Upcoming Games


Full list
Add a game

Wirrall Loop Signalling

You are here: Home > Forum > Simulations > Released > Sandhills (Merseyrail) > Wirrall Loop Signalling

Page 1 of 1

Wirrall Loop Signalling 17/05/2019 at 00:51 #118339
DaveHarries
Avatar
914 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 00:51 by DaveHarries
Reason: None given

Log in to reply
Wirrall Loop Signalling 17/05/2019 at 04:04 #118340
headshot119
Avatar
3196 posts
Online
There's a section of the manual which covers this.

Quote:
Loop Line Signalling
All Stop signals between Green Lane / Birkenhead Park and around the Liverpool Loop Line are two aspect (Red/Green). As repeaters are not provided for all signals, it is possible for a Green-> Red aspect sequence to be displayed to drivers. Unusually, however, there are no restrictions on operating these signals- they may be cleared at any time, and drivers will accept a Green-> Red aspect sequence without a Yellow aspect, or delayed clearance of the preceding signal. This reflects real life practice.

"CHECK Do you stop at Capenhurst?" - 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
Avatar
1400 posts
headshot119 in post 118340 said:
There's a section of the manual which covers this.

Quote:
Loop Line Signalling
All Stop signals between Green Lane / Birkenhead Park and around the Liverpool Loop Line are two aspect (Red/Green). As repeaters are not provided for all signals, it is possible for a Green-> Red aspect sequence to be displayed to drivers. Unusually, however, there are no restrictions on operating these signals- they may be cleared at any time, and drivers will accept a Green-> Red aspect sequence without a Yellow aspect, or delayed clearance of the preceding signal. This reflects real life practice.
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 09:13 #118342
Splodge
Avatar
397 posts
Online
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 12:29 #118349
clive
Avatar
1904 posts
Online
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 09:08 #118356
kbarber
Avatar
1400 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.

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.
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 10:33 #118357
headshot119
Avatar
3196 posts
Online
kbarber in post 118341 said:


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).
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.

"CHECK Do you stop at Capenhurst?" - Opinions are my own and not those of my employer
Last edited: 18/05/2019 at 10:33 by headshot119
Reason: None given

Log in to reply
Wirrall Loop Signalling 19/05/2019 at 08:50 #118372
metcontrol
Avatar
184 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