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| Wirrall Loop Signalling 17/05/2019 at 00:51 #118339 | |
DaveHarries
1285 posts |
Greetings, One thing I noticed when playing on the Wirrall Loop was that signals prior to reds were showing Green, not Yellow as I would expect, as shown for P3 at James Street. I know the repeater is correct: it is signals 521 and 531 I am referring to. Not knowing the area is that correct IRL or is this a bug? Dave 
Post has attachments. Log in to view them. Last edited: 17/05/2019 at 00:52 by DaveHarries Reason: None given Log in to reply |
| Wirrall Loop Signalling 17/05/2019 at 04:05 #118340 | |
headshot119
4869 posts |
There's a section of the manual which covers this. Quote: Loop Line Signalling "Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Log in to reply |
| Wirrall Loop Signalling 17/05/2019 at 08:52 #118341 | |
kbarber
1743 posts |
headshot119 in post 118340 said:There's a section of the manual which covers this.This, as I understand it, is pretty much standard 'metro' style signalling. Signals are normally associated with train stops (another thing to go wrong...) and overlaps are calculated rather than a standard length, so any train tripped from line speed will be stopped within the overlap. Drivers are expected to stop on sight of a red (sighting distance is always at least braking distance); repeaters are only provided if curvature or obstacles limit sighting distance, or on platforms to aid dispatch. It's the same system London Underground use (although it's being superseded as TBTC spreads, currently appearing on the 'surface lines' network). Log in to reply |
| Wirrall Loop Signalling 17/05/2019 at 09:14 #118342 | |
Splodge
720 posts |
A similar system applied on Metrolink in Manchester where block signalling was installed (mostly removed now and replaced with standard tramway signalling). Repeaters were only provided in areas of poor visibility, and most red/green signals were at a station which was provided with a 'station ahead' board (which was in effect a fixed distant although of a different style to heavy rail), though there were plenty of areas with good sighting where you could go from red/green to red/green.
There's the right way, the wrong way and the railway. Log in to reply |
| Wirrall Loop Signalling 17/05/2019 at 12:30 #118349 | |
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clive
2789 posts |
The Tyne & Wear Metro also runs mostly on 2-aspect signals. Repeaters are only used where the sighting distance is less than the braking distance. One oddity about their system is that the last signal before a station shows yellow rather than green for off, on the basis that you're going to be stopping anyway. Where stations are close together, there's a "station ahead" sign under the previous starting signal - this sign is a standard road "traffic lights ahead" sign. Log in to reply |
| Wirrall Loop Signalling 18/05/2019 at 09:09 #118356 | |
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kbarber
1743 posts |
clive in post 118349 said:The Tyne & Wear Metro also runs mostly on 2-aspect signals. Repeaters are only used where the sighting distance is less than the braking distance.I wonder if that might also be about overlaps? I understand LT practice has a near-zero overlap on the platform starter because, regardless of the line limit, all trains are considered to be starting away from rest. This is why any underground train passing through a station non-stop has to reduce speed to walking pace. (Where that is a regular occurrence, such as stations that close at weekends, it is often further enforced by holding the platform starter at red until a train is closely approaching it.) Regardless of such provision, a yellow rather than a green on the approach makes a lot of sense as a reminder that the platform starter must be approached slowly, even if you're working ecs and passing non-stop. Log in to reply |
| Wirrall Loop Signalling 18/05/2019 at 10:34 #118357 | |
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headshot119
4869 posts |
kbarber in post 118341 said:You're quite right Keith, the exact limits of the tripcocks are noted in the reference section of the manual, but all of the underground signals have them. Although it is an extra thing to go wrong, at least they fail right side unlike TPWS. "Passengers for New Lane, should be seated in the rear coach of the train " - Opinions are my own and not those of my employer Last edited: 18/05/2019 at 10:34 by headshot119 Reason: None given Log in to reply |
| Wirrall Loop Signalling 19/05/2019 at 08:51 #118372 | |
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metcontrol
227 posts |
kbarber in post 118356 said:I wonder if that might also be about overlaps? I understand LT practice has a near-zero overlap on the platform starter because, regardless of the line limit, all trains are considered to be starting away from rest. This is why any underground train passing through a station non-stop has to reduce speed to walking pace. (Where that is a regular occurrence, such as stations that close at weekends, it is often further enforced by holding the platform starter at red until a train is closely approaching it.) Regardless of such provision, a yellow rather than a green on the approach makes a lot of sense as a reminder that the platform starter must be approached slowly, even if you're working ecs and passing non-stop.Much as most conventionally signalled LU stations have a green aspect on the last home signal before a platform, there is a further repeater for the station starter. Platform repeaters were provided mainly for when trains had guards (allowing the guard an indication of the starter to avoid giving the right to a train stood at a red signal). However they are still maintained and still provide an indication of the starter as a train arrives in a platform - even if the train is going to stop anyway and even if the starter has a time delay before clearing. Generally platform repeaters will be found mounted at more or less train height somewhere towards the back half of the platform - though of course there are numerous exceptions dependant on platform geography and other external factors. Log in to reply The following user said thank you: kbarber |