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Post by drainrat on Aug 24, 2016 8:53:25 GMT
I know this thread is a few months old but I've just joined. There is no yellow light between Leyton and Stratford. There is an RGI repeater in that area (it's like a standard RGI but with three yellow aspects instead of red) but a driver would never normally see it lit. Been so long I looked but isn't the RGI on approach to the tunnel?
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Post by drainrat on Aug 24, 2016 8:52:01 GMT
The "yellow" aspect is just a dirty signal lens. You can overrun a signal (SPAD) in coded with the trains emergency brakes coming on as soon as you enter the next section. The ATP puts the brakes on if sitting at a red signal for a certain period (sorry cant remember the exact time - got 60 secs in my head by probably wrong) so the train wont then move until it receives a code to proceed. Theres a bit more to it but thats the basics. It all depends on the location, some places you can hear the ATP drop out almost immediately, other places it doesn't drop out at all no matter how long you're sat there. train can move at any time!
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Post by drainrat on Aug 23, 2016 13:38:43 GMT
Fair enough, that's very much what I'd imagined, but it's nice to have a chance to get it confirmed Thinking about it, it's possible that both routes are approach released given how little room for error there is at Bank, you want as much speed control as you can get away with don't you? It strikes me as likely that if the signaller called for the straight route at WK7 early it might very well not clear immediately anyway, but that's pure speculation on my part. As far as I can tell, WK7 is always approach-cleared, and will never clear until the train has passed WK700. However, I can't see any speed control on WK7, and it appears WK700 will clear without speed-control if either route from WK7 has been selected. So, if correct, with the route set all the way into either platform the driver will see: 1) WK700 showing green over yellow, with WK7 at red. 2) Once the train passes WK700, WK7 will clear straight away for either route. If no route is set into Bank, the driver will see: 1) WK700 showing red, which will clear to green over yellow subject to the timing conditions being satisfied. 2) WK7 will clear when the route is set. Does this sound right? Yes, that's right
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Post by drainrat on Aug 22, 2016 21:41:04 GMT
I imagine they can, and also the TO can check and and possibly change at panel at bank. Thinking about it, it's possible that both routes are approach released given how little room for error there is at Bank, you want as much speed control as you can get away with don't you? It strikes me as likely that if the signaller called for the straight route at WK7 early it might very well not clear immediately anyway, but that's pure speculation on my part. Depending on the route we can get 4 policemen into plat 8 or 3 into plat 7. So speed control is key, route locking would ensure it clears as soon as platform is empty and the approaching train is on the approach track. They often do it manually if the service starts to run late and they start using both platforms. Turnaround in peaks can be as little as 20 secs, also turning round in plat 8 adds 30 secs per reverser due to slow speed leaving the platform (15 kph), it creates blocking back into bank.
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Post by drainrat on Aug 22, 2016 21:22:01 GMT
Outside the peaks, it does indeed clear early to 7s as you get a straight green to plat 8 so train speed is high at 40kph over the points, into plat 7 (to run a faster peak service) speed needs to be checked for consecutive policemen set at 15 then 10 kph. If WK7 is cleared early, do you nevertheless get a yellow on WK7R, or does it simply show no aspect? Or do you get a green as you would expect, only the fine diagram on harsig's website seems to show no green aspect on WK7R? I've never experienced WK7 being cleared early before you round the curve, it's always red on approach so you only see yellow. Clearing early to us would be as we pass 700 rather than approaching WK7. I've never seen a green/green on WK7R/700, only a red or green/yellow, even when both platforms are empty. I imagine they can, and also the TO can check and and possibly change at panel at bank.
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Post by drainrat on Aug 22, 2016 21:11:11 GMT
Incidentally, other changes that pre-empted the 5 train service was: - Taking out 4rd
- TES on 5rd
- 2 SAs on arrivals
- Double step back at Waterloo depot
- Moving step back room further up 5rd, hence 4rd being decommissioned
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Post by drainrat on Aug 22, 2016 21:01:49 GMT
Green is no longer used approaching terminals on Network Rail in response to collisions years and years ago. Decades, I believe. LU uses 2-aspect signalling, it has greens into terminal platforms and has had since Moorgate. WK700 looks to me like a pretty standard speed control signal. So what happens is if WK7 is red, WK700 will be red. As a train approaches and it enters the relevant track circuit, a timer begins. After the time has elapsed, WK700 will clear. If the train is going too fast it will pass WK700 before the time has elapsed and before it has cleared. It will therefore be tripped to a halt and will (in theory at least) not collide with any train which might be proceeding over the crossover. The timer is such that the train will have to have slowed down quite a bit before WK700 can clear. As a result, when it is allowed to proceed, it will not be able to be going that fast when it reaches WK7. Should it then fail to stop at WK7, it will be tripped to a halt before reaching the crossover and perhaps colliding with a train. WK700 is a separate signal. With it, is WK7R - a repeater for WK7. A repeater. If WK7 is red, WK7R is yellow. If WK7 is green, ordinarily, a signal like WK7R would be green. However, by the looks of it, there is no green aspect provided on WK7R. Presumably, WK7 clears quite late, and so WK7 will never be showing green when a train passes WK700 and the repeater WK7R, so there's no need for a green aspect on WK7R. When WK700 is red, WK7R is suppressed, it doesn't show anything. When WK700 is green, WK7R goes yellow. So a driver will approach WK700 and see a red aspect. He will slow down. When the timer has elapsed, WK700 will go green and WK7R will illuminate its yellow aspect. The driver will see green over yellow. He will proceed towards WK7 which will presumably clear as he approaches or - if it is unable to clear - when it is able to do so. Having said that, I've just checked the Video125 driver's eye view video and it looks a lot like WK700 can clear quite early. I would have to check, but it looks to me a lot like WK700 can clear early if the crossover is locked normal and no train is using it and therefore a train can safely approach WK7 at relative speed. If, however, a train is using the crossover, the speed of an approaching train must be controlled on the approach to WK7, lest the train SPAD WK7 at speed and collide with a train on the crossover. Why bother? Why not just move WK7 back so that a train will always stop short of a crossover come what may? Well, because then a train would have to be held further away from Bank than necessary and it would take longer to berth when cleared into the platform. Relevant related reading: LURS. Also a pic from the Video125 film: If I remember rightly, having been part of the SRCC and sighting team, 700s was brought in for 2 reasons, firstly was to regulate the timetable at the time, second was to pre-empt the 5 train service. Without 700s the majority of am/pm trains would be held on approach to Bank. Outside the peaks, it does indeed clear early to 7s as you get a straight green to plat 8 so train speed is high at 40kph over the points, into plat 7 (to run a faster peak service) speed needs to be checked for consecutive policemen set at 15 then 10 kph. at present, the timing section appears to be out of kilter, hence you can see the TO up by starter during the peaks!
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