[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.
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.
PJW