Speed Restrictions due to Heat

[carriageline]

If the sun is beating down on a metal product for hours on end, it's going to be hotter than the air. Take your car for example.

 

[Boodiggy]

It's not just the rails that are the issue. The main reasons for heat related speeds are ballast disturbances, such as tamping, lifting and packing, track renewals etc.
For CWR the issues can be under stressed track or ballast shortage.
For Jointed track it can be the the gaps at the rail ends are incorrectly set. Rail gaps are adjusted as required before the on-set of hot weather.
All of these things give the track a lower critical rail temperature and within each CRT there will be a watch temperature (W), a 30/60 temperature, at which a speed restriction of 30/60 will be imposed and a 20 temperature, which means when a certain temperature is reached a 20 will be imposed. For ballast shortage there is no 30/60, after the watch temperature the next trigger is the 20. Depending on location a 20 may need to be imposed at the watch temperature, this is if the track cannot be inspected safely by staff at locations with curves etc with limited sighting of trains. There is a lot more to it than rails getting hot.

 

[Eagle]

This is ridiculous I'm delayed by an hour now just because its 25 degrees out.

25 °C air temperature in the shade. Ground temperature in the sun (particularly on railway lines, where the metal and ballast absorb a lot of heat) is probably closer to 55 °C.
--- old post above --- --- new post below ---

I'm not an engineer, I'm a customer. However it cannot be beyond the wit of someone to lay rails that don't distort in moderate heat, that can design an electrical supply system that continues during cold and frosty weather, that is capable if lopping trackside trees down.

Clearly it is beyond the wit of man. Otherwise it would already have been implemented. Duh.

I don't get this ridiculous idea that there is some easy solution but the railway is choosing not to use it because they can't be bothered. Trust me, it's a very big problem for the railways, and I'm sure there are many engineers worldwide researching ways to solve the problem in an affordable way. But as it stands there isn't a solution. Or at least not one that's affordable.

So stop whining and accept that as it stands it is an insurmountable problem.

 

[HSTEd]

Could just deploy slab track with the rails and slab painted white.

But slab track would cost quite a bit of money despite it probably saving money overall in generally reduced maintenance and the like. (Since the slab is infinitely more resilient than loose piles of stone)

In other words, there are a large number of partial solutions but the accountants undoubtedly believe it is cheaper just to put up with it.

 

[michael769]

Clearly it is beyond the wit of man. Otherwise it would already have been implemented. Duh.

I guess the folks who run trains through Arizona are not men then?

 

[Trog]

No need to paint slab track as being rigid it will stay in place on its own. However the movement inherent in the more resilient ballasted track, can be a weakness when it comes to resisting the compressive forces generated by heat. In that as the track moves under the passage of a train there is a tendancy in weak track for it to move in the direction that reduces the compression but then spring back less.

Also the problem with heat is not so much high temperature, but temperature range.
If the temperature is always high you stress to a high temperature, no problem.
If the tempeature is always low you stress to a low temperature, no problem.
If you have a large temperature range you have to pick a middling temperature so that your rails do not snap at the least defect in a frost, but also do not buckle on the first hot day. But then at the far ends of the temperature range you get problems at points of weakness.

 

[Eagle]

I guess the folks who run trains through Arizona are not men then?

The difference there is that it is hot all the time, rather than just for a few random days in the summer. Being as that makes the problem a lot bigger, it's therefore a lot more appropriate to spend the large amount of money needed to fix it, whereas in the UK it's not worth it.

 

[michael769]

But you said it was insurmountable. Clearly it is not.

Expensive is not the same thing as insurmountable!

FWIW I agree that it is not worth spending vast sums to make a network that is resilient to all possible conditions. But it was no especially hot today by UK standards.

 

[Eagle]

It's insurmountable in this country because it's prohibitively expensive for the size of problem it is.

Happy now?

 

[Darren R]

Not gonna get drawn into the whole 'why does this always happen when the sun comes out' thing, but I do have a genuine question: It always seems to be certain areas/routes that suffer TSRs due to the heat, of which the Waterloo area is one. Why is this? Why are some areas prone to this, whereas others less so? (And I don't mean because it never gets above 20C in Scotland and London is always the hottest area in the country!)

 

[The Barlow Boy]

If the sun is beating down on a metal product for hours on end, it's going to be hotter than the air. Take your car for example.

I often do rather than the train.........

 

[Eagle]

Why is this? Why are some areas prone to this, whereas others less so?

I've never been particularly sure of this, but one factor has got to be how much sunlight it receives (the hottest part of the day is mid-afternoon, so unshaded lines running SW to NE will get the worst of the sun). But there's got to be more factors to it than that.

 

[Darren R]

I've never been particularly sure of this, but one factor has got to be how much sunlight it receives (the hottest part of the day is mid-afternoon, so unshaded lines running SW to NE will get the worst of the sun). But there's got to be more factors to it than that.

I did consider this (and I'm guessing it may play a part) but the approach Fenchurch Street on the viaduct is just as exposed to the mid-afternoon sun, but doesn't seem to have the problems. Of course it's a much simpler layout though - is this also a factor?

Incidentally, it's not just the railways that don't like the heat - neither does my internet connection! (****** thing keeps dropping out! Only in Lancashire!:roll

 

[Bald Rick]

I guess the folks who run trains through Arizona are not men then?

other differences being

a) they don't fiddle with their tracks as much as we do, and it is the post fiddling period you need speeds on for when it is hot

b) it is predictably hot in Arizona every summer, this means they can predictably take precautions, such as restressing a whole line. Not feasible when it is hot one fortnight every few years sometime between April and October.

c) the tracks have lower line speeds than ours. Difficult to put a 60TSR on a route that is 60.

d) punctuality in the boonies is measured in hours not minutes. When speed restrictions are applied (and they are), it doesn't matter...

e) they don't care as much as we do about trains falling off. Pretty regular occurrence on US railroads.

 

[transmanche]

Well I'm not an engineer, so I did a bit of Googling to try an understand what's going on. And I have learned something, I now know what this is:

(I often did wonder what the odd bit of occasional double-rail in the middle was all about.)

Wikipedia's article on LGV track construction says that expansion joints are often used near bridges, but suggests that otherwise the stress levels are set to absorb strain. Do they (and don't laugh) change the stress/tension levels according to the season? Or just set different tolerances in different parts of the country?

 

[Peter Mugridge]

The suburban service fell apart at Waterloo this evening as a result of the restrictions, but control did manage very well to keep things going fairly evenly to all destinations, albeit with some delays of 30 minutes or so, mainly due to late inbound stock.

 

[cyclebytrain]

The answer could be to run the water jetter as they do during leaf fall and spray the rails with water to cool them, now there is a good idea.

Now this seems like a rather neat system and worth a trial.

 

[455driver]

Now this seems like a rather neat system and worth a trial.

How long do you think the effect would last?
If you could get enough water on the rail to cool it sufficiently what sort of stress would the rapid cooling have on the rail?
What sort of speed would the water cannon train need to run at to cool the rails effectively?
What happens to the passenger trains that would normally be using the line the water cannon is travelling (very slowly) on?
Who picks up the delay minutes?

 

[HSTEd]

Slab track formations in Germany used for moderate speeds have lasted decades with no major maintenance beyond rail grinding (which can be done at 60mph now), while I don't think the track formation in the Chunnel has required much work on it at all despite the obscenely heavy use it sees day in day out. (Several several thousand tonne trains every hour).

I think it is worth it, especially considering the low capital costs the government could recieve now that would allow it to recover its investment in reduced subsidies.

 

[martybabes]

Cue the rail haters and anti-rail haters (and the anti-anti-rail haters et al)

So why doesn't the TGV run at 35 kph on hot days? I remember leaving Avignon on a hot day and we reached Paris on time after travelling at a good old lick. And it is not as hot as Arizona in the south of France every day - I've been there (Provence) on days when it is cool, and days when it is very windy (as in Mistral windy).

Maybe we should take a tip and learn from from Les Grenouilles...

 

[Monty]

Cue the rail haters and anti-rail haters (and the anti-anti-rail haters et al)

So why doesn't the TGV run at 35 kph on hot days? I remember leaving Avignon on a hot day and we reached Paris on time after travelling at a good old lick. And it is not as hot as Arizona in the south of France every day - I've been there (Provence) on days when it is cool, and days when it is very windy (as in Mistral windy).

Maybe we should take a tip and learn from from Les Grenouilles...

I imagine the volume of traffic does all come into play at some point, how many trains does that line see in an hour? No where near as many as the line from Clapham to Waterloo that's for sure. I also suppose it helps that France's TGV network is engineered to more modern standards that some parts of our network.

 

[michael769]

It's insurmountable in this country because it's prohibitively expensive for the size of problem it is.

Happy now?

No. That is not what insurmountable means.

It means that there is no solution in existence. Not that a solution is too expensive.

 

[TDK]

How long do you think the effect would last?
If you could get enough water on the rail to cool it sufficiently what sort of stress would the rapid cooling have on the rail?
What sort of speed would the water cannon train need to run at to cool the rails effectively?
What happens to the passenger trains that would normally be using the line the water cannon is travelling (very slowly) on?
Who picks up the delay minutes?

Who knows how long it will last

Same as if it rains on a hot day

Once again who knows but if it is over 20mph (the blanket speed normally imposed) The jetter will be held up by the normal services

Delay minutes will be picked up by whoever picks them up for the rail heat

 

[broadgage]

Of course we would all prefer to arrive late than not at all, but in recent years there does seem to have been an increase in hot weather delays.
Yesterday though the hottest day of the year so far was by no means exceptional as compared to previous years.

The delays seemed quite substantial, with a number of cancellations, overcrowding, and according to newspaper reports, buses instead of trains for one branch.

I dont remember this being such a problem years ago.

 

[Flamingo]

Of course we would all prefer to arrive late than not at all, but in recent years there does seem to have been an increase in hot weather delays.
Yesterday though the hottest day of the year so far was by no means exceptional as compared to previous years.

The delays seemed quite substantial, with a number of cancellations, overcrowding, and according to newspaper reports, buses instead of trains for one branch.

I dont remember this being such a problem years ago.

I do.

 

[MadCommuter]

So why doesn't the TGV run at 35 kph on hot days? I remember leaving Avignon on a hot day and we reached Paris on time after travelling at a good old lick. And it is not as hot as Arizona in the south of France every day - I've been there (Provence) on days when it is cool, and days when it is very windy (as in Mistral windy).

Maybe we should take a tip and learn from from Les Grenouilles...

I am guessing here, but I would imagine the metal mix in French rails is different as they have average higher temperatures than the UK. Ours have to endue a generally harsher winter so are more geared to that. Happy to be corrected if I'm wrong.

 

[455driver]

Cue the rail haters and anti-rail haters (and the anti-anti-rail haters et al)

So why doesn't the TGV run at 35 kph on hot days? I remember leaving Avignon on a hot day and we reached Paris on time after travelling at a good old lick. And it is not as hot as Arizona in the south of France every day - I've been there (Provence) on days when it is cool, and days when it is very windy (as in Mistral windy).

Maybe we should take a tip and learn from from Les Grenouilles...

How many sets of points and how sharp are the curves on that line?

I mean lets compare a very old, very complicated, very curvy section of a very busy commuter railway with a straight piece of modern high speed line! :roll:

How do the ordinary lines in France compare with their 3 trains a day?

 

[YorkshireBear]

How many sets of points and how sharp are the curves on that line?

I mean lets compare a very old, very complicated, very curvy section of a very busy commuter railway with a straight piece of modern high speed line! :roll:

How do the ordinary lines in France compare with their 3 trains a day?

Hit the nail on the head there.

 

[infobleep]

Could just deploy slab track with the rails and slab painted white.

But slab track would cost quite a bit of money despite it probably saving money overall in generally reduced maintenance and the like. (Since the slab is infinitely more resilient than loose piles of stone)

In other words, there are a large number of partial solutions but the accountants undoubtedly believe it is cheaper just to put up with it.

If it is cheaper to put up with it why don't they publicly say so. Alas no large organisation in this country likely to say it's not worth doing anything because all the newspapers and some of the public will criticise them. I think the main issue for them is the newspapers criticising them rather than the public.

I do not mind being delayed if someone or some company is happy to openly admit this is the case. If they could ever incorporate more accurate delay times, in advance, into the live departure and arrival boards that would be good. Last night I took a chance that the listed on time train would end up being 10 minutes late by the time I reached the station (20-30 minute walk). It was.

 

[martybabes]

How many sets of points and how sharp are the curves on that line?

I mean lets compare a very old, very complicated, very curvy section of a very busy commuter railway with a straight piece of modern high speed line! :roll:

How do the ordinary lines in France compare with their 3 trains a day?

Ah - so it's not down to the heat. It all depends on how busy the line is.

Well, that's sorted then!