Sorry, what I meant was if drivers were to treat them as if they were triple yellows and to expect a double yellow ahead.It meant to run at 125mph didn't it? If it slows them from 140mph to 125mph then yes it is somewhat restrictive.
Sorry, what I meant was if drivers were to treat them as if they were triple yellows and to expect a double yellow ahead.
Sent from my Nexus 4 using Tapatalk
No, with the five aspect signalling system, you should expect to see either double flashing greens or a single green aspect ahead, if you see the single green aspect ahead, you drop the speed to 125mph.
That's what green signals, in 4 aspect areas, always signify! So it's no different in that respect. If a driver sees a green in a 4 aspect area, then it means that the next 3 blocks are clear.Sorry, what I meant was if drivers were to treat them as if they were triple yellows and to expect a double yellow ahead.
Yes it is.Isn't the discussion a bit irrelevant as the safety authorities have decided that you can't exceed 125 mph without cab signalling.
Class 91s need the extra distance to brake comfortably from 140mph to a stand but what about Pendolinos?
Could they come to a stand upon seeing a double yellow at 140mph to the red two signals later and comfortably?
Class 91s need the extra distance to brake comfortably from 140mph to a stand but what about Pendolinos?
Could they come to a stand upon seeing a double yellow at 140mph to the red two signals later and comfortably?
Interesting. In my head I always thought a green means "Expect a green but be prepared for double-yellow".That's what green signals, in 4 aspect areas, always signify! So it's no different in that respect.Sorry, what I meant was if drivers were to treat them as if they were triple yellows and to expect a double yellow ahead.
In my head I always thought a green means "Expect a green but be prepared for double-yellow".
Yeah, I can see the logic there, but if you're expecting a cautionary aspect would you open the taps after when the line speed increases after passing a green? I suppose I'm reading too much into the word 'expect'.Goodness me, no. Telling drivers to "expect a green" at a signal that might be displaying a caution aspect would be asking for trouble.
Yeah, I can see the logic there, but if you're expecting a cautionary aspect would you open the taps after when the line speed increases after passing a green?
Class 91s need the extra distance to brake comfortably from 140mph to a stand but what about Pendolinos?
Could they come to a stand upon seeing a double yellow at 140mph to the red two signals later and comfortably?
Just a thought that'd been niggling away for a while - how's that work at, say, Woolmer Green Jn where a green on the Up Slow (3-aspect signal protecting the junction) can read to a single yellow (in a 4-aspect sequence if approached from the Up Fast), which would then give inadequate braking distance to the red if a train off the slow was able to accelerate to (nearly) linespeed before sighting the yellow? Is there an assumption made about the best possible acceleration characteristics in this sort of case?Yes, why not? The next signal beyond the permissible speed increase would have to be spaced at full braking distance - from the higher speed - to the relevant stop signal (two signals ahead in 4-aspect territory).
Just a thought that'd been niggling away for a while - how's that work at, say, Woolmer Green Jn where a green on the Up Slow (3-aspect signal protecting the junction) can read to a single yellow (in a 4-aspect sequence if approached from the Up Fast), which would then give inadequate braking distance to the red if a train off the slow was able to accelerate to (nearly) linespeed before sighting the yellow? Is there an assumption made about the best possible acceleration characteristics in this sort of case?
Thanks, makes perfect sense. That specific concept seems to be widely misunderstood though, I must say!Yes; in that sort of situation, braking distance can be based on attainable speed.
Thanks. Seems obvious now that you've explained it.Yes; in that sort of situation, braking distance can be based on attainable speed.
On a vaguely related theme there are a couple of signals with flashing reds near Hucknall on the robin hood line. They seem to be associated with LCs shared with trams. Anyone here know what the flashing aspect means?
IIRC flashing reds on the approach to an ABCL or AOCL crossing mean the crossing equipment is active but not triggered. When the sequence is running it changes to flashing white.
Just a thought that'd been niggling away for a while - how's that work at, say, Woolmer Green Jn where a green on the Up Slow (3-aspect signal protecting the junction) can read to a single yellow (in a 4-aspect sequence if approached from the Up Fast), which would then give inadequate braking distance to the red if a train off the slow was able to accelerate to (nearly) linespeed before sighting the yellow? Is there an assumption made about the best possible acceleration characteristics in this sort of case?
I am not expert on this - but...
My impression is that you are suggesting that a train approaching the junction might get a green and then, instead of getting further greens through the junction, the route might be changed with the result that the next signal had become a single yellow on approach with a red beyond it protecting the junction.
Would that be a correct interpretation?
If so - it would seem to me to be the equivalent of an old style signalman allowing a train to approach with the Distant "Off" and then putting back in order to change the route through the junction. This was absolutely not allowed! If a change had to be made a train on clear signals had to be allowed to run clear or brought to a dead stand before the junction route was unlocked.
I would expect that something very similar would apply with all colour light/TCB signalling. The interlocking would, I think, prevent a green onto single yellow - or at least, it would hold the route in a similar way to the above.
Put another way - a train passing a signal at green shouldn't get a single yellow next - except with an emergency or fault put-back...
Am I basically correct about the interlocking please?
Thanks
Just a thought that'd been niggling away for a while - how's that work at, say, Woolmer Green Jn where a green on the Up Slow (3-aspect signal protecting the junction) can read to a single yellow (in a 4-aspect sequence if approached from the Up Fast), which would then give inadequate braking distance to the red if a train off the slow was able to accelerate to (nearly) linespeed before sighting the yellow? Is there an assumption made about the best possible acceleration characteristics in this sort of case?
Sectional Appendix said:LN101 - KINGS CROSS TO SHAFTHOLME JN
New England North To Stoke Tunnel
Flashing green signal aspects for special test runs
In connection with special test runs the following arrangements will apply :-
1. Use of Flashing Green Main Signal Aspects
1.1 Flashing Green aspects (in addition to steady green aspects) have been provided on the:-
a) Down Fast line between Signal P487 (north of New England North) and P6l5 (approaching Stoke).
b) Up Fast line between Signal P610 (South of Stoke) and Signal P494 (south of Werrington Jn).
The meaning of a flashing green aspect is next signal exhibiting a steady or flashing green aspect.
The AWS will give a bell for both flashing and steady green aspects.
1.2 Drivers of all trains except test trains which are authorised to exceed 125 m.p.h., must treat flashing green aspects the same as steady green aspects.
1.3 Drivers of test trains authorised to exceed 125 m.p.h., must treat:-
a) a flashing green aspect as authority to exceed 125 m.p.h.
b) a steady green aspect as authority to proceed at or a requirement to reduce speed to 125 m.p.h.
2. Staff Safety
A special notice to staff will be issued when trains are authorised to exceed 125 m.p.h.
Dated: 02/12/06
. . . . and just in case anyone here wasn't aware, they are still operational between Werrington and Stoke.Returning to the topic of flashing greens, it's worth noting that they're still mentioned in Module LN2 of the London North Eastern Sectional Appendix, . . . .
From what I gathered from Philip Phlopp the 225 sets can stop from 140mph from a double yellow comfortably, the issue is passenger comfort as it would be severe braking. I doubt Pendolinos would be any different in that regard.
1.3 Drivers of test trains authorised to exceed 125 m.p.h., must treat:-
a) a flashing green aspect as authority to exceed 125 m.p.h.
b) a steady green aspect as authority to proceed at or a requirement to reduce speed to 125 m.p.h.