Trivia> 100mph+ to a stop. How far?

[Howardh]

Not counting emergency slam on the breaks, often wondered under dry conditions how far from a station a train going at or over 100mph would start to slow down.
Completely understand things like curves, gradients, crossings let alone the type/age of the train and brakes etc will affect this, but is there an actual (average) answer, such as which units would be the *slowest* to stop? What would be the biggest factor, the condition of the brakes?

Specifically, if a pendo is travelling at say 120mph, how much time is lost on breaking, stood at station and then accelerating back to 120 compared with if there was no stop?

 

[A-driver]

Not sure exact distances but if I'm doing 100mph on the down fast and stopping at Stevenage station I put the brake in around the point in which the mainline goes over the top of the down Hertford line, south of Langley junction. Roughly step 1 brake on a 365 and step1/2 on a 321/317. Looking at a map you may be able to work out the distances. That's a fairly flat gradient.

But as you sort of say, there is no set answer-all depends on type of stock and gradients.

Just looked at an OS Map and that's a distance of approximately 1.25 miles. Some drivers brake harder and closer to Langley junction which is just about a mile.

 

[HarleyDavidson]

Desiro? Depending on the railhead condition, 100-0 using 100% brake, probably ~¾ mile, you can go under the footbridge at Woking junction at 90 and stop quite comfortably in the platform, however I wouldn't try it in the autumn. It'll be less on a uphill gradient.

I know I can just about do the home signal to Milford on the up at 80 (falling gradient) and give it 100% and stop in the platform (8-car), I know that as I did it by accident a couple of years ago, when I thought I was fast Haslemere to Godalming!

 

[telstarbox]

If you know the top speed and are able to time the deceleration on the train, you can estimate the stopping distance as follows:

s = 0.5 * (u + v) * t [s is distance, u is initial speed, v is final speed, t is time]

The final speed is zero when the train stops, so it simplifies to:

s = 0.5 * v * t

Using A-driver's data above that suggests a braking period of about 90 seconds although in reality the deceleration will not be constant.

 

[HSTEd]

The Fastech 360Z test train in Japan was supposed to be able to stop from 360kph in under 4,000m.
But that was using fancy pop-out drag fins.
Best they could manage a 4,000m stopping distance without using them was only about 320kph.

 

[E50019]

Braking distance for a train travelling at 100mph on level track would be 2041m. (composite braking table)

For trains with enhanced brakes (ie modern traction) this distance is 1341m

Taken from the lineside signal spacing, railway group standard.

 

[Howardh]

It comes across as being quite a science!

 

[contrex]

It comes across as being quite a science!

It's called "physics".

 

[telstarbox]

Or GCSE Maths

 

[FordFocus]

Can vary with certain unit depending on brake pads, air pressures and other small things. Certain units I'm driving having a tendency to have a bit more air pressure in the B.C. e.g. Step 1 can be 1.75bar instead of 1.3-1.5 despite the units all been lightly loaded or unladen. So your usual braking point maybe too early and you have to release the brakes.

 

[edwin_m]

Braking distance for a train travelling at 100mph on level track would be 2041m. (composite braking table)

For trains with enhanced brakes (ie modern traction) this distance is 1341m

Taken from the lineside signal spacing, railway group standard.

Signal spacings are deliberately pessimistic so this is the distance the train must stop within and with good adhesion the actual stopping distance would be less.

Modern units are capable of service deceleration at 9% of gravity. Stopping distance works out at about 1100m if used continuously all the way down from 100mph, but no driver is actually going to do that!

 

[HarleyDavidson]

Really? I have done it into Winchester and phased the brake out to come to the perfect stop at the right mark in the past. Nowt wrong with doing it either.

Maybe not the most comfortable deceleration curve,but you can make up time doing it.

 

[edwin_m]

Really? I have done it into Winchester and phased the brake out to come to the perfect stop at the right mark in the past. Nowt wrong with doing it either.

Maybe not the most comfortable deceleration curve,but you can make up time doing it.

I assumed anyone who did that would be be done under "Professional" driving policies...

 

[FordFocus]

Some recent resignalling schemes have very optimistic signalling spacing between signals, if your having to put a train into full service there is a problem....

 

[HarleyDavidson]

I assumed anyone who did that would be be done under "Professional" driving policies...

No, why would they. The brake is there to be used and I'll use it the way I see fit and if it means that I have to use 100% brake then I will.

I use step 3 on 455 units quite a lot, because that's the way I was taught to use a 3 step brake. Those who write these so called "professional driving policies" quite often have never driven a train. :roll:

 

[edwin_m]

No, why would they. The brake is there to be used and I'll use it the way I see fit and if it means that I have to use 100% brake then I will.

I use step 3 on 455 units quite a lot, because that's the way I was taught to use a 3 step brake. Those who write these so called "professional driving policies" quite often have never driven a train. :roll:

I'm not saying you're wrong! Expecting drivers not to use maximum brake for stations at times of good adhesion is pretty pointless in my view, just slowing the journey for no safety benefit. Signals may be a different matter, and a policy of treating the two differently could actually improve safety.

 

[HarleyDavidson]

I only do it to make up (regain) lost time, last time I did it on 8 stations and with some deft handling made back 10 mins of 14 that were lost.

 

[FordFocus]

I don't plan to use step 3 in my normal braking technique but I have no fear in using as and when required.

 

[notadriver]

I'm not saying you're wrong! Expecting drivers not to use maximum brake for stations at times of good adhesion is pretty pointless in my view, just slowing the journey for no safety benefit. Signals may be a different matter, and a policy of treating the two differently could actually improve safety.

Surely if you use maximum brake there is no margin for error.

 

[ComUtoR]

Not counting emergency slam on the breaks, often wondered under dry conditions how far from a station a train going at or over 100mph would start to slow down.

Enough distance to go "wheeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeeee"

 

[HarleyDavidson]

Surely if you use maximum brake there is no margin for error.

One of the things about route knowledge is that you learn, your earliest, normal & latest braking points to a station, so that you have all of the bases covered, so as a driver you can use the earliest one for low adhesion, normal for everyday working and your latest one for making up time.

However the art is to know when to use them and use them in the optimal way, for example you wouldn't dream of approaching a station like Winchester on the down at 100 with a booked call in the autumn and in the morning when it's damp as you'd go sailing straight through and end up somewhere near St Cross!

Yet you could do it on a dry summer's day without issue. It's all about balance and the art of driving & knowing your stuff.

 

[Starmill]

Regarding the point about maximum braking and professional driving, what do drivers think of the distinction some people like to make between maximum braking and decelerating into the platform, and decelerating down to low speed before the train has reached the platform and then just coasting or braking very lightly for the remaining distance to your stopping point?

 

[HarleyDavidson]

Regarding the point about maximum braking and professional driving, what do drivers think of the distinction some people like to make between maximum braking and decelerating into the platform, and decelerating down to low speed before the train has reached the platform and then just coasting or braking very lightly for the remaining distance to your stopping point?

To me and a quite a few others, entering a platform at a low speed offers more & greater opportunity to accidentally stop short and leave the tail of the train out & off the end of the platform, whereas if you come in at speed say 30+ then you're looking to the appropriate stop mark and that's precisely what I & a considerable number of seasoned drivers do.

I can understand it if there's a red signal at the end of the platform fine, as that's one of the rules I do abide by now, 15-20 at the "magnet", but if I have the road all the way through, provided the rail is good, then I'll come in at a speed that I feel comfortable with and know I can stop without issue.

It's all about balance.

 

[100andthirty]

I think that a stop on a Pendolino journey adds about 5 mins to the journey, which was part of the original question.

 

[Ploughman]

I had cause to wheel out the distance from point of impact to front of Cross country unit that had been travelling at about line speed of 90 - 100.
I made the distance as just over 800 metres.
The investigators checked their figures and it tallied fairly close with a full emergency brake application.
1 wheelset was derailed at impact and a second about 50 metres from stop point.

 

[plastictaffy]

I think that a stop on a Pendolino journey adds about 5 mins to the journey, which was part of the original question.

That's because they are extremely slow to accelerate away. Pendolino's are designed with sustained high speed running in mind. Desiros leave them for dead up to about 75-80mph. Leave MKC on the up on the xx47 stopper at the same time a Pendolino on the express xx47 and you're often going over Denbigh Hall North before he eases past you.

 

[notadriver]

One of the things about route knowledge is that you learn, your earliest, normal & latest braking points to a station, so that you have all of the bases covered, so as a driver you can use the earliest one for low adhesion, normal for everyday working and your latest one for making up time.

However the art is to know when to use them and use them in the optimal way, for example you wouldn't dream of approaching a station like Winchester on the down at 100 with a booked call in the autumn and in the morning when it's damp as you'd go sailing straight through and end up somewhere near St Cross!

Yet you could do it on a dry summer's day without issue. It's all about balance and the art of driving & knowing your stuff.

I would never use the full service braking curve all the way in even on a dry day. That's asking for trouble. I always leave a fair bit in reserve.

 

[HarleyDavidson]

I would never use the full service braking curve all the way in even on a dry day. That's asking for trouble. I always leave a fair bit in reserve.

I guess it comes with having the confidence to do it, also when you use 100% of the brake, you're actually not because you have another bit more for emergency brake and OMG you chuck a Desiro into Emergency, you come up fast and that's fast with a capital F!

Even our 455/456 fleet has enhanced emergency braking and emergency on them is darn good too. Used it a while back to avoid hitting a Doe & a fawn and yes I missed them!

 

[notadriver]

Excuse me but I know 100% brake isn't all of it and I also know there's a fair bit more if I go into emergency but that's the point - it's for emergencies *sigh* .....

 

[Deepgreen]

With a class 45 plus 3 mark 1s on, I believe about 150-200 metres was achieved from 100+mph, albeit with a nuclear flask in the way!