Indian Practices

[khalid]

I deduce that the yellow aspect in India is primarily part of "speed signalling" for going into and out of loops or other turnouts etc rather than relevant to braking distance between signal posts in the "route signalling" that the UK uses. Hence it appears that my basic assumption that India would, because of its historic ties, have followed the UK rather than the European precedent is incorrect; I now guess that it may have been more based on USA or perhaps Australian practice.

The yellow aspect(on the Indian Railways)is not only used for entering or exiting loops but also to indicate to the driver that he is approaching a red signal if the route is set for the straight.
If the train is taking a diverging route then the signal will display only a yellow aspect in conjunction with an appropriate route indicator.This will be the case even if the loop starter has been taken off.The compulsory yellow aspect is maintained for the diverging routes because generally the turnouts on the Indian Railways are fit for slow speed movements of 10/15/30/40 KMPH.Same is the case for loop starters.They will also display a maximum of a single yellow irrespective of the aspect of the signal ahead.

The other thing that is very clear is that the locking, although with colour light signals, is actually very much that which I'd associate with "mechanical signalling" and the aspect controls seem to extend for two signal sections (i.e. in UK terminology the overlap of the signal section is in fact the entire route of the next signal section rather than to a specific defined track joint along that route). This has implications as the "exit" of the first route seems to be defined to be the line on which the 2nd signal in advance is depicted, rather than that of the exit of the route as I'd see it. I suppose the approximate equivalent in some ways of the UK Warner route is the ability at some loop signals to set a route to an exit signal with the points are set to divert any SPAD to a specifically provided overrun line and hence give the running line trapping protection.

While such an arrangement may sometimes be found on old mechanical signalling installations,the usual arrangement is to provide a minimum overlap of 120 metres beyond the next signal.(This overlap measures upto 180 metres for the block overlap on absolute block territory).All this is as per the General Rules of the Indian Railways.
The General Rules of the IR are available at this link:
http://www.zrtinr.in/gsr.aspx
In any case wherever colour light signalling has been implemented,the full complement of track circuits on the mainline are also provided complete with the overlap and all that.The overlap generally releases two minutes after the berthing track is occupied.The track sections beyond the overlap upto the next signal are always free for movement.

Also,all loop lines are protected by a sand-hump in the direction of movement so that in case of an overrun,the mainline will not be fouled.However uni-directional loops may not always have sand-humps in the trailing direction,instead a trap point will be provided.Hence warner routes need not be called for entry into the loop.(Actually there is no concept of a warner route on the IR.)

The back-lock tracks seem to be what the UK would have as sectional route locking release track circuits from the protecting signal to the last set of points in the route. This is just like mechanical practice whereby the only locking on the points is from the signal and therefore the signaller must not restore the signal lever until the last set of points have been traversed....... NR's practice for the mainline in the UK is that the signal can be normalised almost immediately the train has passed it, but the locking is maintained on each of the points by the sectional route locking until the train has passed ver that individual point; i.e. the route becomes progressively re-available as the train proceeds rather than being released all simultaneously. Hence this affects many things re module 3 and also the need for specific track joints when doing module 2.

Again this may be true for some of the mechanical signalling installations,but sectional route release is provided wherever panel interlocking or RRI is provided and back-locking on the signal is released as soon as the first set of points has been cleared by the train.

Similarly the time value in the Approach Track column would need explanation but this is to me indicating "when operated" with a time out rather than the "comprehensive release" applicable to certain signals for circumstances in which there is no train that can have seen them. I think that the need for the signaller to operate a device which increments a record count in addition to the time delay would need to be stated as an assumption as this is not a requirement in the UK;

Comprehensive approach locking is provided wherever suitable track circuits are available in the rear of the concerned signal.Where not available dead approach locking is provided by default.Whenever the signal is manually restored to red,a counter increments by one step(irrespective of approach locking conditions)and this must be recorded in the appropriate register with the reason for doing so.

The Remarks column certainly needs quite a bit of explanation when being viewed by UK eyes. CHR would not have been regarded as meaning a Crank Handle Release and I still don't understand why there are so many nor how they would be numbered.

Each set of points has its own crank handle release key which is generally kept locked in a location box in the field.Each key needs to be of a different ward(hence the large number of keys)to prevent its being used to operate some other set of points in the yard.The key is locked by a relay called a Key Locking relay and its slot is normally kept withdrawn to the cabin/panel.The point operation circuitry also ensures that the points can be driven only if the key is proved to be inserted and locked in the relay.

When the points need to be hand-cranked for any reason,the slot to the key locking relay(KLCR)is released from the cabin.The key is withdrawn and then inserted into the point machine which causes it to be disconnected from the cabin operating/detecting circuit.Now the cranking handle is inserted into the machine to bring to points to the required position.
Generally the Crank Handle Keys would be numbered according to the point numbers.

I am guessing the remarks such as 4RG/HG 1UG means that signal1 has a route indicator when routed up to signal 4 and derives its aspects from that signal which is itself capable of showing either Red or Green, but quite how this tells me what colour aspect signal 1 would itself display escapes me.

I've already explained the aspect sequence of signals for entry into loop lines as also while taking any diverging route.

Khalid,
India.