Why are certain tube lines noticeably warmer and vice versa

[Silent]

I get the Victoria line and Jubilee line quite often and notice the latter is much cooler. I don’t think I’ve ever found it overly warm.

The Victoria line isn’t always super warm but usually is very warm and stuffy. I use the Bakerloo line as well and although it’s also warm it doesn’t feel as warm or stuffy as the Victoria Line.

I’ve read that Piccadilly and Jubilee, excluding the W&C, are the coolest deep level lines. I think that’s because both ends of the line are overground. But then Central line is still a really warm line? Maybe the tunnel section is longer?

I also notice the Jubilee line probably goes as fast and faster, looking at the top speed, than the Victoria line but I think it accelerates and brakes slower than the Vic Line maybe that causes extra heat.

I can imagine how hot Victoria lines rails are being the second most frequent train service in the world.

 

[Snow1964]

There are multiple factors :
- tunnel diameter (affects piston affect of air being pushed through)
number of ventilation shafts
- braking system (they used to get even hotter when trains 100% used friction brakes rather than regenerative brakes)
- station configuration, older ones were originally built with lifts accessed by narrowish passageways, later ones with wider concourses and escalators, and some were modified so affects airflow to platforms
- train control system (the older control systems used rheostats (which cooled by throwing out heat like old electric bar fire)
- train ventilation system (fans extracting warm air into tunnels etc)

So combinations of history of tunnels and their ventilation, and features of train depending on its age

 

[Magdalia]

I have lots of experience of travelling on the Victoria line though it is all a long time ago now. It has always been horrible in hot weather.

The main factor is the temperature of the air above ground. In periods of prolonged hot weather the ventilation caused by the movement of the trains during the daytime draws hot air underground which then gets trapped. This is partly because fewer trains run in the hours of darkness when the air above ground is cooler.

The Victoria Line is particularly badly affected because it is all underground (apart from the depot at Northumberland Park) and it has a bigger proportion of its total length in Central London where daytime temperatures above ground are highest.

 

[announcements]

I still remember the heatwave a couple of years ago; for once it was hotter outside at street level than it was on the Victoria line!

I use the Victoria line every day and from my own observations, it is the hottest. The Central line tends to be the line that gets all the stick for being the hottest line thanks to internet meme culture; I can only assume this is because of the connotations of the word 'Central' that makes for a more amusing/empathetic meme. In reality, whilst the Central line can get hot, it's not as hot as the Victoria line in my experience. I suspect the situation has become worse since the introduction of the '09 stock.

The Piccadilly line, on the other hand, does feel cooler. There is particularly good ventilation on the northern end of the line.

 

[Silent]

I still remember the heatwave a couple of years ago; for once it was outside at street level than it was on the Victoria line!

I use the Victoria line every day and from my own observations, it is the hottest. The Central line tends to be the line that gets all the stick for being the hottest line thanks to internet meme culture; I can only assume this is because of the connotations of the word 'Central' that makes for a more amusing/empathetic meme. In reality, whilst the Central line can get hot, it's not as hot as the Victoria line in my experience. I suspect the situation has become worse since the introduction of the '09 stock.

The Piccadilly line, on the other hand, does feel cooler. There is particularly good ventilation on the northern end of the line.

I agree, I remember seeing an old vid from when 09 stock were being built and it talked about better ventilation but the fans maybe accentuate the stuffiness now.

 

[Recessio]

Geoff Marshall did a video a few years ago, where he measured the temperature in each line. Bakerloo was hottest, then Central, then Northern, then the Victoria.

One concern about adding air conditioning to the 2024 stock is that the heat has to go somewhere. Even if the trains are now cool, the stations will still be hot(ter) which could still lead to passengers fainting. I remember there was that amazing trial cooling at I think St Paul's station? Did anything ever come of that, because it seemed to work really well!

 

[Dstock7080]

Trial fittings of cooling equipment at Holborn (disused) platform and other trials already undertaken, will be used at some Piccadilly stations in the future.
Along with fan overhaul at many of existing shaft sites.

 

[Meerkat]

Isn't it partly to do with how old particular lines are?
Until I saw things like the video linked above it hadn't occurred to me that underground should be cooler than the street, but the system has raised the surrounding ground temperature drastically.

At a top level it feels like all this heat should be worth something but extracting it from under London is presumably rather tricky (I know they are using heat from the tube for community heat and power somewhere on the system?)

Re the 2024 stock IIRC they believe the heat output from the air-con will be negated by the train being lighter and re-generative braking reducing heat output.

 

[Recessio]

At a top level it feels like all this heat should be worth something but extracting it from under London is presumably rather tricky (I know they are using heat from the tube for community heat and power somewhere on the system?)

Bunhill heat network, at the disused City Road Station on the Northern line. I think connecting a load of heat pumps and making district heating networks would be an excellent idea!

 

[Silent]

Isn't it partly to do with how old particular lines are?
Until I saw things like the video linked above it hadn't occurred to me that underground should be cooler than the street, but the system has raised the surrounding ground temperature drastically.

At a top level it feels like all this heat should be worth something but extracting it from under London is presumably rather tricky (I know they are using heat from the tube for community heat and power somewhere on the system?)

Re the 2024 stock IIRC they believe the heat output from the air-con will be negated by the train being lighter and re-generative braking reducing heat output.

Victoria Line isn’t old compared to Piccadilly Line though and I’m sure the train have regenerative braking.

 

[bramling]

I get the Victoria line and Jubilee line quite often and notice the latter is much cooler. I don’t think I’ve ever found it overly warm.

The Victoria line isn’t always super warm but usually is very warm and stuffy. I use the Bakerloo line as well and although it’s also warm it doesn’t feel as warm or stuffy as the Victoria Line.

I’ve read that Piccadilly and Jubilee, excluding the W&C, are the coolest deep level lines. I think that’s because both ends of the line are overground. But then Central line is still a really warm line? Maybe the tunnel section is longer?

I also notice the Jubilee line probably goes as fast and faster, looking at the top speed, than the Victoria line but I think it accelerates and brakes slower than the Vic Line maybe that causes extra heat.

I can imagine how hot Victoria lines rails are being the second most frequent train service in the world.

There’s so many factors it’s hard to make proper comparisons, and indeed I’m not sure one can say that one line is hotter than others as different parts of the same line vary.

However it’s probs my fair to say that the two main factors are the design of the ventilation, and what braking system is used by the trains.

The Victoria Line was built with many more ventilation shafts than much earlier lines, and they were generally fairly well sited, but this seems to have been negated by the rheostatic braking on the 67 stock, which really pumped out a lot of heat. The Jubilee line always seemed better ventilated, but tended to have a sparser service than the Victoria Line.

Much of the Bakerloo has little ventilation at all. I think on balance this probably contains sections which are consistently hottest.

The Victoria Line I’d say has got a lot cooler over recent years overall, no doubt due to upgrading of the ventilation shafts, and the regenerative braking on the new trains.

 

[announcements]

Much of the Bakerloo has little ventilation at all. I think on balance this probably contains sections which are consistently hottest.

The Victoria Line I’d say has got a lot cooler over recent years overall, no doubt due to upgrading of the ventilation shafts, and the regenerative braking on the new trains.

New article today on the topic: https://www.ianvisits.co.uk/article...e-line-in-2023-surpassing-central-line-74310/

The Bakerloo is one of the hotter lines, but not as hot as the Victoria line. If anything, the Bakerloo line is probably the "stuffiest" if that makes sense - going by the air quality, denseness and smell! That makes sense given the lack ventilation, as you say.

 

[Silent]

There’s so many factors it’s hard to make proper comparisons, and indeed I’m not sure one can say that one line is hotter than others as different parts of the same line vary.

However it’s probs my fair to say that the two main factors are the design of the ventilation, and what braking system is used by the trains.

The Victoria Line was built with many more ventilation shafts than much earlier lines, and they were generally fairly well sited, but this seems to have been negated by the rheostatic braking on the 67 stock, which really pumped out a lot of heat. The Jubilee line always seemed better ventilated, but tended to have a sparser service than the Victoria Line.

Much of the Bakerloo has little ventilation at all. I think on balance this probably contains sections which are consistently hottest.

The Victoria Line I’d say has got a lot cooler over recent years overall, no doubt due to upgrading of the ventilation shafts, and the regenerative braking on the new trains.

The bakerloo line which I use sometimes feels cooler than the Victoria line but I’ve only used them consistently this year.

I used the bakerloo line in the 2022 heatwaves and it was probably hotter then. It was hot overground.

This year hasn’t been super hot in London.

 

[DynamicSpirit]

One concern about adding air conditioning to the 2024 stock is that the heat has to go somewhere. Even if the trains are now cool, the stations will still be hot(ter) which could still lead to passengers fainting.

While that's strictly speaking true, I would imagine that in practice, the difference made to the air in stations is small. You have to remember that in normal running the distance between trains is far greater than the length of each train. Add that to that the vast majority of station platforms are much wider and higher than the interiors of tube trains. Those factors combined mean that the volume of air inside trains is much smaller than the volume of air outside trains in tunnels and stations: So the heat removed from trains is spread out into a much greater space, which proportionally reduces the temperature increase.

 

[Silent]

While that's strictly speaking true, I would imagine that in practice, the difference made to the air in stations is small. You have to remember that in normal running the distance between trains is far greater than the length of each train. Add that to that the vast majority of station platforms are much wider and higher than the interiors of tube trains. Those factors combined mean that the volume of air inside trains is much smaller than the volume of air outside trains in tunnels and stations: So the heat removed from trains is spread out into a much greater space, which proportionally reduces the temperature increase.

Don't they have an air cooling system rather than true AC. What is the difference of air cooling to air conditioning.

 

[rebmcr]

What is the difference of air cooling to air conditioning.

Air conditioning also provides control of humidity.

 

[Recessio]

Quite common to not have humidity control on trains (or cars), just cooling

 

[Egg Centric]

Quite common to not have humidity control on trains (or cars), just cooling

Are you sure about the car bit?

 

[rebmcr]

Quite common to not have humidity control on trains (or cars), just cooling

There might not be selectable settings for the control of humidity, but it's inherent to the operation of air conditioning.

 

[Silent]

Why does the 2009 tube stock fail to cool the air that the carriages suck in from the tunnels.

 

[Dstock7080]

Why does the 2009 tube stock fail to cool the air that the carriages suck in from the tunnels.

There are no coolers on the train, it just sucks in the air lower in the tunnels, which in LU theory would be cooler.

 

[announcements]

The question is how regularly do they still clean those tunnels from which the "cool air" is being drawn in?

 

[Silent]

There are no coolers on the train, it just sucks in the air lower in the tunnels, which in LU theory would be cooler.

So the news presenter provided misinformation. But I guess that’s normal as I know the evening standard got it wrong when the news presenter was saying the last new tube trains were Jubilee line when viewing the new pic line trains.

 

[Dstock7080]

So the news presenter provided misinformation.

Think you need to listen again, the transcript is:
“Phwor! this a relief, cool air on an Underground train on a hot day. Because on the Victoria Line these new trains are gonna have air that’s cooled outside in the tunnel, pumped in and brought to commuters at face level when they stand on a busy train.”

 

[Silent]

Oh that makes sense but the air doesn’t feel like it has been cooled

 

[Bikeman78]

Geoff Marshall did a video a few years ago, where he measured the temperature in each line. Bakerloo was hottest, then Central, then Northern, then the Victoria.

One concern about adding air conditioning to the 2024 stock is that the heat has to go somewhere. Even if the trains are now cool, the stations will still be hot(ter) which could still lead to passengers fainting. I remember there was that amazing trial cooling at I think St Paul's station? Did anything ever come of that, because it seemed to work really well!

That is surprising. Last week I switched from the Bakerloo line to the Victoria line at Oxford Circus. The waft of heat as I walked across the passage was like opening an oven door.

 

[Bald Rick]

That is surprising. Last week I switched from the Bakerloo line to the Victoria line at Oxford Circus. The waft of heat as I walked across the passage was like opening an oven door.

Thats intetesting, as I did the opposite last week (Vic - Bakerloo), and thought the Bakerloo was hotter!

 

[Silent]

That is surprising. Last week I switched from the Bakerloo line to the Victoria line at Oxford Circus. The waft of heat as I walked across the passage was like opening an oven door.

Yeah I think now Victoria Line is warmer but previous years it was bakerloo line. I wonder if that is because of cooler weather this year as bakerloo goes above ground. I also noticed last time I recently used the bakerloo line it’s carriage fans was actually making the air feel breathable unlike the Victoria line which the fans just add to the stuffy air.

I use both lines quite daily between Baker Street and Victoria.

 

[DynamicSpirit]

I don't use the Victoria line very often, but when I have used it, I've generally had the impression of it being hotter than the other lines. My assumption was that that was probably because it's a much more frequent service than the other lines, and maybe a bit because of it being entirely underground too.

On the other hand, the Northern line feels the worst for air quality. When I'm changing from Elizabeth line at Tottenham Court Road, the change in smell as you approach the Northern line platforms is very obvious.

 

[Bikeman78]

Thats intetesting, as I did the opposite last week (Vic - Bakerloo), and thought the Bakerloo was hotter!

To be fair, it probably depends on the outside temperature. It was 23 degrees on the day in question. If it's 30 degrees outside then the Bakerloo stock will drag that heat into the tunnel. Are there any plans to do anything about the Victoria line? It was my first ride in over a year and I found it borderline unbearable, even for four minutes.