Astubbs Wrote:The spec specifies standage in both directions on the DVB. I interpret it in this case as meaning the freight will be held to allow fast passenger trains to proceed on the mainline in both directions, and also allowing trains joining the branch from the up main to overtake. Once the coast is clear the freight can proceed. Standage isnt only made available for trains shunting.
I believe you need main signals at both ends of the down valley branch as it mearly forms part of the freights main class route (B-C).
i doubt you would ever allow a train to proceed from an IPL some 700m over a viaduct!
hope im on the right lines, if not i may just have a long lyin on saturday
No get up and go to do the exam!
You certainly seem to have grasped the issue.
The plan shows arrows in BOTH directions on both the Up and Down Valley Branch; that means RUNNING moves in each directions. The fact that a line might have an arrow only in one direction does not rule out a shunt route in the contrary one.
As you say the spec is clear re requiring standage in both directions on the DVB. This could be used for holding a freight train that has come from UM to be clear of the Mains when a train is due to come across the viaduct and terminate in the Branch platform for example. Indeed it DOESN'T require standage on the UVB, so perhaps the best thing is to do is put a main aspect with PL at 1750 rather than the separate GPL that my earlier post suggested. The plus is that it is simpler and you might be able to get O/L that doesn't conflict the the junction. [Note that although UVB is to be used in the Down direction it can't be for through freight as it has nowhere to run to- amy train must be for Branch platform or Up siding.] The minus is that the signal wouldn't be opposite that on the DVB that has been positioned for maximum standage and there could be parallax problems for curved approach leading to signals apparently swopping position as driver approaches- so if you are tempted to do this then put a proviso note re your assumption!
You are right that we don't want a driver to run too far on a PL aspect- it is unreasonable to get driver to run a long distance "as far as the line is clear" and it takes a long time. 200m fine, 400m if necessary, 600m if there is no reasonable alternative. However I didn't think anyone was suggesting crossing viaduct on a shunt aspect, though one of the earlier posts was perhaps a little unclear.
PJW