23-09-2009, 10:30 PM
(23-09-2009, 07:46 PM)priyman Wrote: ------------------------
PJW:
# overlaps just measured to be 180m beyond signal and placed without thought within S&C.
I thought i did place them with thought, but you just can't avoid swinging overlaps sometimes, or are you thinking about something else? I'm thinking at Station E signal 10 or 12 overlaps.
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Priyank
The overlap beyond sig 10 results in the AR/AQ joint being foul of 103R; therfore AQ must lock these points normal so delays the time when a route can be set from bay platform to branch after a train on the Up Main. If you had placed the joint opposite 103C then it would have been at clearance, resulting in earlier release of locking since AQ would not need to lock- the O/L would be better at 210m from signal 10.
If however the permissible speed had been lower then you may have been able to justify a shorter, reduced, overlap at the AS/AT joint.
Similarly joint BS/BT is foul; this means that if 103 are Reverse then the overlap beyond signal12 is not available and therefore a train would have to be held at 166 rather than being permitted to enter the station. In this case I'd have put the overlap at the BS/BR joint and additionally defined a "Restricted" overlap [ROL] as far beyond signal 12 as I could but just short of the unnumbered crossover to the Branch. This would need BT to be split into two separate tracks and 166 given a Warning class route.
The message is THINK about the significance of the overlap positions to interlocking (yes it is module 2 but apply what you know about Control tables from module 3)- don't just automatically measure the standard 180m and plonk down an overlap symbol.
PJW