2010 CTs, points 137 & 148

[Peter]

[The overlap for 484 goes beyond the crossing between 148A and 148B, so by the same logic that you have included the routes from 484, you also need to include the route from 494 up to 484 which requires the overlap.]

When an overlap extends through a set of points like 148 do you have to include these extra tracks as part of the route release for 494 signal i.e. EL track circuit?

So ignoring the swinging overlap
Route-----Tc's clear-------------Occ---t
494A(M) - EK, EL, (EG, EH, EJ..... EJ....20s)

Any secondly if we encounter a swinging O/L do we have to condition this into the release (something like)
Route-----Tc's clear-------------------------------------Occ---t
494A(M) - EK, {(EL or 146R),(CJ or 146N)}, (EG, EH, EJ..... EJ....20s)

Doesn't look right (as it probably isn't) but there doesn't seem to be any real benefit in including TC's (EL or CJ) passed the dead locking tracks. Could we not just release all point locking associated with 494 once EL becomes clear after having been occupied (which would presumably only happen after a SPAD?)

Think I've lost the plot on this a bit.

Cheers

I think you are talking about two different things. When you are considering the route locking release when a route is an opposing route for another route, you will take the release conditions up to the end of the end of the relevant route. When you are considering at what point a set of points ceases to be route locked by a route set over it, you would need to go as far as the position where the route affects the points.

In your example, if there was a ROUTE which opposed 494A(M), the outline of the release that you give above would be correct, ie we need to know that the train that has taken 494A(M) has either taken the whole route, including the overlap (up to EL) or that it has come to a stand at the signal so the overlap route locking is not required. I say outline as, given the braking distances quoted and the train lengths, the train standing on EG (and probably EH) when 484 is at red is quite unlikely.

As far as the 146 POINTS would be concerned, yes, 494A(M) set would apply route locking to them. Like you said, ignoring the swinging OL and taking the OL to EL track, if the train takes the route and SPADs 484, the route locking would include EK but there is no point maintaining it once EK is clear (ie if the back of the train has got as far as EL).

I recall a conversation with PJW about the subtlety of including the deadlocking track in the route locking or not and I think the comment was that in certain route relay interlockings is was pointless because there was no way to test whether it was there or not. In UK SSI practice, it is normal to include it.

I hope that is clear and that I have conveyed my understanding. I also hope my understanding matches some sort of reality!

Peter