar to later balises. It was less sophisticated that modern TASS, relying on drivers simply acknowledging an upcoming speed reduction like AWS to avoid a brake intervention.

Control - Advanced Passenger Trains (C-APT)

Control - Advanced Passenger Trains
Driver Aid System (C-APT)
...
A continuous cab display of the maximum permitted APT speeds on sections of track is given by the control system based on transponders, measuring 19" × 36" × 2", mounted on the track at specific intervals.

 

[whuppy2025]

They had a system called C-APT which used passive track transponders very similar to later balises. It was less sophisticated that modern TASS, relying on drivers simply acknowledging an upcoming speed reduction like AWS to avoid a brake intervention.

Control - Advanced Passenger Trains (C-APT)

thank you