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0 pointsthunfischbrot8y ago0 comments

That, and considering a speed limiter instead of stopping the train when traveling too fast. What good does it do to stop the train when going too fast instead of limiting it in the first place?

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8 comments · 2 top-level

gsnedders8y ago· 6 in thread

The general principle in railway movement authority is that there's an easy fail safe: stop moving. If nothing moves, there can be no collision.

If something goes wrong? Stop the train. You can then figure out what went wrong and address it with no risk. Things shouldn't be going wrong, speeds shouldn't be being exceeded, etc.

ovi2568y ago

>If nothing moves, there can be no collision.

If no train on the line moves, sure. But stoping just the one train won't improve safety, and was historically the cause of many accidents. I remember just the one in Shanghai in 201x. One train stopped, the following train hit it.

tjohns8y ago

That shouldn't happen under normal circumstances. That's whole idea behind railway signals.

Rail segments (blocks) are supposed to be automatically locked off while a train is on that segment of track. No two trains can be on the same block at the same time. If a train stops, the signal guarding that block will remain red, ordering the next train to stop before it gets anywhere close.

taneq8y ago

If stopping doesn't fix things, you're not using enough of it. Time for networked emergency brakes on all trains!

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7dare8y ago

In fact, the crash at the origin of this whol debacle was caused by a train being stopped on the tracks and being rear-ended by another.

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Retric8y ago

Even then you should have some give aka Speed of X+3 MPH break, speed of x+1 MPH warning. You want fault tolerance not simply a hard limit without feedback.

abakker8y ago

Just a PID speed controller, maybe. Then, some boundary condition where when the controllers inputs mismatched from predicted outputs, then throw an error. But, if you're trying to drive 45, and you achieve 46 with a tail wind it doesn't seem necessary or safer to stop the train.

Zak8y ago

I think the idea is that if the operator is incapacitated or the control system is malfunctioning, stopping the train is the safest solution. While true, a multi-shot timer would be equally effective in detecting such a situation.

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0 comments

8 comments · 2 top-level

gsnedders8y ago· 6 in thread

The general principle in railway movement authority is that there's an easy fail safe: stop moving. If nothing moves, there can be no collision.

If something goes wrong? Stop the train. You can then figure out what went wrong and address it with no risk. Things shouldn't be going wrong, speeds shouldn't be being exceeded, etc.

ovi2568y ago

>If nothing moves, there can be no collision.

tjohns8y ago

That shouldn't happen under normal circumstances. That's whole idea behind railway signals.

taneq8y ago

If stopping doesn't fix things, you're not using enough of it. Time for networked emergency brakes on all trains!

1 more reply

7dare8y ago

In fact, the crash at the origin of this whol debacle was caused by a train being stopped on the tracks and being rear-ended by another.

1 more reply

Retric8y ago

Even then you should have some give aka Speed of X+3 MPH break, speed of x+1 MPH warning. You want fault tolerance not simply a hard limit without feedback.

abakker8y ago

Zak8y ago

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