(08-09-2010, 09:09 PM)jenni.joseph9 Wrote: Hi,
Am trying to attempt 2009 paper and got struck at the Shunt Overlap. In the layout the overlap symbol is shown for few shunt routes and not shown for the other.
For example, route 418C(S) leading to 382 - overlap symbol is shown on the down branch line as 180. Does that symbol is applicable for this shunt route also or used purely for main moves like 416C(M).
Route from Independent ground PL(Shunt) to another Independent PL is provided with an overlap where as the route from GPL to main signal(i.e 418C(S) ) is not shown with the shunt overlap.
So, when the overlap can be considered for the shunt move and when can be omitted? Please clarify.
Sorry I missed this post initially.
The way I read this plan is that it is assuming that all shunt routes have overlaps.
Therefore where there is an overlap at the exit signal, then the shunt routes reading up to that signal will utilise this as their overlap (assuming non-permissive shunt route; where there is a possibility of being required to join a train on the berth track for example, then an overlap is not applicable).
The plan denotes shunt overlaps where the overlap shown is ONLY for shunt routes up to the exit signal, not for other classes. I think in this case that it is wherever there are no running moves provided on the layout; as you say where the exit signal is a PL then there are shunt overlaps shown (as of course no running moves up to the exit) but where there is a main signal then almost certainly (but not definitively) there will be a running move up to the exit and hence no shunt overlap shown as there will be an overlap marked anyway.
Note however that it would be possible to define a shunt overlap that is shorter than that for a running move (e.g. 75m rather than 180m) but I suspect that it would only in reality be worth doing if a convenient track joint needed to exist for other reasons, otherwise would add significantly to costs for little real benefit. However where there is a ROL provided for any Warning class route, then I'd expect the shunt route to use this rather than the full overlap.
Does that resolve for you?
This represents what is now NR practice, but only became like this within the last few years so little of the network currently embodies this practice
PJW