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Comment by dx034 | Hacker News Reader

Regarding 5, emergency brakes in London won't stop the train in the tunnel. They just send a signal to the driver to wait at the next station and inform staff at that station and/or emergency services.

Pulling the emergency brake therefore isn't necessarily a bad idea. If someone has fallen ill on the train (esp. common in summer), it's the best way to ensure that help will be available as soon as possible.

As you said, evacuating trains in the tunnel is dangerous so it's only done if trains physically can't move to the station (e.g. another train blocks the tracks). And even then, evacuation is only done after electricity has been switched off via the end of the train.

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Maybe you're thinking about the emergency "brake" cord ? That works the same way in NY subways. They alert the driver and conductor to a possible problem in a train car so that they can get police assistance and/or bring the train to a controlled stop.

The emergency brake that is discussed here is different. It's inside the operator's locked cab, and releases air brakes that stop the train with maximal acceleration to the extent that the wheels can be damaged by grinding against the rails. They are only used in a last resort but they have to be available and functional in the event that the human operator finds itself unable to make a controlled stop. The same subsystem activates when the train incorrectly passes a red signal or hits a large obstruction in the tracks.

Thanks. If only there had been a way to divine that from TFA.

I can only imagine transit authorities are being vague on purpose so as not to popularize this particular vector of attack.

TFA explains the break is located an area that should only be accessible to MTA personnel

>He climbs aboard the rear of the train as it departs a station, unlocks the safety chains, somehow gets into the rear cab, and triggers the emergency brakes.

As for pulling the emergency brake for someone who is unwell, there are frequent announcements on the tube telling you not to do that. The advice from TfL is to wait until the next station and help the person get off.

That's true if someone is still able to walk. For people who need medical assistance you need to alert the driver to ensure the train won't continue.

I think they started these announcements because people considered someone feeling dizzy a medical emergency.

I can see that it could be wise to pull the emergency handle at the station to prevent the train moving if, say, someone were having a heart attack and couldn't easily be moved to the platform.

But pulling it between stations would only prolong the time it took for the person to get help.

It won't as there are no emergency brakes on Tubes, they're just called emergency brake. The train continues to the station and will then remain there.

Regardless of whether the emergency handle is connected to a physical brake or if it sounds a alarm, there is an emergency brake. If the driver removes their hand from the dead man's switch, the emergency brake engages. But that's a side-road to this discussion.

Unless you can point to official advice from TfL that states otherwise, I'm just gonna come out and say that I think it's best to stick to the advice TfL give at stations which is not to pull the emergency handle if someone is unwell. Whatever the precise action that results from pulling the handle (whether that's sounding an alarm, engaging a brake, or whatever), I don't see what it would achieve between stations and especially when TfL say not to do it.

There are very limited scenarios where you want to pull the brake; e.g. the door has closes on a passenger and is dragging them along.

But of course these are very limited and you almost never actually want to do that.

In the Stockholm metro there is a intercom to the driver for talking from the wagons. Is there one in London?

Yes, but the audio quality is not very good. There was a recent incident that was exacerbated by a driver mishearing "there's a fire" as "there's a fight".

I find it weird that there's so much confusion about the way emergency brakes work and when to use them on the London Underground. If people on HN can't agree on it, how can the general public? Confusion about this sort of thing can be dangerous.

Part part of the issue is that it changed about 20 years ago. The emergency brakes used to actually apply the brake, rather than signal the driver. But even when I was a lad, there were signs on the trains saying 'if someone is unwell, don't apply the brake until the station - help will get to them faster'.

Makes a lot of sense and is very logical --- that person still has to get off the train somehow, and better at a station which the train is already going to, than to stop and wait somewhere between stations for help to arrive. Perhaps the reason people pull the brake is more of a panic reaction.

That is because people on HN are the general public in a lot of ways. Just because most are specialized knowledge workers doesn't mean they are inherently more intelligent in other areas of life.

Intelligence isn't the right word. There are some sort of jobs that do select for high intelligence. Any sort of work that requires abstract reasoning and novel problem solving is going to be inaccessible to people with lower intelligence.

Rather, it should be said that tech workers are not inherently more knowledgeable in matters unrelating to tech than the general public. In this case, knowledge of train function and etiquette is in question, not intelligence.

(Note also that intelligence does not confer knowledge (although it makes knowledge easier to acquire) and that it's quite easy to find examples of people with modest intelligence but exceptional knowledge. Furthermore the work/intelligence selection process only really applies in one direction; there are a lot of high intelligence people who choose jobs they find undemanding because they have different priorities or have had different opportunities in life.)

Last time I was in a tube when the emergency brake was pulled (not in NY or London), it was by a mom who had left her kid behind at the last station. All it did was stop the tube between two station, the driver had to go check what happened then go back and restart the tube.

The process to reset the brake can easily take 30 minutes or more, delaying 20,000 people or more (all people on the train, plus the trains behind, and the trains which can't start their journey because they're stuck in the wrong place, and the trains which have to be cancelled because it's now the end of the drivers shift).

The real solution is to practice till the time to reset an emergency brake is 1 minute or less. It should be simple - someone in a control room checks all CCTV cameras to see the situation, and presses a button to restart the train.

TFL's cameras mostly aren't digital and can't be watched remotely, so they're miles off ever being able to do this.

At least on certain lines, if you lean on the doors, emergency brakes will be applied, regardless of whether the train is in a tunnel or not.

This often happens when a train is particularly crowded and people are crammed in near the doors.

In deep underground lines? I never experienced that, and in rush hour central line or Northern line it's basically impossible not to lean on the door.

The old district line stock used to do it, but they’ve all been replaced now. It didn’t stop the train it would limit the maximum speed. The driver would keep announcing to stop leaning but in heavy traffic that wasn’t always easy.

I think the Central Line still does it.

I take the central line regularly and this happens once a week. Big yank, followed by a "Please don't lean on the doors, it will slow down the train", it's par for the course.

This slows the train down it doesn’t stop it.

Happens quite often on the Jubilee line, and whether it’s the brakes being applied or motors cutting out, the upshot is the train comes to a very abrupt stop, seemingly with no action from the driver.

This is usually followed by a frustrated driver coming over the PA system to implore people to stop leaning on the doors, because they are unable to move the train until they do so.

Are you sure there aren't emergency brakes in the cab that would stop the train on the tracks?

I'm sure there are but those would be hard to misuse by passengers.

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