Answer to 2005 Part A Q1

[PJW]

But still have confusion about 128A(S): I did not understand your statement well. If 107A(M)'s swinging overlap locks 210A N and 215B N, then as soon as it clear its overlap-EM, 215B can be set to R for 128A(S), but now, the train routed from 107 does not head on 128A(S). Why do you still consider 107A(M) in 128A(S) route locking?

The swinging overlap will NOT lock the facing points 210, but it would definitely lock (as trailing points in the overlap) 215N when 210N. I however was proposing that it might also be made to lock 215N (as pseudo point-to-point with 210) when 210R.
If however this is not implemented, there does need to be some locking that prevents one train being routed over 210R at the same time as another train is routed over 215R.
Think of it like this:
suppose the only points which 127B requires are 210R, 211R
suppose the only points which 128A requires are 215R, 211N, 212N
in this case (since 211 must be in one position or the other) than the two routes cannot both be set simultaneously. However a train using 128A would release 211 behind it once clears CN; would not want 127B to be able to set yet as CP would be foul of 210R, but 210 could have been reverse already in the scenario outlined above, so without effective locking provided by points some additional locking has to be provided. Note that whereas route locking is GENERALLY opposing locking it is not always; I hink it is this (and the headings sometimes used on the Control Tables) which may be causing confusion. Route locking can be in the SAME direction; e.g. for GK/RRT0044 locking, pre-set shunts etc

And another question: how do you jusitfy the length of TC, such as BE, BF. I can only find their total length is 450m, but can not know its own length, having difficulty in calculating the approach control time .

I agree there is not any certain clue but just make an estimate by proportion; AR looks to be a bit under 25% of the 450m so something around 100m.
Think why the IRJ would have been placed where it has been. a) 153 doesn't have a red so no definite need for a joint close to it, but sensible to have beyond the signal and relatively soon after it if practicable.
b) 144 has a PL of which viewing distance is 100m so looking at route box, notice that gives release as just AR occ. Hence we could assume that AR is no longer than 100m and could be comfortable that there would be no timer- this is simpler, saves money. Alternatively if feel that AR looks longer than 100m (and acknowledge that there is some advantage of the approach release not being very obviously associated with a track joint to avoid conditioning the driver to expect clearance), then could assume that it is say 125m and then show approach release time of say 5 seconds.
However, unless clearly in contradiction of signalling principles, I suggest just following the route box info; otherwise EXPLAIN why you are modifying. Don't worry about this small element too much; it really isn't going to make the difference between pass / fail of the exam- there are more important things to worry about