Indeed...presumably this is a relatively high speed divergance, and this, combined with the frequency of Metro services, means that 'standard' approach control would cause too many delays.tramboy said:That clears up what had been bothering me about the T+W Metro then, as one of the most common places to see this is from the front of a Tyne and Wear metrocar when you are approaching Pelaw Metro Junction (where Metro goes back to South Gosforth control and not Newcastle IECC).
I noticed that when up at newcastle last week. I wondered what on earth it meant until we came to the junction. There's a case of this in KX Simsig north of Welwyn North too I believe.tramboy said:That clears up what had been bothering me about the T+W Metro then, as one of the most common places to see this is from the front of a Tyne and Wear metrocar when you are approaching Pelaw Metro Junction (where Metro goes back to South Gosforth control and not Newcastle IECC)
Sorry to drag this up from the depths, but the Rule Book has this different. It says:Craig said:It means the next signal will be set for the highest speed diverging route.
one TN[/quote]A flashing yellow aspect means that the facing points at a junction ahead are set for a diverging route, over which the speed of the train must be reduced.
Westerleigh Junction is 30mph UP and DOWN on the Birmingham line due to the sharp turn off of the Junction. However currently there is a 20mph TSR.Mojo said:I know it is very low, and although I don't pay much attention, I did see a 30mph sign to the south of Yate station. Whilst that may be part of a gradual slowdown for the junction, or the actual speed the junction should be taken at, I don't know.
It is not approach controlled id assume, because if it was it would cause too much delay as the Bristol PW - Westerleigh section is quite heavily used by the London Trains, North-bound trains, Locals and not forgetting Freight traffic from Avonmouth, Wales, Bristol and the south-west.Tomnick said:Not disputing that there's flashing yellows at Westerleigh (Simsig shows them too ), but are you sure that the PSR over the diverging route is as low as 20mph? If that was the case, I'd have thought that approach control from red would have been preferred! I know there's quite a few exceptions, but flashing yellow junction signalling was originally intended for locations where approach control from red would be too restrictive, for example a 50-60mph turnout on a 90mph line.
The choice (Flashing-Approach control) depends on various things...dvn1357 said:Is this always the case, looking on Exeter Simsig, there is no flashing amber from DML > Down Torbay where the line speed drops from 60>40, which is 2/3 although it appears to use conventional approach control! Unless this is a fault with Simsig?
Sorry, but as others have dragged this one up I feel I must correct something.yorkie said:It is much better for trains to use flashing yellow junctions as they only have to slow down for the junction and take it at full line speed. Where approach from red is used trains often have to slow down a considerable distance before the junction.
Sorry, but that's incorrect. The first signal on the diverging route is not held at red - the junction signal might *imply* a red but it doesn't mean there *is* a red. Of course, local conditions might require it to be red at the time (another train in front, a controlled signal with no route set, etc), but this is not usually the case.one TN said:and a red at the first signal on the diverging route.
Feathers are normally used when it is approach control, ie, the train must treat the signal as a permanant danger (not going to clear in time) until it clears when the train occupies a track circuit closer to the signal, normally between the AWS magnet and the signal head, where as flashing cautions are used to keep the speed up until after the junction, meaning you can get more trains over the junction in the same space of timeJoe H said:Why are flashing yellows used instead of feathers?