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SimSig: Railway Signalling Simulations

simsig.co.uk

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Re: SimSig: Railway Signalling Simulations

#41

Post by sneak »

thanzex wrote: post #33
londons_explore wrote: post #16

Earlier quoted context omitted.

This still doesn't allow train spacing of less than the braking distance. Braking distance of trains is large (due to high uncertainty in track friction), which still means trains are typically 1 minute or more apart when moving fast. As long as you have comms with the trains around, it's clearly possible to safely go less than the braking distance, as long as you can be sure of the behaviour of the train ahead, even…

I think that's not something that can be avoided, unfortunately. Any number of things could cause a train to suddenly stop. A mechanical failure, derailment, collision, a wagon could get detached... On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between…

> On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between vehicles.

No. Unsafe drivers have illegally decided this, but in most jurisdictions it is your responsibility to stop your vehicle short of the one in front of you. You should be maintaining stopping distance from your vehicle to the one in front.

Re: SimSig: Railway Signalling Simulations

#42

Post by lqet »

sneak wrote: post #41
thanzex wrote: post #33

Earlier quoted context omitted.

I think that's not something that can be avoided, unfortunately. Any number of things could cause a train to suddenly stop. A mechanical failure, derailment, collision, a wagon could get detached... On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between…

> On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between vehicles. No. Unsafe drivers have illegally decided this, but in most jurisdictions it is your responsibility to stop your vehicle short of the one in front of you. You should be maintaining stoppi…

> You should be maintaining stopping distance from your vehicle to the one in front.

I am not so sure. In Germany, for example, the minimum required distance to the car in front of you is "speed in km/h divided by 2 in meters". So for 100 km/h, you are required to keep a minimum distance of 50 meters. I very much doubt that you can stop a car going 100 km/h within 50 meters.

Re: SimSig: Railway Signalling Simulations

#43

Post by [deleted] »

londons_explore wrote: post #25
pixiemagic wrote: post #20

Earlier quoted context omitted.

What happens if there's some other reason to brake, such as an unreported fallen tree on the line ahead?

You can still brake - you just need (automatic) agreement of all trains behind you to do so. You aren't allowed to brake 'as much as possible' anymore - instead the best you can achieve is 'the best the worst of the trains behind me can achieve'.

[deleted]

Re: SimSig: Railway Signalling Simulations

#44

Post by lqet »

londons_explore wrote: post #40
garaetjjte wrote: post #38

Earlier quoted context omitted.

If one train derails for some reason, then every single train on the line crashes in the greatest pileup ever. Great.

Thats already the case for carriages within a train.... And people are fine with it. We're also fine with the risk of a derailment onto a neighbouring track with traffic going the opposite direction. We could have tech which detects that, but we do not.

> And people are fine with it

The thing you are missing is compartmentalization. A modern high-speed train can hold around 1,000 people. This is the maximum number of people that could die in an accident (ignoring trains on other tracks or people next to the tracks). What you are proposing is essentially a train of infinite length, with virtual (software) coupling between groups of carriages. But then there is no limit to the maximum number of deaths in an accident. If you have 50 high-speed trains all traveling in this virtually coupled manner, a single accident may cause 50,000 casualties. People would not accept this, and no sane policy maker would allow it.

Note that if you consider derailments into neighboring tracks, you still have an upper limit of 2 times maximum train capacity, in our example 2,000.

Re: SimSig: Railway Signalling Simulations

#45

Post by shagie »

cmul wrote: post #27

For German speakers: https://www.estw-simulator.de/index.html https://www.estwsim.de/cms/index.php These have been around for a while and quite closely mimic (slightly older) German signalling specifications for signaller interfaces. My company builds such systems as test and demonstration systems for real railway projects with respective functional safety constraints. If you're interested to learn more about the sig…

Also in the German train signaling ... https://www.eisenbahnbetriebsfeld.de

A Tom Scott video on it - The world's most useful model railway https://youtu.be/6TLcaJdsRr0

Re: SimSig: Railway Signalling Simulations

#47

Post by thanzex »

sneak wrote: post #41
thanzex wrote: post #33

Earlier quoted context omitted.

I think that's not something that can be avoided, unfortunately. Any number of things could cause a train to suddenly stop. A mechanical failure, derailment, collision, a wagon could get detached... On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between…

> On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between vehicles. No. Unsafe drivers have illegally decided this, but in most jurisdictions it is your responsibility to stop your vehicle short of the one in front of you. You should be maintaining stoppi…

Not really. In my country, at least, it is explicitly stated in driving theory manuals to maintain at least one reaction distance between the car in front of you.

For a car traveling at 100Km/h the stopping+reaction distance would mean more than 130m, which is a quite large and possibly impractical for higher traffic scenarios.

Re: SimSig: Railway Signalling Simulations

#48

Post by danhor »

londons_explore wrote: post #25
pixiemagic wrote: post #20

Earlier quoted context omitted.

What happens if there's some other reason to brake, such as an unreported fallen tree on the line ahead?

You can still brake - you just need (automatic) agreement of all trains behind you to do so. You aren't allowed to brake 'as much as possible' anymore - instead the best you can achieve is 'the best the worst of the trains behind me can achieve'.

You could also characterize the maximum braking ability of the train in front of you and the minimum braking ability of your own train and determine the needed distance for any given speed based on that. This would of course be more complicated and probably be solved by only including broad categories of trains (i.e. only two sets of values for either passenger trains or freight trains).

Re: SimSig: Railway Signalling Simulations

#49

Post by whartung »

lqet wrote: post #42
sneak wrote: post #41

Earlier quoted context omitted.

> On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between vehicles. No. Unsafe drivers have illegally decided this, but in most jurisdictions it is your responsibility to stop your vehicle short of the one in front of you. You should be maintaining stoppi…

> You should be maintaining stopping distance from your vehicle to the one in front. I am not so sure. In Germany, for example, the minimum required distance to the car in front of you is "speed in km/h divided by 2 in meters". So for 100 km/h, you are required to keep a minimum distance of 50 meters. I very much doubt that you can stop a car going 100 km/h within 50 meters.

You do t need to stop a 100 km/hr car in 50 meters because, barring that sudden brick wall appearing ahead of the car in front of you, they’re not stopping in 50m either.

The 50m is the reaction buffer, not the stopping buffer.

It’s also prudent to give more leeway to vehicles you can not see around to avoid the large truck swerving to avoid the refrigerator that just fell out of the truck in front of them problem.

Re: SimSig: Railway Signalling Simulations

#50

Post by corobo »

lqet wrote: post #42
sneak wrote: post #41

Earlier quoted context omitted.

> On roads we have millions of vehicles, carrying on average a very small amount of people, around 1.5. For efficiency sake we have accepted the risk of staying within reaction distance instead of stopping distance between vehicles. No. Unsafe drivers have illegally decided this, but in most jurisdictions it is your responsibility to stop your vehicle short of the one in front of you. You should be maintaining stoppi…

> You should be maintaining stopping distance from your vehicle to the one in front. I am not so sure. In Germany, for example, the minimum required distance to the car in front of you is "speed in km/h divided by 2 in meters". So for 100 km/h, you are required to keep a minimum distance of 50 meters. I very much doubt that you can stop a car going 100 km/h within 50 meters.

At least with cars they also have the option to swerve away from the chaos if the stopping distance is too short.

Not to disagree, just throwing in a variable that trains don't have

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