what is signal aspect diagram

[onestrangeday]

Hi signal professionals:

I am still new to the signallling industry.
I have few questions as follow

1. " what is signal aspect diagram" ?

2. is "signal aspect diagram" = "signal aspect sequence"

3. can anyone provide a copy of 'signal aspect diagram' or "signal aspect sequence", i have no idea what's looks like ?

4. how would you draw out the aspect sequence for all the signals a driver would see before reaching a red signal.



thanks


william

[PJW]

Hi signal professionals:

I am still new to the signallling industry.
I have few questions as follow

1. " what is signal aspect diagram" ?

2. is "signal aspect diagram" = "signal aspect sequence"

3. can anyone provide a copy of 'signal aspect diagram' or "signal aspect sequence", i have no idea what's looks like ?

4. how would you draw out the aspect sequence for all the signals a driver would see before reaching a red signal.
thanks
william

I consider they are one and the same; I generally call them Aspect Sequence Charts but sometimes Diagrams.

You will find an example of several attempts posted on this website; look at the attachments for the posts in this section.

Look at these diagrams and you'll see the horizontal lines that join the aspect of the signal ahead being joined to the one which reads up to it and thereafter to the signal whiich reads up to that one. In that manner the extent of the restrictive aspects displayed on the approach to a signal at red can be clearly be identified.

Although aspect sequence nowadys is primarily in Module 3, it is the Module 2 Study Pack which has the information (for historical reasons reflecting the fact that the exam used to be divided slightly differently)

[onestrangeday]

Hi signal professionals:

I am still new to the signallling industry.
I have few questions as follow

1. " what is signal aspect diagram" ?

2. is "signal aspect diagram" = "signal aspect sequence"

3. can anyone provide a copy of 'signal aspect diagram' or "signal aspect sequence", i have no idea what's looks like ?

4. how would you draw out the aspect sequence for all the signals a driver would see before reaching a red signal.
thanks
william

I consider they are one and the same; I generally call them Aspect Sequence Charts but sometimes Diagrams.

You will find an example of several attempts posted on this website; look at the attachments for the posts in this section.

Look at these diagrams and you'll see the horizontal lines that join the aspect of the signal ahead being joined to the one which reads up to it and thereafter to the signal whiich reads up to that one. In that manner the extent of the restrictive aspects displayed on the approach to a signal at red can be clearly be identified.

Although aspect sequence nowadys is primarily in Module 3, it is the Module 2 Study Pack which has the information (for historical reasons reflecting the fact that the exam used to be divided slightly differently)

Hi PJW:


thanks for your explanantion. I have looked the past post. but i still don't understand (i think i only have a general idea,but i would like to know more in detail), can you explain more in detail ? or do you know where i can get more information from ? (books ??)


thanks


william

[Peter]

Hi PJW:


thanks for your explanantion. I have looked the past post. but i still don't understand (i think i only have a general idea,but i would like to know more in detail), can you explain more in detail ? or do you know where i can get more information from ? (books ??)

thanks
william

The former Railway Group Standard has some information about what aspect sequences mean and, in its explanation of what should be shown, has some diagrams which support the words.

Peter

[onestrangeday]

Hi PJW:

thanks for your reply. I'll check on that, if i don't understand, i'll ask.


william

Hi PJW:


thanks for your explanantion. I have looked the past post. but i still don't understand (i think i only have a general idea,but i would like to know more in detail), can you explain more in detail ? or do you know where i can get more information from ? (books ??)

thanks
william

The former Railway Group Standard has some information about what aspect sequences mean and, in its explanation of what should be shown, has some diagrams which support the words.

Peter

[onestrangeday]

Hi Peter:

The signalling system i'm working is fully automatic and with only two signals, that is there are only 'green--proceed' and 'red--stop' signal aspect, what would be the signal aspect sequence like ?

or it doesn't need signal aspect sequence, since there are only go and no go signal ??

william

Hi PJW:

thanks for your reply. I'll check on that, if i don't understand, i'll ask.
william
quote='Peter' pid='2544' dateline='1296557170']

Hi PJW:
thanks for your explanantion. ...... where i can get more information from ? (books ??)
thanks
william

The former Railway Group Standard has some information about what aspect sequences mean ....
Peter

[/quote]

[PJW]

[quote='onestrangeday' pid='2564' dateline='1296916232']
Hi Peter:

The signalling system i'm working is fully automatic and with only two signals, that is there are only 'green--proceed' and 'red--stop' signal aspect, what would be the signal aspect sequence like ?

or it doesn't need signal aspect sequence, since there are only go and no go signal ??

william
[//quote]

First of all if the system is fully automatic then we need to ask why there are signals at all. It could either me
a) that there is still a driver in charge of every train who has the responsibility of stopping in the right places but can generally turn on some form of Automatic Train Operation and let it get on with driving. Perhaps the driver has to open / close the doors at station and / or be here to reassure passenger.
b) Perhaps the signals aren't actually used in normal operation at all, but are only povided in order to be able to keep some form of tran service operating safely in periods of failure of the ATO or significant external disruption for some reason.

In case a) I assume that trains must be able to "stop on sight" from their normal speed; i.e. if a driver sees the signal at red then the sighting distance is sufficiently long ompared to the braking distance that can bring train safely to a halt- very much like driving a car apart that the distances may well be greater (but of course depends on the type of train and the operational speed).

In case b) then signals may not have enough sighting distance for the usual speed of train operation but in the "degraded mode" there would have to be a low speed limit imposed when driving manually so that there was enough distance in which to stop from seeing the red signal.

Therefore in neither case would there be a need for a warning signal and so you are correct; no "aspect sequence" would be needed.
We'd call this a true "2 aspect signalling" system. Even without any form of automatic train operation, such systems are used for mnay tramways and some metros in the UK. Indeed although London Underground generally provides yellow / green "repeater signals", for most of the network these are really a supplement to increase the viewing range of the red / green rather than a "distant" (as it would be on Network Rail).

I do not know [someone who does please post!], but I doubt whether they have aspect sequence diagrams. Indeed the colour light isn't really of prime importance anyway (it isn't proved alight as it would be on Network Rail)- the important part of the "signal" is far more the trainstop since this will apply the brakes if the train passes the signal and will stop it within the locked overlap and therefore safely.

On some forms of automatic railways though I guess that there is a sort of aspect sequence, in that the permissible speed code for one section of track depends upon the speed code of the following section. Nowadays technology has generally moved on and trains have some form of direct communication with the control centre and have far more detailed knowledge of where they are and how much further they have authority to travel, compared to the more limited systems of yesteryear.
Again this is an area that I, as yet, have little knowledge so would welcome additional information from someone closer to the subject.

[adikarina]

Hi,
In LU we dont use Aspect sequence charts, but we do include the aspects in control tables (certain sites / lines only).

For the module 3 exam, I had to understand the Aspect Sequence Chart... basically it shows how the signal aspects are shown to the driver in direction of travel. It shows main (R/G) and repeater (Y/G) signals. Also Junction/Route indicators for the different routes.

For the exam you will need to familiarise with the Network Rail symbols and signals (3, 4 aspect signals with single and double flashing yellows).
I would recommend looking at a typical Module 3 layout for control table and going through the signals and understanding the routes. Use highlighters to colour the different routes if it makes it clearer.

There are also some model answer aspect sequence charts that are part of the IRSE Exam model answers pack (

[Peter]

I am trying to upload files, but am not able to. Will try and sort it out.
Aditi

What sort of file type are you trying to do and how big? I'll make sure the permissions are right as not all attachments are allowed by default.

Peter

[adikarina]

Hi Peter,
There are 5 files all PDF and less than 400KB.
Thanks
Regards
Aditi