Hacker News Reader

Comment by Justsignedup | Hacker News Reader

I don't understand. What possible reason is there for an emergency break...

- If the subway needs to stop via an external decision, there are triggers all over the rails to trigger an emergency break.

- If you are sick, emergency break is actually worse than waiting to get to the next station.

- If anything is happening. Emergency break is wrong.

- If something is in view of the conductor, the conductor will do the correct action.

- If the train is going too fast, there is already a timer and an automated emergency break triggered on the rails.

I cannot think of a single good reason for this. It's like saying there's a "turn engines off" lever on an airplane next to the bathroom.

View on HN

I cannot think of a single good reason for this.

The use case is some sort of emergency that the driver may not have seen.

SF's Muni is in the process of onboarding new trams from Siemens. Someone recently stuck their hand in the doors as they were closing. On pretty much any newish tram or subway vehicle this will cause the doors to open again. It's shitty behavior, but that's what people do. Typically trams in the United States have door interlocks such that if the doors are open the vehicle doesn't move. The new Siemens cars apparently don't have well calibrated pinch sensors and the damn thing took off with some idiot woman stuck in the doors, dragging her down the platform.

I've had similar experiences with the older ones (where the drivers would deliberately disable the interlocks — this was before they put tamper evident bits on the override switch). The driver closed the doors as I was boarding. Without looking at his/her mirrors the driver took off as I had one foot on the street and one on the vehicle.

Same deal with people who've fallen onto the tracks.

With video: https://abc7news.com/video-woman-dragged-by-muni-train-after...

There is absolutely no reason to suddenly stop the train in the middle of a high speed movement between the stations.

Maybe while train still at the station. But not during the movement in the middle of tunnel.

Definitely not relying on random passenger making such decision.

This capability need to be disabled to avoid hurting people. Replace it with the button to communicate with local authorities.

That's what the passenger "brake" in the carriages actually does. The brake in the driver cab is the actual thing being used in this article.

In San Francisco the emergency stop button in the (older) trams will indeed trigger the emergency brakes directly. I'm OK with this — take a look at the Eschede disaster. One of the passengers was suspicious of all the vibration but decided he didn't have the authority to stop the train. Turns out the eventual derailment stopped the train.

Here’s a story: landed in Schipol (AMS) from Berlin with a good friend of mine. Jumped on a train and was half asleep when the train rolled in to the station just before Amsterdam proper. I forget the name.

Just as he train was about to pull off, a man approached us and said something incoherent in Dutch. Before we could even utter our confusion, he grabbed the backpack on my lap and ran for the doors. I followed him but not nearly as fast as I would like. He was jammed between the automatic doors and I caught a glimpse of him yanking himself onto the platform, where he stumbled and started sprinting.

My cries alerted other passengers who immediately pulled the emergency break. The doors opened and we went into hot pursuit.

Sadly, we never did catch the man that day. The backpack had my laptop and many important documents, but by the grace of some Unknown or my own laziness my passport was still in my pocket. In fact when we got to the police station I thought it was in the bag, and their attitude there visibly changed when I was able to produce it. They took a statement and that was that.

So the emergency brake is useful in some situations...never did get that bag back though ;)

Using the emergency brake while the train is still at the platform makes sense. Once the train has left the station, it makes no sense to stop the train.

> the train rolled in to the station just before Amsterdam proper. I forget the name.

Amsterdam Sloterdijk.

Could have also been Lelylaan (both Lelylaan and Sloterdijk are within Amsterdam proper, by the way)

> If something is in view of the conductor, the conductor will do the correct action.

This is the conductor’s control they’re using.

No. This is not. They are using the emergency break lever in every car by either door that is on both ends of the car. It is unlocked and available to all. I once almost pulled it accidentally because the train braked hard and it was so crowded i was holding on to the ceiling.

You need to read the article again then. Although the break pulls you describe are present in every car, the article clearly states that the one being activated is in the unused control cab in the back of the train (the cab used by the conductor when the train travels in the other direction)

The operator cab. The conductors are stationed towards the middle.

I think the one case where it would be good, is if there is somebody stuck in the door and the train starts to move.

Or if the doors won’t close and the train starts to move.

Or the classic: there is a fire in the train and waiting for the next station is not an option.

- if the train is within the station limits, that lever can be active

- in case of fire the lever should alert the conductor. And the conductor should quickly make the best correct response. Often the passengers don't know that a station could be 20 seconds away and could clear out the train faster. The dispatch could clear a path for the train to speed to a better location than stuck in a tunnel with potentially nearly no place to evacuate to. Do you evacuate to ongoing train traffic? hell no! We have fire detectors, we could install them in every cart.

This assumes that when the lever is pulled that the conductor would know why it's being pulled.

Modern subways have interlocks preventing motion while the doors are open, and preventing the doors from opening while the train is in motion.

Modern subways have interlocks preventing motion while the doors are open, and preventing the doors from opening while the train is in motion.

Yeah, until the drivers decide that the doors are so unreliable that it's faster to override the interlocks and hope nobody's caught in the doors (which will eventually reset themselves and close properly).

Usually an interlock is something that can't be overridden, or needs to be done so manually by physically allowing the interlock.

On Muni's older Breda trams the interlock had a little toggle switch on the circuit breaker panel (conveniently located in the cab) you could use to override it. On the newer ones, it looks like the doors didn't detect a "pinch", the interlock decided the doors were closed enough, and the driver couldn't be bothered to check the video cameras.

>It's like saying there's a "turn engines off" lever on an airplane next to the bathroom.

No, it's not, it's like saying there's plane controls in the cockpit. The break is in a cab that should be inaccessible to riders.

>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.

Somebody or something outside getting caught in the doors after they close is probably the most common one.

Reply on news.ycombinator.com