What About The London Underground Makes It Uniquely Primitive?

Inspired by the story of the Tube train derailing this morning:

  1. Read a story a couple of months ago in which the director of the Underground explained how super-difficult it was to come up with a feasible air-conditioning system (this in the context of a somewhat-flaky plan to put ice blocks under the seats and blow air over them), because “you have to understand that it’s an underground tube and you need some way to exhaust the heat.” Well, that’s true of every air-conditioning/refrigeration system, or more specifically, of every subway air conditioner, yet other subway systems seem to manage and find ways to vent/exhaust the hot air. (They were also talking about diverting water from the Thames into underground chambers to serve as a heat sink).

  2. Read another story in which they said that “of course” they would never be able to run the Tube 24 hours a day “because it’s a single track system.” I’m not sure exactly what this means or how it fundamentally differs from, say, New York.

I do know the tubes/trains are comparatively narrow, which I’d assume makes it hard to run additional utility pipes, etc. Anything else?

The London Underground (which is not a political movement) was one of the first (and may have been the first) subway system. It’s also one of the deepest (one reason it could be used for bomb shelters – the Paris Metro, for instance, was too shallow). It was cut through the rock and I don’t think there’s a lot of extra space.

Places like Paris or New York are close to the surface, so it isn’t hard to run an exhaust for hot air. London is much deeper. Other deep subways (like Washington DC) were built with air conditioning in mind.

Most of New York is four tracks (two local and two express). I believe it is possible to route a train from the local to the express track (and vice versa) in order to shut down one line for repair.

London was the first, unless you count the one-block-long pneumatic subway built in New York (but killed by Tweed and his cronies, who had an interest in maintaining the El). London had the first operating subway, followed shortly thereafter y Boston and Patris. New York didn’t get theirs until later.

This page might give you an idea of the restrictive conditions under which the London Underground operates. Especially note the two photos - the first will give a good idea of how little clearance there is between the train and the tunnel, and the second will show you exactly how tiny those trains can be (the “big” train used as a comparison is still relatively small, simply because it is British and therefore built to the small British loading gauge*).

*Loading gauge is nothing to do with the distance between the rails. It is the maximum allowed height and width (and sometimes length, depending on curves) of rolling stock, dictated by the proximity of bridges, tunnels, and other lineside structures.

I don’t think that the tube cuts through rock. The reason it was originally called “the tube” is that it was an actual iron tube through which the trains run rather than just a hollowed out space. The reason for the iron tube was that the soft earth was not able to hold its shape on its own when hollowed out. This is from memory of an old history of subways.

Mind the gap!

I love the song, London Underground. The lyrics (NSFW) are found here, as well as a link to download:

The key to these is that, for the most part, the London tube is, in fact, a tube (or rather, many tubes). To build most of the Underground, they hollowed out circular tubes under London with boring machines, through which they ran tracks and trains. As a consequence, most lines are a single “tube” in each direction, without a lot of track switches or cross-overs underground. There are also few track connections by which trains from one line may be rerouted to another. In addition, many of the tubes are very deep underground (enabling their use as bomb shelters during the London Blitz, among other things).

In contrast, most of the New York City subway was built by “cut and cover”, digging down from the streets , excavating a large trench, and covering the excavation with a roof that becomes the street above. A significant portion of the system is built with four parallel tracks, one local and one express in each direction (sometimes three tracks, with one reversible express track in the middle). There are quite a few points where trains from one line may be diverted to another to avoid a section of track being worked on.

On the air conditioning question, what you have is a bunch of tubes cut deep into the soil under London, only connected to the surface by the exit stairwells/escalators. There was no provision for air exchange when the tube was built, and there is a real problem with getting the hot air out and cool air in. Note that the New York subway is not air conditioned, though most stations and large portions of the track are vented directly to the streets overhead.

On the 24 hour question, to maintain a particular line, they would essentially have to shut down the whole line to do maintenance. In New York, they have daily work trains that, for instance, go station to station to pick up the garbage. (The famous money train, which picked up fare collections, is no longer, made obsolete by Metrocard vending machines that take credit cards.) When a work train is running, there are enough places where the daily work trains can be switched and diverted so that a reasonable (nightitme) flow of passenger trains can be maintained.

When there is other work to be done on the tracks, it is usually fairly easy to set things so stations can be serviced while one of the tracks is taken out of service. For instance, if there are a local and express track in each direction, for work on the express track, trains can just be diverted to run on the local track. For work on the local track in one direction, say downtown, they will often divert all downtown trains to the express track, but leave the uptown local track in operation, so someone needing a local station but travelling downtown can get on at the local station going uptown and reverse direction at the next express station.

There are other more complex diversions that can be done for sections where there is only one track in each direction. In fairly common situation where there are two alternate routes between stations (e.g. both the A/C and F lines go between West 4th Street in Manhattan and Jay Street in Brooklyn via different routes), they may close one in one direction, with customers on the partially closed line having to take the train in the operating direction and reverse where the lines rejoin. Sometimes, they will close down a segment of track between two stations, run a shuttle back and forth on the other open track, and meet up with trains looping back and forth on the two disconnected ends of the lines.

Of course, sometimes these don’t work, and you get the dreaded “bustitution”, where you climb into the open air and take a bus over the subway route, but these are relatively rare considering the size and complexity of the system.

Because of the way it was built, London just doesn’t have all of these options for diversion, which make 24 hour operation of the system possible.

I remember once hearing a Londoner referred to as a “Gap-Minding Bastard.”

There has to be a point at some point for regular checks of track and equipment, which in the case of the Tube means turning off the power. Doing this for sections of the NY subway is much easier, because a stopping train can be switched over to the fast track or vice versa. A deep level tube system has very few opportunities to change tracks at all.

Another issue with ventilation isn’t the construction of the running tunnels, but also that of the stations, which in the tube is also mainly narrow circular structures. Simply ventilating these at present is hard enough. And adding major extra ventilation structures, even if possible, might be shunned due to the potential for them to act as chimneys in the case of fire? (The tube is very fire-risk-aware, since the Kings Cross fire.)
Having said all this, and the comments above, it’s also true that only a small proportion of the Underground is actually underground. The earliest steam-hauled tracks didn’t use deep-level tubes, and so several lines (District, Metropolitan, Circle, East London) have cut-and-cover tunnels. There’s a completely different difficulty with air-conditioning these, in that they were built with as much ventilation as possible, to allow smoke to escape. Turning them into a true ‘indoor’ air-conditionable environment would be a mammoth task.
Random thought - are there any examples of deep level underground railways which have air conditioning installed, either during construction or retrospectively?

In the time I took to type that, Billdo did far better. When in New York, I do marvel at the forethought of the design of the subway (as well as the seemingly inherent dinginess of many of the stations).

I think it’s a bit of both. A lot of it is run in those iron tubes through London clay. Interestingly, this is why it is run on (the world’s only?) FOUR rail system. Most similar rapid transit systems use a third rail, with the current being returned through the running rails. The didn’t do this in the LU because of concerns the current flow would cause corrosion of the iron tube and also surrounding metal building foundations.

Thank you for that. I have a friend/colleague in London and will use that whence next we speak. :smiley:

Hah, I found this comparison of the tube and the NY subway, on a government website. I like the fact that there will be ‘New trains on Victoria and Jubilee lines by 20102’. It’ll certainly feel primitive by 20101.

I think the main reason for the first uses of deep level tubes was simply that it offered a way to get under the Thames. The earliest deep level railways in London were river crossings. And there’s still road and pedestrian tunnels in use with tubes lined with bricks (Rotherhithe, Greenwich Foot Tunnel, etc. At least I think these ones are brick-lined…)
On further Wikipedia browsing - London Clay is very suited to tubes, unlike the conditions further east, where Brunel had great trouble although the Thames Tunnel survives as part of the East London Line.

Bear in mind that many of the earliest tubes had to go so deep because otherwise they simply would not have been permitted to dig. Only by going deep could they avoid pipes, cemeteries etc and avoid too much disruption to the surface roads.

It can be very uncomfortable if the tunnels are hot and it’s a good idea to try to cool them but personally I’m not sure why so little effort is made to cool the trains as opposed to the tunnels. Passengers will be in a station for maybe ten minutes and will never (hopefully) be out in the tunnels.Yet they might spend an hour or more on a train. Currently we have a rather primitive air-vent system but that does nothing to cool the cars. Yet the driver’s cab has fabulous air-con - today I had it on at the lowest level to provide nice fresh air but had to wear my coat to stop from shivering. And this is from a fairly small air-con unit. It seems feasible to install other units throughout the train which would cool the car to a reasonable degree. Of course that would be affected by opening the doors at stations and allowing warm air into the train/cool air to vent out but it would definitely make a difference.

But Aristotle’s still Belgian, right?

I guess one point is that large scale cooling of train interiors would mean some further heating of tunnels (and hence of stations) if the heat sucked out of the cars were just dumped (as the small amount from the cab probably is) in the ambient air rather than ducted out somewhere.

That’s the biggest problem - cooling the train means pumping extra heat out into the tunnel around it. One small unit for the driver isn’t a problem. Multiply that by God-knows-what, and the space around the train can’t dissipate the heat being created. Especially if you’re stopped at a signal in a tunnel, for instance.

And as a bonus, don’t forget that all this will add a significant load to the electric supply to the trains, and we all know how rigorous and reliable that system is.

I do agree that simply ventilating the trains better might help things somewhat, but on the other hand, 150 bodies is a lot of heat being produced, and if you’re carrying that for half of the morning, the entire body of the car is going to be absorbing that heat.

Yes, and you can still enjoy the Central Line rollercoaster around Bank with the line following the streets for legal & financial reasons rather than engineering ones.
(I can’t believe we’ve avoided Dollis Hill…)

Well, somebody had to.

Those picture/s of the London tubes are frightening. With such little clearance, it doesn’t look like you could get out of the car if there was a fire or just a stoppage of the train.