Hacker News Board Hacker News, browsed like a classic message board
Live data from Hacker News

SimSig: Railway Signalling Simulations

simsig.co.uk

Post reply on HN
Print view View original

61–70 of 101 posts

Re: SimSig: Railway Signalling Simulations

#61

Post by TylerE »

gsck wrote: post #10
fragmede wrote: post #6

Earlier quoted context omitted.

For people that want a railway simulator that includes game mechanics to drive a lot of complexity, try Factorio.

Pretty sure the developers of Factorio made a train game based around the train system in Factorio. Can't for the life of me remember its name but it looks rather good

He was one of the graphics contractors not a dev.

It is not very good. The game design is just and, failing to be either a good train sim or an interesting strategy game.

It basically flopped in early access.

Re: SimSig: Railway Signalling Simulations

#62

Post by TylerE »

londons_explore wrote: post #12

Railway signalling IMO is an area where a little research could dramatically increase the throughput of the railway network with a rather low cost. Todays railways mostly use fixed block signalling. Expensive and unreliable equipment ensures that there is only one train on each 'block' of railway track at the same time. That forces trains to be at least 1 or 2 blocks apart, which are frequently multiple miles long. E…

That isn’t how trains work. They take miles to stop.

Being able to stop any train on the network without risking it running in to another is not negotiable.

Re: SimSig: Railway Signalling Simulations

#63

Post by TylerE »

londons_explore wrote: post #16
dividuum wrote: post #13

Earlier quoted context omitted.

> A more advanced system would aim to have trains as close together as cars are on a freeway. https://en.wikipedia.org/wiki/European_Train_Control_System#...

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…

That’s a metric crapton of ifs. I would never get on such a system, it is fundamentally unsafe.

Re: SimSig: Railway Signalling Simulations

#64

Post by TylerE »

danhor wrote: post #53
jcranmer wrote: post #39

Earlier quoted context omitted.

There are two things that control the ruling headway on a subway system. The first is platform dwell time. While a train is stopped at a station, you cannot let another train move into its position as if it was going to start moving on schedule, because it's actually quite likely that it won't . Given that platform dwell time is about 30s, and taking into account time needed to decelerate and accelerate to/from a sto…

> and heavily reverse-branched systems like the DC Metro or NYC Subway struggle to make even 20TPH. I find this really interesting that is seems to be the limit for "big-boy" complicated subway systems, while there are many very complicated smaller systems that achieve much more. For example, a lot of the german Stadtbahn systems run somewhat long trains (up to 80m), run using conventional signalling systems undergro…

Trams often have rubber tires, which gravely increases acceleration and braking.

Also, 80m isn’t that long. Trains on the the DC metro are pushing 200. 8 cars long.

Re: SimSig: Railway Signalling Simulations

#65

Post by TylerE »

londons_explore wrote: post #18
p_l wrote: post #15

Earlier quoted context omitted.

Moving block systems are not really new, they just aren't distributed widely.

Moving block doesn't allow trains to get closer together than the braking distance. This would.

Saying trains should be closer than braking distance is like saying with devs shouldn’t support https. It’s something no expert in the field wound agree with.

Re: SimSig: Railway Signalling Simulations

#66

Post by danhor »

TylerE wrote: post #64
danhor wrote: post #53

Earlier quoted context omitted.

> and heavily reverse-branched systems like the DC Metro or NYC Subway struggle to make even 20TPH. I find this really interesting that is seems to be the limit for "big-boy" complicated subway systems, while there are many very complicated smaller systems that achieve much more. For example, a lot of the german Stadtbahn systems run somewhat long trains (up to 80m), run using conventional signalling systems undergro…

Trams often have rubber tires, which gravely increases acceleration and braking. Also, 80m isn’t that long. Trains on the the DC metro are pushing 200. 8 cars long.

> Trams often have rubber tires

No, they don't. There are a handful of weird french systems (and even less outside of France), but there are more ruber-tire metros than trams, I'm sure. They are rare and have been getting rarer.

80m is in the lower half for metros, but long in the context of systems having on-street portions (exceeding the german legal limit of 75m with a special exception). It's also on the long end for small metro systems.

Re: SimSig: Railway Signalling Simulations

#67

Post by andruby »

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.

That's interesting, in Belgium I think it's "2 seconds", or at least that's what was promoted recently on the radio.

You should be able to sing "Last night a DJ saved my live", which is a bit more than 2 seconds. I liked that, because it's one you can actually test for while driving.

I find it a lot harder to estimate 50m while driving at 100km/h

Re: SimSig: Railway Signalling Simulations

#68

Post by [deleted] »

whartung wrote: post #49
lqet wrote: post #42

Earlier quoted context omitted.

> 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.

[deleted]

Re: SimSig: Railway Signalling Simulations

#69

Post by Animats »

My favorite simulator for railway signals is NXSYS.[1] This simulates General Railway Signal's NX system down to the relay level. NX had the first "intelligent user interface" device. When a train enters the interlocking, the dispatcher pushes an entry button to indicate they want to dispatch that train. All the possible exit points then light up. The dispatcher then pushes the button at the appropriate exit light, and all the signals and switches are set up for that route.

Routing within the interlocking is automatic. Exit lights only light up if there's an available path. The system is aware of trains in the interlocking, switches locked for maintenance, and the actual position of switches, signals, and train stop devices. As a train moves through the interlocking, track space and switches are released behind it automatically, becoming available for other trains.

Today this seems routine, but it was a huge breakthrough in the 1930s. The original marketing brochure is available online.[2]

[1] https://bernardgreenberg.com/Subway/

[2] https://anyflip.com/lbes/vczg

Re: SimSig: Railway Signalling Simulations

#70

Post by NovemberWhiskey »

bluGill wrote: post #51
londons_explore wrote: post #35

Earlier quoted context omitted.

The market for people transport is huge. Imagine the cost of all apartments in manhattan @ $3000/sq foot. Now imagine the cost of the same apartments built in upstate new york @ $250/sq foot. A transit provider who can get people from a house in a rural area to manhattan in 15 mins can pocket that difference, which is huuuuge .

> Imagine the cost of all apartments in manhattan @ $3000/sq foot. Does such a thing exist? A tiny bathroom is 25sq feet - or $75000. That just seems too much. Zillow lists studio apartments in Manhattan for $3000-$5000/month. They also list apartments in New Jersey for $250/month just 30 miles away (1 hour drive to Manhattan according to maps). At that distance we don't need fancy hyperloop, we just need good higher…

$2,000 to $3,000 per square foot is absolutely the asking price for condos in parts of New York like Tribeca and Soho.
Post reply on HN