The Piccadilly line’s new air conditioned trains | Hacker News Reader

The Piccadilly line’s new air conditioned trains

ianvisits.co.uk

225 pointsedward219 comments

The issue is that a major point of this upgrade was defeated as the article slightly mentions, but doesn't dwell on it: the signalling upgrade that the line sorely needs was axed during the Covid TfL budget crisis negotiations and is not coming back. The whole point of the "New Tube for London" project was that new modern trains were tied to signalling upgrades, which would let more trains run on the existing lines in a more reliable way.

The trains were already ordered so will be delivered, with the associated flashy benefits of new carriages, but now the line capacity won't increase, so you'll still get the same breakdowns and delays that currently happen now. The Piccadilly line also won't be able to stop at the stations it currently skips (since they don't want to delay service any further than now) – making the Piccadilly Line stop at some of the stations it currently skips was also tied to the signalling upgrades.

It's classic top-down "you need to cut on costs" decision making leading to having to make compromises on a project in a way that it'll still cost a bunch of money, but without a major benefit at the expense of a (comparatively) small cost saving. You see this in software engineering all the time too.

This isn't completely correct. There is going to be an increase of capacity even without resignalling from 24tph to 27tph. It's also not a low cost thing, the SSLs resignalling cost at least £1.6bn and has been horrendously delayed. While the pic line is less complex than the SSLs, there has been ridiculous cost inflation on all rail projects, so I would not be surprised if it costs a similar amount of money. In comparison the new trains cost £1.5bn so it's basically the same again to resignal the line to ATO.

I also believe the new trains can accelerate faster so new stops are potentially possible. And in theory at least they should be a lot more reliable, even if the signals aren't.

FWIW there was a signals redesign contract for the pic singed in 2022 so I don't think it's never going to happen. Also even before covid it was phased that the new trains and signalling where fairly independent projects.

Correct – that's the stated 10% capacity increase of the new trains. It's not nothing.

My disappointment comes from the fact that there are stations where the Piccadilly just blazes through and doesn't stop. The platforms are there, maintained and in use, but the train just goes past. Those areas have been repeatedly told for the past decade "no new stops until signalling upgrades which you'll get when the new trains come – otherwise it would make the journeys longer and we can't have that on a line that services Heathrow!".

Now the time has come and the signalling upgrades were axed, meaning according to the original logic, no chance of getting the trains to stop at your station. Of course new stations could be serviced, at a cost of making the journeys slower – surely the argument of "if the train stops at your station, it'll slow down the journey for everyone" applies to all stations, not just a select few? But even if we go with the nonsensical "we can't slow down the average journey time", other options could be taken, such as making the trains stop at the least used stations alternately – you don't even need to go full "Express Train" route NYC does if your issue is just a couple of stations.

Still, TfL hasn't really shown any interest in touching any that and always said "you'll get your stop with the new trains". Well, the new trains are almost here and it doesn't look like it'll come with a solution, just more of the status quo.

Air conditioning is of course great and I'm not advocating for maintaining old stock forever. But a shiny new train does nothing if the train won't stop at your station. And you're not going to get much gains if your shiny new trains are effectively throttled to last century speeds with last century reliability.

The capacity increase is 10% in terms of trains per hour and another ~10% in terms of how many people you can fit in the train, so it's nearly 25% pax carrying increase. Given tube numbers are down 20%, since covid, this is a huge improvement in space per passenger.

I think you are really overegging the impact of the skipped station (turnham green?) You can just get a district line train and change. Ok, it's not ideal but it's probably only adding 5-10mins to journey times. It's one station on a network of hundreds and does not justify billion+ spent for it.

And I don't think there is a business case for further capacity, as not only would it require resignalling it requires another batch of trains to be built to get it up to 36tph. There isn't the demand for that post covid. This may change but there are much more pressing captial projects for tfl (bakerloo line extension for example) imo.

The funny thing is the increased capacity wasn't necessarily the biggest driver for this upgrade. Part of the selling point to Boris Johnson who was mayor at the time was that he could stick it to the train driver's unions (who were having a big fight with him at the time) by introducing automatic train operation.

The problem with relying on post COVID passenger reductions is that whilst tube numbers are down 20% since COVID that just means they're at the level they were in 2009/10. Even if they don't bounce back fully this year, post COVID working hasn't cut out the peaky nature of tube travel. Even if people work from home Monday and Friday, they'll often all come into the office on Tues-Thurs making peaks on those days.

I agree the demand for capacity on other lines that is even more pressing. Last time I rode the tube regularly was 10 years ago and even then I recall the Victoria line during rush hour was literally cattle class, your face in someone else's armpit. The 2019 numbers put the Northern Central, Jubilee and Victoria lines are well over the 100% mark at peak time. Despite having the highest comparative fares compared to other cities the Tube is still woefully underfunded. There is so much technical debt because much of the system was built in the 1800's and early 20th century. First mover disadvantage, because we got to make all the mistakes.

> surely the argument of "if the train stops at your station, it'll slow down the journey for everyone" applies to all stations, not just a select few?

No it doesn’t. Some stations serve more passengers and transfers than others. And even if stations were identical, the opportunity cost of stopping goes up as the train gets more full.

> such as making the trains stop at the least used stations alternately

Yes, this can make sense. But it doesn’t necessarily have to. You have to actually check the numbers.

IDK if they still do it but Chicago used to run "A" and "B" trains that would only stop every other stop. At some stations, all trains would stop so you could get off and transfer to the alternate train if you needed to.

So basically any given train was only stopping at maybe 60% of the stations.

I knew some buildings that had elevators that worked that way: one for even floors, one for uneven ones. I always wondered if this really paid off. I guess in a building you almost always are either going to or coming from the ground floor, and you never need to switch elevator. But on a train line you might want to get off at any stop so ~50% of people will need to switch.

I was curious about this too, so I decided to simulate it. It's a fun problem to model and code, with some entertaining places to trip up - for example, that brief awkward period where the elevator is full, but newly arriving people recognize they should not press the button until it leaves. In any case, the answer varies based on the rate of arrival - in some regions of the parameter space it's better if all elevators stop everywhere (intuitively, if odd people arrive every 2 min and it takes 3 min to go up and down, it becomes too expensive to have to wait for the odd elevator). But even in cases where interleaved floors performs better than all floors, there's a solution which is even better there - lower half of the floors on one elevator and the upper half (plus ground floor) on the other. This will make for a fun interactive notebook.

Turnham Green tube for example has platforms for the Piccadilly line and it actually stops after 10pm (or if there's a problem), but not at other times.

It's such a busy station for being a local station (out of the TfL station types, the least-used), and the District Line beyond this is often quite crowded at rush hour -- it's rare that I get a seat starting from Turnham Green at rush hour.

Having the Piccadilly stopping here during the day would allow for better passenger distribution -- I've often found that one or the other line is brimming with passengers even when the other is half-empty.

I’ve always suspected this is to accommodate for the last District line train to Richmond. However I’ve never checked the timetable to confirm when that is. This potentially allows users to reach this destination if they miss the last train at Hammersmith.

Similar to how the last westbound central line train to Ealing Broadway holds at White City to allow the final westbound train of the night (towards West Ruislip) to transfer the last stragglers from the city

They just stop late (and early) for the more mundane reason of 'because they can', the service is less frequent at off-peak times so there's enough time to stop at Turnham Green before the train behind catches up.

In NYC, faster-accelerating subway trains, with not-better brakes, actually caused slower subway service. The coarse-grained signaling had to assume the worst case: a subway train that started max acceleration (operator fainted on gas pedal?) just after a signal, and wouldn't have emergency brakes automatically tripped until the next signal. So faster accelerating cars can get faster in that segment, and require keeping more signal-blocks of spacing between trains for max emergency braking distance. (So, really the fault of old signals and brakes, but still, faster trains had slower service :) https://homesignalblog.wordpress.com/2022/12/21/how-we-slowe...

> It's also not a low cost thing, the SSLs resignalling cost at least £1.6bn and has been horrendously delayed.

Pardon my ignorance, but how can a signaling system cost that much money? Is it made out of gold and platinum or what?

The main three things are:

1) very complicated and drawn out design/approval processes with many expensive consultants involved. on network rail you would not believe the amount of studies they have to do, including testing the light levels everywhere in a carpark to make sure there are no dark spots, amongst a billion other small things. there has been endless regulation forced on the railways/tfl, which on one hand is good for safety but on the other has meant even a tiny project needs a trillion risk assessments done, which typically get outsourced to specialist consultants, who have a massive incentive to find problems so they can retest.

2) lack of competition at the top level contractor layer. the procurement rules require really only huge companies can bid, which means they can act in a semi-cartel way. this is probably difficult to solve given signalling stuff but in more basic construction projects it feels like not much competition is going on (not suggesting there is a cartel here, fwiw, just feels a bit like it!)

3) on the tube the access is extremely restrictive. you tend not to close the line for extended periods of time (though this is changing recently as i think people are realising the cost of keeping the line isn't worth it vs doing a week closure), which means that you have to get all your equipment down to the tunnel (which might taken an hour), do 2-3 hours of work, then remove all the equipment, in 4-5 hour blocks each night between midnight and 5amish, which means you are paying people often "night working" wages for working really 2 hour shifts, instead of paying them normal wages for working through the day for 8 hour shifts. This probably increases the cost of labour by 5-10x.

That's the price of making complex, real-world hardware systems fail-safe. By fail-safe, I don't mean 'never fail' but, more literally, fail in a way that remains safe for all other systems interfacing with the failing one.

Proving that it fails safely requires a mountain of effort and documentation, but it's required because failure doesn't just lead to some speculative CPU bugs leaking a password or to a browser crash, it leads to many people dying.

To add to your point, the accident in Greece this summer that killed 50+ kids was attributed to human error that could've been avoided if they had upgraded their signalling system like it was promised decades ago.

I get that, but still, it is not like we don't have experience with making fail-safe things that we can draw from. And once you get a station + track fitted with the new system you just copy/paste; so I can understand a higher cost in the beginning for the proof of concept, but after that everything should be very cheap.

Ahhhh! "just" - the magic word!

It is not ever 'just'. This isn't copying code. This isn't building identical silicon for multiple end users. This is more like trying to add additional threads to something that is not embarrassingly parallel. What you're saying is like saying 'why can't you just make all of my computer programs run on all 32 of my CPU cores?'.

And even if you minimise the increasing complexity added by expanding the system, waterfall-style design (which is absolutely the most appropriate approach when dealing with these sorts of projects) front-end loads a frankly Herculean amount of risk management into the process because you want to make sure that's all absolutely square and true before you progress to implementation.

Lastly, it's worth noting that with systems this complex, a lot of the detail is bespoke because the number of complicating input variables the system is exposed to necessarily requires a relatively bespoke solution. Yes, the idea of e.g. ETCS being ETCS is going to hold, but how that works in reality, how it ties in to all of the other legacy systems, etc. will mean that you can't for example just take ETCS-equipped train A and and drop it into ETCS-equipped network B.

I was thinking that only the track sensors and traffic lights along the way need to be upgraded and the drivers would just drive trains as usual and they would be sequenced on a shorter distance/time between trains. I forgot that trains also have to be connected to the new system.

"you just copy/paste"

Aren't we talking about physical signalling kit - no copying and pasting? 272 stations and ~400km of track - a lot of which is pretty difficult to access?

He obviously meant copy and pasting the design. What did you think he meant?

I have no idea - that's why I was asking. I've been responsible for installing systems that had the same "design" into multiple physical locations - hundreds of physical devices at each location.

Having a common design does help but it doesn't help that much as most of the problems are with the physical realities of each location - and what I did was much simpler and less critical than signalling.

That’s less than £10 per rider of the line. Piccadilly line ridership is over 200 million trips per year.

This is a line that has 53 stations. For comparison that’s 20 more stations than the longest and highest volume L line in Chicago.

I wonder how this cost benefit compares to the $9 billion project to widen Houston highways?

What does £10 per rider of the line mean? How does that help us look at things?

I used to commute 5 times a week (often more) on Piccadilly. So that’s £5,200 for my ridership for the year? From that perspective seems rather expensive…

It’s disappointing they ditched the signal upgrades. It will bite everyone soon enough. Some of these systems date back over a hundred years, and are all incredibly bespoke.

Re the missed stations, I feel like they missed an opportunity with the Elizabeth Line line to shift more Heathrow traffic that way, giving some breather to Piccadilly during signal upgrades.

What do you mean by missed opportunity? To not run it there more frequently? Can't they still do that? The timetable has seen some updates already.

The average American spends $5,000 a year on the total cost car ownership, completely separate from public spending on roads and infrastructure, so I think that signaling cost is reasonable enough, especially since signaling will last far longer than the typical lifespan of a personal vehicle.

£5200 for your annual ridership but then divide that by the lifespan of the signaling. Let’s say it lasts 30 years, so that’s €173, (but of course, at the end of the 30 years £173 is worth a lot less).

How much an American spends on a car every year seems not that relevant to how much a British tube line signal upgrade costs. Why not compare it to house prices in London, and it'll seem even cheaper?

I compare it to automobile infrastructure because public transit infrastructure projects sems to be the only time anyone complains about high infrastructure costs.

The only reason I compare it to America is because I don't actually know the figures for the UK, but I expect that car owners would spend more there due to higher cost of petrol, higher vehicle taxes, etc.

Cars are unreasonably useful, though. If you're going anywhere to work / school / moving house / going on holiday / dropping kids at a friend's house, they work for a million uses.

That's why I don't think they compare well: many people who use public transport, even the Tube or similar, still need a car, at least sometimes. So it's not an alternative, and it's not equivalent value.

So probably better to pitch it not as £10 per rider (~200m annual riders) but £0.33/trip levy for the next 30 years.

I’m routinely surprised by how much things like this cost.

I think the answer is that solving this problem takes a teak of some size and skill, and paying them while making a hefty profit is expensive.

It’s compliance and bureaucracy that keeps competition out.

I think it has more to do with lack of state capacity. The agencies responsible for building this don't have anyone in-house anymore who can actually plan and carry out the job, instead relying on cascading layers of consultants and sub-consultants who manage contractors and sub-contractors.

Corruption

I had to look it up:

SSL = sub-surface line

I was amazed how well underground trains accelerate in Amsterdam and Munich. Also, how pleasant they are, and the interior design pleasantly fresh, with good amount of space and good-sized windows. That tube stock we have from the 70s looks really, really dated in 2020s. And the new ones look exactly the same, just even smaller windows? I can't imagine why they went ahead with that purchase.

How can they make the trains bigger when they're already as big as can fit in the tunnels?

(You can read the article to see the reason for the windows.)

It's a design issue, not a tunnel size issue. Look at all these interior details, not to mention a completely identical exterior. It's the rolling stock from the freaking past. Obviously there were so many cost-cutting measures (or somebody just pocketed all the money) that they took the original design, which was pretty cool half a decade ago, and just slapped an air conditioner on top of it. That's it, dude. That's everything we've got. What should have been done is a complete redesign of the car, and then they'd be able to figure out how to put all the A/C ducts without having to do all this windows crap. Hell, it's 2023. The age of rockets landing backwards. We should be having panoramic windows in these carts by now.

That is absolutely not it but sure, go off. The article covers improvements to various systems e.g. braking, wider doors, a fully walk-through carriage (consider how an end wall affects crashworthiness), additional headroom, as well as room for 10% more ridership capacity (bodies have to fit somewhere).

Moreover, there's something to be said about consistency of design when it comes to maintenance familiarity and parts interoperability. Consistent design language also tends to happen when you are catering to disability accessibility requirements and providing clear user interfaces for passengers (including those with disabilities, or those who do not speak English).

Lastly, expecting a complete redesign is committing to an astronomical amount of expense relative to even using just some of the old design DNA. However, I'm not even convinced they've just reused an old design. For starters, a different company did these (Siemens vs Bombardier) and secondly I'd bet that there's a whole lot of difference under the skin that is masked by the natural convergence of design appearance driven by the multitude of requirements set forth by TfL - everything from the design language mentioned above, to their access/egress requirements, fire safety, lighting, etc. etc. There's only so much money governments are willing to throw at figuring out how to skin that cat before it's just not worth it.

What do you expect to see out of these panoramic windows? The Piccadilly line is hardly the most scenic route in the UK; there's nothing to see but tunnel walls for more than half of the full line. I'm not arguing against panoramic windows if they're easily installed, but that seems to me like it should be a substantially lower priority than air conditioning on the deeper Underground lines.

Can you link to the Munich or Amsterdam metro trains? I just see fairly ordinary metro trains for a system with normal-size tunnels. The design is irrelevant to the small tunnels of the Piccadilly Line.

https://en.wikipedia.org/wiki/MVG_Class_C

https://commons.wikimedia.org/wiki/Category:M7_(Metro_Amster...

A better comparison is with the Circle/District/etc lines. Those trains are of similar size to the Dutch and German ones, although I think they are designed to carry a lot more people so there are fewer seats:

https://en.wikipedia.org/wiki/London_Underground_S7_and_S8_S...

> I also believe the new trains can accelerate faster so new stops are potentially possible.

Is accelerating faster a practical solution though, considering how many people are standing?

It’s bonkers. It stopes at South Ealing which is about 10 yards from Northfields but not at Turnham Green which is super busy.

Glad to see this top comment. I saw the headline and thought it would be more handwringing about climate change, a la "Look! Even northern Europe needs AC these days."

Cooling the trains is a relatively easy problem to solve these days. It’s cooling the tunnels and stations that’s the true engineering challenge.

I'm hoping the aircon filters will start clearing the filthiness of the tube air. Something tells me they'll have to change them more often then think.

Once you see it, you can't unsee it. There's this dark mist in the London underground, I find it very visible on the northern line, around elephant and castle. Just standing at one extreme of a platform and trying to look at the farthest part of the station, you'll realise everything is "foggy" by lack of a better term.

One hour there would turn my snot black.

There was a study on the TTC subway and they discovered the air quality was 10x worse than above ground and on par with Beijing. The accumulation of dusty linty particles on the walls has a cute name too "tunnel fur". I remember seeing workers going into the tunnels wearing N99 masks after that report was released.

I always like the (grease?) smell in Montréal Metro stations but never thought about it in terms of particulate matter concentrations.

Unfortunately the only smell I can associate with the Montréal metro is piss

I understood that the Montreal metro trains used wood breaks and peanut oil. Hard to say if that makes the same mess, but the rubber tires surely leave something. Also, the new rames may use different breaking technology.

They initially used different brakes, but they reverted to the good old peanut oil brakes because they had issues of some sort with dust.

I'm struggling to find a source that tells the reason, but here you can see they chose wooden brakes.

https://www.stm.info/sites/all/modules/custom/stm_import/imp...

One thing the article doesn't mention is that the trains are more efficient because they use regenerative braking, rather than friction brakes. The friction brakes cause a lot of the heat and dust in the underground.

By eliminating this heat, they are able to use that heat budget to run air conditioners on the trains and they still make less heat overall. As a side effect, the dust should be reduced too (and probably a bit of the maintenance)

There is actually an intermediate step between "friction brakes" and "regenerative braking" - electric trains can use the engines to brake, but the current produced is then fed to resistors, which dissipate it as heat, rather than used to charge a battery or to feed it back into the power supply line - https://en.wikipedia.org/wiki/Dynamic_braking#Rheostatic_bra.... So the friction brakes are actually only used when maximum braking is required - and these will also be needed with regenerative braking. Using regenerative instead of rheostatic braking will however lower the amount of heat produced I guess...

The 1973 trains already used rheostatic braking. The new ones use regenerative braking.

https://www.modernrailways.com/article/revolution-piccadilly....

http://www.trainweb.org/tubeprune/73%20tube%20stock.htm

There's another fun aspect of this -- combined with the lubrication, it leaves escalator rails near some lines absolutely filthy. I've got a pair of trousers permanently stained because I put my hand on the rail while walking down the escalator to the Northern Line at Embankment, didn't notice it had become absolutely covered in black gunk, and then touched my thigh.

This seems to be a problem almost exclusively on deep tube line escalators, in my experience.

I can understand that cooling a tunnel network like that is difficult, but surely filtering particles from the air is a solvable problem? Movable air filters on the platforms, etc.

Step 1 is to measure and declare a problem. To the best of my knowledge there's no systematic measuring of air pollution on the stations.

Same with loudness which on some (old) lines is way past safe.

Visiting London, there were two things I didn't understand about the underground.

1. Why is it _so_ hot in the tube? I can understand when the metro in Madrid gets hot, but London?!

2. How many people living in London, and taking the underground regularly, have hearing problems? How can a train be that loud and still be allowed to operate?! I've never experienced a train as loud as on the Victoria line.

1. https://www.wired.co.uk/article/central-line-temperature-lon...

tl;dr: when the underground was built, it was very cold down there (14C) to the point where people would go visit the underground in summer just to cool down. So no thought was build in the extra ventilation tunneling for future cooling it since it was already so damn cool.

But over the 100 years since then the trains and people have heated up the tunnels and stations, and since underneath London it's clay, it works as insulation so the heat never manages to dissipate, but rather gets trapped.

There are projects to add cooling to stations, but since they're old, deep, cramped and built in a dense metropolis that is already full of other stuff both above and underground, it is difficult and expensive to do.

I wonder if that could be a source of heat for district heating

For 1. There was a full writeup posted on HN about this a year or two ago. The answer is pretty much that the tube is far deeper than any other competing system and also is below things that can't be disturbed for ventilation shafts.

It's getting like 1-2 degrees hotter each year

Air quality is measured: https://tfl.gov.uk/corporate/about-tfl/improving-air-quality...

I can get real time air quality index above ground on multitude of places.

The most up-to date information on the tube I could found was this report[0], that only covered a number of stations. Even then, the information provided is not great, e.g. for Highbury & Islington:

> The results for particulate matter were between <0.02 and 2.16 mg/m3 for PM2.5.

Results cover the range from 4x of WHO recommended limit (5 μg/m3, i.e. 0.005 mg/m3) to 432x.

[0] https://content.tfl.gov.uk/dust-monitoring-lu-stations.pdf

The linked article touches on this. It explains that the new trains emit similar heat levels to older trains, and says there was no option to emit more heat without heating the tunnels. They made the running gear cooler (by installing less of it), and using that heat saving as the budget for the air cooling.

As a software engineer who's not touched hardware design in 25 years, I found this heat budgeting really interesting.

If you're the kind of person who plays video games, you might enjoy Oxygen Not Included, managing heat is one of the game mechanics

With the convenience of thermodynamically impossible heat deletion mechanics though. Steam turbines in that game delete heat for every bit of energy they produce.

As is oxygen and waste; I never thought of it as an analog to the same problems that the tube has.

same problems as life on planet Earth!

Tunnels - sure, that's a challenge.

But stations - that's a cost. Stations are connected to the surface by multiple shafts, or are already exposed.

Cooling the stations is not an engineering challenge. It's a budget challenge. Installing and operating huge chillers is a solved problem.

> Cooling the stations is not an engineering challenge. Installing and operating huge chillers is a solved problem.

Not correct in context. You cannot successfully chill air without having a place to vent the resulting waste heat.

Where, in deep tube lines, to vent the waste heat, is _not_ a solved problem. It _is_ an unsolved engineering challenge.

The heat has been accumulating there for decades.

As detailed here

https://en.wikipedia.org/wiki/London_Underground_cooling

https://news.ycombinator.com/item?id=38364027

https://news.ycombinator.com/item?id=38363476

At a certain point it seems like there'd be enough stored energy to justify some heat pumps for nearby building heating.

If that was easy, it would have happened already

https://news.ycombinator.com/item?id=38367176

New Elizabeth Line's trains are quite pleasant though. Not sure if the stations have any better ventilation than e.g. Northern Line.

...especially with such cramped stations and tunnels as the London tube!

I found it very funny to see these trains parked behind my house. I live in Vienna, but apparently some were assembled here.

Scale factors in assembly are very important for both quality and low costs, so a few assembly lines around the world make sense for trains. Then ship them to where needed. I'm not sure if North America should have assembly lines, but politics means we do. Of course if the US ordered a lot of trains this would change, but a lot means that a line needs to be turning out several completed trains of this size per hour (it would be nice if world public transit was that popular)

US does have assembly lines... You may underestimate the number of trains and rail cars that US needs.

Just servicing NYC metro and commuter area would easily make a few assembly lines profitable.

the US does have them - but I'm not convinced we should - vs building them in say Germany and putting them on a ship. Yes assembly lines are profitable. However less assembly lines that produce more trains allows for efficiency from scale and thus could potentially be even more profitable while selling trains for less.

NYC does not have a lot of trains. Sure they are in the thousands, but automotive assembly lines can turn out as many cars in a week as the whole US has. Trains also generally last for 40 years (the London trains in question are older than that).

Note that the US has them because of "buy America" rules and not for good reason. Those rules likely increase the costs of trains.

The Piccadilly line is known as The Tandoor in some parts of London, hopefully no more!

It's got nothing on the Central Heating Line.

Red to reflect the fact that it is actually Hell.

Not 100% sure I get it, I assume because it gets very hot and I guess, has a strong odor?

It's really hot, you get plastered to the inside of the doors when it's busy and goes through Hounslow which is where the Indian population is in London. They named it that themselves and it caught on.

I lived in Hounslow for thirty years and got the Piccadilly Line daily. I never once heard it referred to as The Tandoor.

Living in zone 6 where the underground is overground, it’s more like Jalfrezi at this time of year.

Lived there for 20 years and heard it regularly. Did you have headphones on for 30 years on it? :)

No. And a quick search finds possibly one mention of it from 9 years ago on Reddit. It's not widely used.

> and goes through Hounslow which is where the Indian population is in London.

According to the 2021 Census, 656,272 Indian British live in London. Hounslow total population is 288,200, 21% of them Indian or around 60,000.

British Indians are the second largest ethnic group in Hounslow (after "white"), but there are almost 600,000 more living in other parts of London.

https://www.ons.gov.uk/census https://stats.hounslow.gov.uk/population/#/view-report/63aed...

It's like an oven, there's not much more to it than that.

The biggest question I have is why does it take 47 years to upgrade trains in one of the richest cities in one of the richest countries in the world?

Haven't you seen 'Yes, Minister'?

But in all seriousness I can't imagine all the layers of un-elected, unaccountable bureaucratic petty power centres a mere elected official would have to navigate to get anything done in London.

It's the same in all westminster democracies - I'm from New Zealand and it's projected to take 10 years to make a 3.5km/2.2mi underground rail tunnel in our largest city. Let's be optimistic and say it's only 4 years late - that'd be a bit over half a yard/metre of tunnel per day.

I wonder if future tube lines could have some sort of cooling system to pump heat into some underground reservoir in summer which could then be the source for a district heating system above ground in winter.

I'm just wondering about how to make the problem a benefit.

They do use the excess heat for some public buildings in Islington https://www.islington.media/news/bunhill-2-launch-pr

I never knew this existed before and can't help thinking it's absolutely incredible. Thanks for sharing!

The ground around the deep tunnels already is a heat reservoir, over decades it heated up. https://en.wikipedia.org/wiki/London_Underground_cooling

That is interesting because it suggests that we could grab some of that heat in winter and pump it into houses and businesses on the surface. In the long term that would help summer heat in the tube to be less of a problem.

The idea of "Grab that heat and pump it into businesses and apartment blocks above" requires actual physical infrastructure, and so suffers from the same issues as drilling new ventilation shafts to simply vent waste hot air into the air above: It's a densely inhabited area, and has been for a long time. It is neither cheap nor easy to find room for those ventilation shafts, both below and above ground.

If venting was easy, it would have been done long ago, well before the idea of re-using waste heat rather than just venting it was a thing.

They don't have to vent air though, for the same reasons we don't need to vent air for geothermal heat pumps. It doesn't seem all that crazy to drill minimally for some coolant lines and run a mini-split style heat pump system into the hottest stations.

I'm not saying this is easy per se, but far from impossible, or impossibly expensive.

This has been done to some degree at Green Park station, which still very much is quite warm in places, for ~£9M about a decade ago.

But when TfL has had its budget slashed, and such projects are competing for financing with other projects with more direct operational benefit… it's hard to justify. And it's still not necessarily easy to drill at all!

Agreed that drilling isn't easy, but this does seem more like a budgetary and political issue than an engineering challenge.

Not much (if any) drilling may even be necessary, as there's also the option of running coolant lines directly into the train tunnels. Existing water infrastructure could also be used as coolant — especially if it's otherwise sitting idle for a fire that hopefully never happens!

> seem more like a budgetary and political issue than an engineering challenge.

Science is about proving that something can be done at all.

Engineering is about taking that result and productionising it - doing it reliably, safely, effectively and on a budget. On the right site, even if that's in a busy city. "time and budget issues" are part of any engineering challenge. Very few engineering projects are "Money no object".

An also, there currently isn't the political will in the UK to invest in expensive infrastructure and engineering projects. London actually gets more investment than the hinterlands. See https://www.reuters.com/world/uk/whats-happening-hs2-britain...

It seems like we're in agreement here? Geothermal heat pumps aren't particularly novel, so it doesn't seem like engineering a solution is the blocker here. It's mainly politics.

Exactly, budget is an engineering concern, and in this case it's nigh impossible to engineer a solution, given the space and budgetary constraints.

The budgetary constraints are purely political though. Stuff like this has been engineered before at a reasonable cost (eg the Green Park station for 9M according to a poster above). So while yes things have to be engineered to a cost, it’s clearly not some impossibility high number.

It would need to be made so that it uses more heat than needs to be disposed of throughout the year though. Plus, digging heat pumps like that is a huge and complicated undertaking, with all the existing underground infrastructure.

I read half way through that article and I still don't understand how did they manage to fit aircon on these trains. There were various ideas over the years including for the trains to carry ice, but none stuck.

This time they finally develop ac "that doesn't emit heat outside" and they say nothing about how it works?

If I understand correctly, it is not about "not emitting heat", they reduced the natural output of heat of the trains and gave the excess allowance to the new AC system.

I wonder, are we now at equilibrium with the surrounding earth so the heat of the trains is now actually vented outside, or is the clay still absorbing heat?

If it's the latter than this merely kicks the can down the road and ambient temperatures will keep rising.

The article is not quite explicit about that, but it does say "cooler running trains could help to cool the tunnels, but it would take decades to notice the difference, or they can use that temperature gap between the new and old trains to put air conditioning inside the carriages today... If a future plan to run even more trains through the tunnels goes ahead, that will require increased cooling in the stations, which, funding permitting, is being developed at the moment."

The implication seems to be that an equilibrium (or something very close to it) has been reached for the current traffic volume (and putting aside climate change, presumably.)

The earth is naturally at equilibrium with the average air temperature outside. (when you get really deep the earth's core makes a difference, but at these depths we can ignore that). However when you add heat like the tube does, the earth is enough insulation that it can be decades before it reaches equilibrium again. For purposes of this discussion clay should be seen only for the R-value. (absorbing heat is a very useful property of clay for other purposes, but in this discussion that is not relevant)

According to https://en.wikipedia.org/wiki/New_Tube_for_London, "energy consumption 20 per cent lower than existing trains due to regenerative brakes, LED lighting and lighter construction"

...and apparently they managed the "lighter construction" mostly by reducing the number of bogies? According to https://en.wikipedia.org/wiki/London_Underground_1973_Stock, current Piccadilly line trains have two 3-car units, which means 2x3x2 = 12 bogies. If you look at the video, the new train seems to be just one unit with 5 "actual" cars (with bogies) and 4 bogie-less segments suspended in between, which means just 10 bogies. Also, the new trains are 7 meters longer than the old ones.

As an American that has been to Europe several times, I would say "not emitting heat" is an accurate description of AC in western Europe in general. I'll never forget driving with a friend in Germany when it was about 85 degrees outside and they set the AC to 78 with low fan speed. I'm not trying to throw shade, I just wish I could be happy with that amount of cooling. I would have turned it down to 68 and blasted the fans (when I'm sweating, I want my AC to feel like I just entered a walk-in fridge loaded with box fans). I suppose it explains why Americans have such a huge energy footprint.

If I travel from Northern Europe to hot places, the first thing I have to do in the hotel room is turn the temperature up about 5-10°C.

If it's 30°C outside, 25°C is a reasonable room temperature. I don't want a shocking transition when I go in and out.

Last year I visited a place with almost 40°C outdoor temperatures, and I set the car AC to 28-30°C.

I'm an American, and I typically don't use the AC in a car unless it's above about 90 degrees, I just open the windows.

Is there a reason why? If it's fuel efficiency the AC is far more efficient than the drag open windows adds. Fresh (ish given you're on a road) air I kind of get but at anything other than city speeds the noise gets unpleasant fast for me.

Yeah I just prefer fresh air (even knowing that newer cars with in-cabin air filters probably have cleaner air than outside). If I'm sitting in city traffic and not moving much, I do use the AC more.

That's fair. I grew up in the midwest where it gets pretty humid in the summers. Even when it's in the 70's, driving with your window open doesn't help with feeling gross and sticky.

Why do they continue to use fabric for the seats?

Fabric and foam gets insanely dirty and is almost impossible to properly clean.

There's also the very real problem of bedbugs being spread via the tube.

Hong Kong MTR does it well, metal seats, easy to clean

Still unclear why they didn't go for first replacing Central/Bakerloo triains

Central Line is due next ~2030. Then Bakerloo: ~2033.

It's kind of reasonable to deprioritise the Bakerloo, even as someone who used to use the Bakerloo very frequently. Bakerloo gets significantly less usage than other lines: Piccadilly has double the number of annual travellers than the Bakerloo, for instance.

(It'll be interesting to see if Piccadilly usage numbers go down now Crossrail has been finished and some portion of Heathrow travellers switch over.)

The Bakerloo itself is also kind of a weird, redundant line. The NW segment doubles up with the Watford DC line, and for a lot of NW destinations like Wembley, the Jubilee and Metropolitan are better choices.

There was also the issue of the proposed extension out to New Cross and/or Lewisham. They probably wanted to put off making a decision on the rolling stock upgrade until after they'd decided whether they were doing the SE extension.

In my exerpience, whatever traffic the Elisabeth line has diverted hasn't made a difference. Piccadilly line still busy - I live on it.

Hasn't Crossrail also diverted many travellers from the Central line?

Warwick Avenue and Maida Vale are two important stations to the Bakerloo line in my opinion

Central Line trains are 20 years newer, so presumably aren't going to be at the front of the queue. They do seem to be planning to do major refurbishment / upgrades on them in the near future, up to replacing the motors and related power control systems (DC to AC motors).

Bakerloo line trains are about the same age of the Picadilly line, but the Bakerloo line is less used, so presumably that has edged the Picadilly ahead. They are next in line, as the article notes.

Yeh the central line is AWFUL. I used to travel out of my way to avoid it.

I feel sorry for the people that have to use it to commute every day. Surely their hearing must be being damaged.

I agree. I prefer to use the Elizabeth line whenever possible.

Wasn't taking traffic off the central line a motivation from the start for Cross rail? This might be another reason why TFL is prioritising other lines over the central.

Doing five minutes research it seems that it's just down to the Piccadilly line being busier than the Bakerloo line - given that the Bakerloo being duplicated in parts by the London Overground.

The Central line are on much more modern stock - the 1992 stock, and are currently undergoing a renovation programme, so the need to replace them is less pressing.

https://www.ianvisits.co.uk/articles/look-out-on-the-central...

coming soon

Those are just refurbished current stock I believe, so likely will still have no air con.

Probably because the NTfL studies forecasted much larger opportunities on Piccadilly (60% capacity increase versus 25 on central and bakerloo). So they prioritised deploying the new trains on Piccadilly.

All three lines, and Waterloo & City, are planned for upgrade.

Finance I guess.

They’re working through a process of rebuilding Central line trains, updating virtually everything it seems.

The real issue is the excess heat from losses (breaking, mechanical etc.) [1].

This heats the stone of the tunnels since the tube was built. The heat can't dissipate fast enough. The tunnels get hotter every year.

Because of this the tube has gone from a cool place you escape to in summer, in the early 19th century, to a place you'd look for warmth in winter. And a sauna in summer.

Any air-conditioning system that produces excess heat as a side effect will make this worse.

Even if the passengers on those trains will feel it less.

[1] https://www.wikipedia.org/wiki/London_Underground_cooling

They took some heat sources away by switching to regenerative braking and moving to LED lights so the AC has some head room to play with for not introducing more heat. These trains are supposed to run cooler overall than the ones they're replacing taken as a whole including the new AC.

Can't this be regarded as an opportunity instead of a problem? Sink a few shafts and use heat pumps to extract the heat to a district heating system.

If it was logistically easy to sink air shafts, it would have been done a long time ago, just to vent hot air, long before also using that heat was an idea.

It's a densely built up area. Space above and below ground is hard to find.

I wonder if they could bore some geothermal loops to move the heat someplace else to dissipate more easily.

Being done. https://www.ianvisits.co.uk/articles/cooling-the-tube-engine... (from 2017, 59 HN comments from 2022 at https://news.ycombinator.com/item?id=31694445) says

> Elsewhere, they’ve been using cool groundwater to cool some of the stations. An experiment at Victoria station was the first, as water from the River Tyburn was used to cool the air in the station. This was only an experiment, but at Green Park, a permanent version was installed in 2012.

> There, five boreholes were drilled deep down into the ground, and here cool water is sucked up to the surface, used to cool a separate water supply which is pumped down to cool the platforms, and the warmed groundwater is also pumped back into the ground.

Here's Geoff Marshall's take on the new trains:

https://www.youtube.com/watch?v=mlP9cJOHEEc

Was the subject of a classic Monty Python bit in one of their books in the 70's.

https://greatwen.com/2012/11/20/how-to-take-your-appendix-ou...

But wouldn't this make the problem even worse? Air conditioning will dump even more heat into the tunnels.

Given that the trains stop at the platforms within quite a small area, I wonder if they could store that heat between stations and then dump it into a sort of extractor which takes it to the surface (or uses it to heat buildings, etc.)

That would be very complex and expensive.

Technically, you could just pump out hot water and pump in some cold water, on every station.

But achieving reliable coupling between the train and any kind of piping system would be complex. Remember, there is electricity involved already and you don't want to mix leaking pipes and electricity.

When you realise you have to do something very reliably on every train stop, on every car a more passive solution like piping cold water through the rock might be cheaper long term.

I was just thinking about something like this.

I'm not sure you'd actually need to have physical coupling from the train to the platform. Train lavatories used to just dump their contents out of the track. Given that tube trains are already required to stop at a very precise location on the platform, perhaps the hot water could just be dumped into a funnel built into the ground underneath the track beneath the rails.

Getting cold water onto the train would be harder. Perhaps a big funnel on the top of the train underneath a pipe? ;)

For the cold water, fill them on top like a steam train!

See the 10th paragraph of the article.

For those who won't bother to RTFA: the trains run cooler than other trains, so they are taking advantage of the difference such that the net result is the same temperature in tunnels, but the interior of trains can be cooler.

Oh, so this is exactly like budgeting. It does not matter a lot how much something costs, what matters is where the money came from.

Here we improve the trains to emit less heat and immediately spend it on air conditioning.

In the meantime the debt (tunnel excess heat) continues to rise and somebody else in the future will have to pay for it.

It's more like budgeting at a home level, in that you have a set limit of heat that you can spend, and choosing to spend it less on equipment like brakes, traction motors, etc. and more on air conditioning means still remaining in budget.

Their overall limit of heat output by the trains remains the same. The tunnels won't be any hotter than they are now, thanks to savings found in other systems.

No, it is more like government spending. It is like saying, "we need to be fiscally responsible and that means only spending no more than 160% of what we are earning".

The tunnels are getting hotter and hotter. Saying "the tunnels won't be any hotter" is completely unfounded in reality.

Reading a bit more into this, I'm still not sure whether the tunnels are actually continuing to meaningfully increase absent external changes to the system. Is it at a steady-state heat flux between the inputs (passenger, vehicles, infra) and output (into the surrounding earth), or is the surrounding earth still not effectively saturated?

I know heat inside the tunnels fluctuates with time of year, but I can't tell if year-on-year the tunnels are getting e.g. 1xx% hotter and, critically, what the causes are (more tph will obviously, global warming will, more pax will).

I love how British articles have no problem using words like "Moquette" Does everyone in Great Britain know the definition?

https://en.wikipedia.org/wiki/Moquette

No, but anyone who has used the tube or busses more than a couple of times will know exactly what they're talking about when they see the pictures of the seats associated with the word.

Check out Geoff Marshall's video with a real life Tube moquette designer (Paul Marchant):

https://www.youtube.com/watch?v=cAJrfL6loC8

I can't remember a time when I didn't know the word, but then I grew up near London so used the Tube regularly as a child.

It's that disgusting fabric found on the Tube that when you slap it, you can see a plume of dust and god knows what else

A video tour: https://www.youtube.com/watch?v=mlP9cJOHEEc

Does anyone understand the multi-gauge track in the picture titled:

"An unusual view from the front of a Piccadilly line train"

it seems pretty fascinating.

The other rails are the electric supply, 19th century style.

If anyone from TFL is reading this, for the love of God please do the Victoria line next.

I'd far prefer them to do something about the ungodly flange squeal - TfL, grind your tracks!!! That's way more of a clear and present health risk to me than the heat.

I hate to break it to you but Victoria line modernisation, including cooler trains, has already happened in 2009. Here's an example IanVisits article about that:

https://www.ianvisits.co.uk/articles/today-marks-the-final-t...

And you can tell. The Victoria line is way more comfortable than the three lines getting an upgrade that are all hellish, all your round.

It’s nice to be able to go to Cockfosters in comfort.

Carpet never belongs on city trains. How does this keep happening?

Where are you seeing carpet? Looks like vinyl or linoleum to me. Or do you mean the upholstery?

Will it get any quieter, though? And why can't we get rid of the moquette, they get disgusting quickly.

air conditioned trains are an achivement in 2023?

I don’t know if you’ve been to london, but if you’re a standard “modern” height for a man you can barely to not even stand straight in the deep tube trains. They are very very small, and limited by the tunnels which are absolutely tiny. I’m not surprised fitting air conditioning is a challenge, even ignoring the ventilation issues which are also massive.

a consequence of having the first subway in the world i think.

Yep, same as many other things we take for granted in modern constructions, such as accessibility, good signage, enough space on stations and tunnels for easy flow of passengers, platform screen doors, etc.

It's a no brainer when building today, but wasn't back then, and retrofitting is extremely complex and expensive.

Dug "by hand": https://hornseyhistorical.org.uk/piccadilly-line-extension-p... https://en.wikipedia.org/wiki/Tunnelling_shield#Manual_shiel...

You should see the Glasgow Subway - its trains are almost comically small.

The entire network is a single line which circles the city, the map shows 2 lines, one clockwise, one anticlockwise. The trains have a dirty orange livery, hence the local name: The Clockwork Orange.

My favourite underground in the UK.

It's a huge achievement considering both the technical challenges (which other comments explain) but also that anything actually got done considering the UK's economic and political disaster.

Well fortunately New Tube for London (this new train design) all got signed-off a decade ago. Buuuuuut, TFL only bought the trains necessary for the Piccadilly line, with "options" to buy trains later for the other lines. However, post-Covid they don't have enough money to buy them anymore, and would need the government to pay for them, which it likely won't. So I won't be holding my breath for any further improvements :-(

> UK's economic and political disaster.

i really don’t understand where this myth is coming from. do people seriously think the UK is an “economic disaster”?

https://data.worldbank.org/?locations=DE-GB-FR

and here are the numbers for 2023: https://commonslibrary.parliament.uk/research-briefings/sn02...

I don't think it's a myth. The UK is actually two economies. It's basically southern Italy with NYC bolted onto it. The average numbers like those you've posted include London and look basically OK, but the London effect is hiding a lot.

Take out London and the rest of the UK is an economic basket case with low education levels, high rents, rapidly aging citizens, low wages, low investment, low productivity, a small tax base and a public estate in poor condition.

This was a really interesting piece on the matter, in fact most of Murdoch's work for the FT is excellent

https://www.ft.com/content/e5c741a7-befa-4d49-a819-f1b0510a9...

If you don't have a way to access the FT, this chart encapsulates my point quite well

https://www.ft.com/__origami/service/image/v2/images/raw/ftc...

London itself is very divided. There's plenty of money in a few select areas, but wastelands of poverty around them.

The UK has a huge reservoir of natural talent which it's doing its best to destroy. Plastic populism suits the ruling class much better than invention and originality.

> There's plenty of money in a few select areas, but wastelands of poverty around them

You can find the wealth and the poverty very close by, even at the same London address. i.e. a flats with huge book value, privately owned; and rented out to struggling people who will never be able to afford to buy their own flat.

> It's basically southern Italy with NYC bolted onto it.

More like "basically Romania with Vlad Tepes bolted onto it". The London-driven finance-first economy (to which I partake, btw) inevitably sucks the blood out of the rest of the country.

To be fair London is 13% of the UK's population, whereas Munich is a little under 2% of Germany's, I'm not surprised Germany's output stays the same!

https://en.wikipedia.org/wiki/2021%E2%80%93present_United_Ki...

> but also that anything actually got done considering the UK's economic and political disaster.

It's London...

Here in Hamburg the S-Bahns are only just being replaced by air conditioned models. I don't think there are even plans for an air conditioned U-Bahn yet

It's best to read the article to understand why.

Where would the waste heat go? Air Conditioning units dump the heat "outside" into the air. But there is no "outside" in deep tunnels. Worse, Air Con has to work to move heat, which creates more heat. You can't even break even. See the 2nd law of Thermodynamics.(1)

It's not so much "air con on trains" but "air con in deep tunnels without a vent". There is nowhere for the heat to go, and the tunnels have already warned up over the decades. (2)

> Conventional air conditioning was initially ruled out on the deep lines because of the lack of space for equipment on trains and the problems of dispersing the waste heat these would generate.

Every solution is a costly compromise. e.g. drilling a new vent to the surface is theoretically possible, but very hard in a densely populated and built-up area.

A lot of comments talk about tunnel size, which is a minor factor: Everything's easier to engineer when you have more space. But fundamentally the issue is where to send the waste heat, not "tunnel too small".

1) https://en.wikipedia.org/wiki/Laws_of_thermodynamics

2) https://en.wikipedia.org/wiki/London_Underground_cooling

Couldn’t they make some spaces, and a drain and bring in large blocks of ice to take heat out?

I’m guessing water would be creating more problems. But it’s a train line, bringing in large blocks of ice should be simple.

Air conditioning in a busy 19th century underground tunnel system is absolutely an achievement.

Air conditioning an underground train means pumping that hot air into the tunnels. The tunnels have insufficient ventilation because this wasn't conceived of as a problem when many of them were built, and that's a challenge to rectify.

There's also the issue that the trains are already making the tunnels too hot. 4000 trains running back and forth generates a lot of heat from both the engines and braking friction. That heat goes into the clay of the tunnel and is very slow to dissipate due to the high heat capacity of the clay. The trains are never stopped for long enough for the temperature to drop, and so the temperature of the clay has slowly risen 5-12 degrees depending on the line from when the first line was dug in 1863.

Air conditioning the carriages of the new trains didn't result from any developments in air conditioning technology, but from breakthroughs reducing the thermal output of the engines and brakes. This gives them a heat "budget" letting them air condition the carriages without outputting any more heat into the tunnels than a standard train.

Yes, given the size constraints of the deep-level Tube tunnels, which are much smaller than those for mainline trains; apparently developments in small air con systems have helped a fair bit here, fifteen odd years ago apparently it just wasn’t feasible.

Arguable the more fundamental problem is this. Air-con is a negative-sum game because it not 100% efficient. As well as moving heat from one place to another, it creates extra heat.

Turn air-con on in an enclosed space, with nowhere to vent the exhaust, and that space just gets hotter. A small, deep tunnel is close to being an enclosed space. You might be able cool the train interior a bit, but the tunnel will get hotter. Meaning the air-con has to work harder. Meaning it generates more heat.

The Picadilly line is already uncomfortably hot for a good part of the year (but far from the worst [1]). This includes the platforms.

What this article says is that the trains themselves are lighter and more efficient, so less heat is generated by the motors and brakes. They argue that that gives them some heat budget to use on air-conditioning. As a whole, the new trains will generate roughly the same amount of heat as the old ones. So the tunnels and platforms will stay around the same (ie, too hot!), but the train interior will be comfortable.

[1] https://www.standard.co.uk/news/london/tube-underground-lond...

Yes, "Where to vent the waste heat" is 100% the fundamental problem. You can't beat the second law of thermodynamics.

The tunnels have absorbed heat over the decades, venting yet more heat into the tunnels is not going to work.

More space would make the engineering easier, but it's not the fundamental issue.

Adding AC units to trains which travel through tunnels with minimal clearance is the achievement - Can't make the trains any bigger and there's no room in the old ones to just tuck an HVAC in without make them even more cramped.

AC units dump the heat "outside" into the air. There is no outside in deep tunnels. Nowhere for the heat to go. The tunnels have already heated up over the decades. https://en.wikipedia.org/wiki/London_Underground_cooling

It's not primarily about headroom.

Headroom is not an issue - there is plenty of room underneath the trains between the wheels. They then pump the cooled air up through the walls to where they want vents. Sometimes trains use the space between the wheels for passengers, but that has significant disadvantages and so should be avoided for subways (it is worth it for street running trams!),

It is here; they're small trains and the tunnels are very warm already, so the AC isn't as efficient, and adding more heat to the tunnels (which all comes from the running trains) will make it more inhospitable.

There are some projects underway to try and cool the tunnels, but they're deep underground and have accumulated heat over decades.

Air conditioning a train in a tunnel is a trick, because the tunnels heat up and can’t dissipate heat well at all.

The challenge here is specific to this line - other lines (like Circle) already have AC on the trains - mainly because they’re absolutely huge trains by comparison

London 2 main types of underground line: Subsurface (Circle, District, Metropolitan and Hammersmith and City lines), and tube. The subsurface lines were constructed by cut and cover and were made for steam engines. They are much larger than the tube lines. The Tube lines are tunnelled, and designed for electric power only.

It's not really the size of the trains that allows AC on the subsurface lines, it the fact that the lines are well ventilated to allow steam and smoke from steam engines to escape.

Even the article specifically points out the size of the train as an issue

> To fit air conditioning into the trains has been rather an interesting challenge, as air conditioning units are large and tube trains are small, and Siemens Mobility has taken several ideas and put them together to create the space needed.

London underground runs in a parallel universe where they are reinventing 60's tech.

They only recently got cell service for example. 20 years after most of the rest of the worlds railways.

Some lines don't even have that yet either!

Of all the things TFL could do to improve the tube, cell service would not even be close to top of my list. We've had WiFi on the platforms for about 10 years which is enough to send/receive whatsapp messages while the train is stopped.

I'm not sure it's fair to dig out TFL for being backwards. They introduced the Oyster in 2003, something NYC didn't get until 2019.

That Wi-Fi is unusable. Not only does the association & DHCP negotiation take a large part of the time the train spends stopped at the station, but there's a stupid captive portal that also wastes whatever valuable time & bandwidth you manage to get despite the other issues.

I've been travelling to places where conventional mobile service is available in the subway and it's such an improvement. Being able to look at maps, message or browse the net is a godsend especially as a tourist in a foreign country.

Just having accurate next-train-arrival boards on each platform is a huge win, and not something every other subway system seems to have.

Reliable comms everywhere allows fully centralized train control, with no employees on each train. You can use cameras to check no passengers are stuck in doors, on the track, or fighting in the carriages or platforms.

Now you can redeploy the staff away from repetitive tasks of driving trains and supervising stations, and towards engineering a better service. Get the typical journey speed up from 12 mph up to 45 mph. Make one direction of all tracks an express route that only stops at one station in 10 and drives 60 mph through all the others. Modify the old tunnels with an extra rail on a wall or ceiling for places where the tunnel alignment can't do 60 mph.

Are you a railway engineer or in some other related field?

Some of these suggestions sound a bit bizarre to a layman, especially considering your idea that the only thing standing in our way is 4G signal and reshuffling some staff.

> Get the typical journey speed up from 12 mph up to 45 mph.

So instead of 30 minutes from Walthamstow to Brixton it'll be 8 minutes? How is that possible?

There are 16 stations, or 14 stops excluding the terminii. If you stop for 30secs at each, that's 7 minutes in itself.

> Make one direction of all tracks an express route that only stops at one station in 10 and drives 60 mph through all the others

So we would have an express lane in one direction and a stopping lane in the other? Why is that a good thing?

To me an express service seems /slower/ than the status quo, because I would have to wait longer for the train that stops where I want it to.

> So instead of 30 minutes from Walthamstow to Brixton it'll be 8 minutes? How is that possible?

> There are 16 stations, or 14 stops excluding the terminii. If you stop for 30secs at each, that's 7 minutes in itself.

Or... you could stop at only 6 of the stops (express service). You could stop for 15 seconds door-open-time (as long as the crowd waiting for the train entirely fits on the train, thats very achievable - and crowd control can be managed by controlling platform ingress). Busses often achieve 3 seconds of door open time for comparison.

At a top speed of 60 mph, max acceleration of 0.2g, max jerk of 3 m/s^3 and travel distance of 2 miles per stop, the whole travel time becomes 13 minutes. Plus the 1.5 minutes for stops. =14.5 mins = 49 mph.

Lets schedule in one 30 second slowdown (ie. drunk guy holds door for mate for 30 seconds), and the average speed hits the 45 mph target.

I suspect the victoria line, being more modern in its track alignment, could easily be made to go 100 mph too...

How do the express trains get around the slower stopping trains? Or are you going to entirely remove two thirds of the stops?! I don't think you'll have any risk of crowded platforms, it'll be far too useless a service to attract many passengers.

You cannot compare bus stopping times with tube stopping times. It's meaningless. But if you must, the average dwell time for a London bus is closer to 15 seconds. Which is actually quite remarkable when you consider you've got to pay as you get on. And there's often a buggy or two trying to negotiate the driver having parked too far from the curb. The peak and off-peak must be wildly different and make this single measurement pretty useless.

https://clondoner92.blogspot.com/2022/07/tfl-publishes-avera...

Ok, so your big plan for quadrupling the speed of the tube is for trains to breeze through most stations without stopping. It's like amputation as a weight-loss tactic.

Simulate it and see... The vast majority of journeys become quicker, even though many trains don't stop at many stations.

The optimal strategy is probably to have multiple express routes - ie. Train 1 stops at station A, C, E, and train 2 stops at B, D, and F. A better signalling system becomes necessary for that though - moving block signalling isn't sufficient - you need one that can take into account velocity-acceleration-jerk of both trains to get trains close enough while still ensuring passenger safety. That in turn requires Comms systems not just train presence information.

> So we would have an express lane in one direction and a stopping lane in the other? Why is that a good thing?

Simulate it and see...

Turns out that despite most users needing to make more changes, they will complete their journey far faster. The few journeys that are not completed faster (eg. taking the tube one stop) tend to either be walking distance or have an equivalent bus.

Combine it with the fact there are multiple routes from A to B and there are many people who can take the fast train in both directions.

For the railway operator, the trains are a big capital and operational cost. If you can make the trains run faster, you can get better utilisation of the seats, and therefore extra capacity/revenue. That more than outweighs the extra maintenance and electricity costs of going faster.

the london tube dates from 1863. that explains most issues.

The slight problem there is none of the rest of the world's railways are in London.

That's a feature not a bug.

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