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| Mainline or position light signal from a siding 09/08/2012 at 17:39 #34799 | |
John
884 posts |
Does anyone know what criteria determines whether the exit from a yard or siding is controlled by a mainline or position light signal? The north end of Letchworth CS, for example, is controlled by a mainline signal - whereas the south end is controlled by a position light. Log in to reply |
| Mainline or position light signal from a siding 09/08/2012 at 17:52 #34800 | |
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Stephen Fulcher
2078 posts 
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There are probably numerous factors which could apply to either being used. Firefly would be the expert on the standards concerned. Log in to reply |
| Mainline or position light signal from a siding 09/08/2012 at 21:33 #34806 | |
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Firefly
521 posts |
Without trawling through the standards it's mainly about operational flexibility. If a train leaves a yard on a shunt signal it must proceed at caution until the next main signal. (I believe this is generally about 15mph because they must be prepared to stop short of any obstruction). If the next signal happens to be 3 miles down the track it would create a bit of a blockage! Trains leaving at the North End of Letchworth will most likely be proceeding towards Baldock and I would guess 955 signal is someway down the line. By having a main signal trains can proceed at linespeed as soon as their tail end has cleared the pointwork. Trains leaving to the south will be straight into the station where 944 signal will give them the authority to proceed at linespeed. Obviously if the move is a passenger move then it must also be a main signal. Hope this helps FF Log in to reply The following user said thank you: John |
| Mainline or position light signal from a siding 09/08/2012 at 21:44 #34807 | |
jc92
3685 posts |
" said:as with signal 1349 at kemble siding "We don't stop camborne wednesdays" Log in to reply |
| Mainline or position light signal from a siding 09/08/2012 at 21:45 #34808 | |
Splodge
716 posts
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In the case of Letchworth, I seem to recall a discussion on here regarding a passenger train that served the carriage sidings - assuming it travelled towards Cambridge it may explain why the signal needs to be suitable for main line running? I could be imagining things, mind! :whistle: There's the right way, the wrong way and the railway. Log in to reply |
| Mainline or position light signal from a siding 09/08/2012 at 21:59 #34809 | |
Steamer
3984 posts
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2R01 does indeed go via Letchworth C.S. (you might have to set Open TT to 'Detailed' mode) Forum topic here. "Don't stress/ relax/ let life roll off your backs./ Except for death and paying taxes/ everything in life.../ is only for now." (Avenue Q) Log in to reply |
| Mainline or position light signal from a siding 09/08/2012 at 22:01 #34810 | |
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Firefly
521 posts |
There's no main class signal route into the Carriage Sidings so trains with passengers on would not be allowed to enter sidings. The only way to get into the sidings is via a shunt class route which are for non-passenger traffic. I would assume they make an exception for staff trains since they are not carrying fare paying passengers Last edited: 09/08/2012 at 22:04 by Firefly Log in to reply |
| Mainline or position light signal from a siding 09/08/2012 at 23:02 #34812 | |
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Underwood
748 posts |
I don't think 2R01 is even for passengers, as I once tried to use this having seen it in Open Train Times and Kings Cross station wasn't even open! I did try finding tickets for it after and, with having just double checked, no such service shows up on a journey search anyway. 2R01 is more likely a staff train, which is what I guessed with it going via the A/D line, and I believe a few of these can run under class 2 headcodes, otherwise class 5 codes? Log in to reply |
| Mainline or position light signal from a siding 10/08/2012 at 15:55 #34819 | |
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metcontrol
227 posts |
With regard to Letchworth - Signal K948 (up) is quite a distance from the platforms at Letchworth (despite it looking as though its at the station on Simsig.) Signal K955 approaching Baldock is probably just under twice this same distance (K953 / K951 sit around halfway to Baldock). Trains from the sidings towards Baldock rarely begin to resume line speed before reaching K955, so I wonder if it is usual practice to show just a single yellow on K951. The only reasoning I can think of is that from the south/up end of the sidings, trains can be shunted/called-on into the platforms, including when occupied, whereas such moves are not carried out at the north/down end. I suppose technically both ends could be equipped with both types of signal, but to avoid unnecessary costs it was chosen just to equip with signals that serve the main purpose. Log in to reply |