No I think the system being proposed is different for one key reason. At the moment we have a system of absolute reservation and use, such that the track is "owned" by one train or another. This results in the priority line train stopping on track if there is a waiting train in the siding.
while it clears the area that the priority train wants, be that by signal or presignal.
The proposed system wants a signal that permits a train to reserve an area of track in advance of itself to prevent another train taking it, but in the event of finding that track already reserved, doesn't stop at the signal.
Moving left to right
standard signal=s
Pre-signal=p
junction = /
(Priority train)---p------s---------s---------------
(Siding train)------------s/
In this system if the siding train gets to the junction before the Priority train reaches the presignal it will result priority train stopping at the presignal since the area of the junction is reserved by the siding train
alternative proposed signal = Y
(Priority train)---Y------s---------s---------------
(Siding train)------------s/
In his system if the siding train arrives before the Priority train the Siding train will reserve the junction track as before, but this time the Priority train will having attempted to reserve the track, as before in the presignal case, not stop but reserve the track up to the signal before the junction. During the time that the siding train is traveling across the junction and past the last signal (i.e out of the way), the priority train will move on towards the signal before the junction, reserving the junction section as soon as it becomes free.
This will result in the trains on the priority line never stopping to wait for the siding train, provided the length of the section between Y and S is long enough for the siding train to clear the junction region before the priority train gets to the pre junction signal on the priority line.
This is what I understand to be the request. Think of a T road junction where a minor road meets a major road, the car joining waits for a large enough gap so as to not interupt the flow of traffic.
If anyone does have away of doing this with existing signals I apologise, and would the please explain how to do it to me :-D