Great Western Coffee Shop

Whilst waiting on Guildford station yesterday, I noticed the signal at the end of one of the platforms (platform 2 for the interested) was showing a flashing double-amber.  What does this mean and how is it different from a standard double-amber? 

Thanks

A single yellow flashing signal would follow it, and it means that the signal after that is showing a 'proceed' aspect at a diverging junction for the highest speed diverging route.  Basically it's a way of ensuring trains go through the section as quickly as possible (a similar method is the splitting distant colour light signals at various locations).  The driver is aware he will be leaving the main line and needs to adjust his speed accordingly, but that the route is set for that move.

See: http://www.rgsonline.co.uk/Rule_Book/Rule%20Book%20Modules/S%20-%20Signals/GERT8000-S1%20Iss%201.pdf (http://www.rgsonline.co.uk/Rule_Book/Rule%20Book%20Modules/S%20-%20Signals/GERT8000-S1%20Iss%201.pdf) pages 9-12 for more details.

Hate to contradict you II but a flashing double amber would indicate that the route ahead is set for a speed lower than that of the main route.
From the rule book module you quoted:

2.5 Four-aspect flashing yellow signalling
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.

Sure it was just a typo!  ;)

No problem.  My explanation may have not been too clear.  When I said 'Highest speed diverging route' I meant aside from the main route straight ahead.

So, if the route ahead is 100mph and there is a 70mph route over a crossover and a 50mph route over a crossover that are controlled from the same signal, then you could have flashing yellows for the 70mph route, but not the 50mph one, which would have to be approach controlled like most junctions.

Please note that on the railways the term used is yellow not amber.

I think the rail staff posting above had already made that point, somewhat more politely.

Anyway, as well as flashing single/double yellow aspects, flashing greens and (sort of) flashing reds also exist. Flashing greens are used on the East Coast Mainline (and maybe elsewhere, I don't know) as a kind of "super green" aspect, indicating that the next signal will be showing either a steady or flashing green aspect.

And there are SPAD indicators dotted around the place which are normally not illuminated show a steady red flanked by flashing red aspects above and below (meaning "hold it right there, sunshine!") if the signal immediately before them is passed at danger. They're fitted at places where it is reckoned that a SPAD could have serious consequences, for example a junction. You can see one such at the country end of platform 4 at Reading, which I believe applies to the down starter signal on platform 4, or is it one of the bay platform starters? A while since I've seen it so I can't remember!

Sorry if it appeared rude, I certainly didn't intend it that way.

Ha ha,  as the grandson of someone who was responsible for signalling on the Great Western, I really should've known better than to call a signal amber.  Thanks all for your contributions though. I feel suitably enlightened.

You are correct it is for the starting signal from platform 4 - in fact there are two of them about 50m apart for the same signal.

Re flashing yellows.

I beleive the ones at Paddington have been taken out when the new signal heads were installed and the spped limit imposed after Ladbroke Grove.

Also confusion over which junction the flashing applied was the cause of the Colwich crash.

The flashes were for the Main to Slow Junction and not the following one to Stoke. The driver thought he was clear over the Stoke Junction and couldn't stop when he saw the red Junction Signal.

Yep, there's no 'flashers' at Paddington.  The nearest are for the 70mph junction east of Ealing Broadway from the DR to DM or UM to UR.

  Flashing red's exist at level crossings such as Cookham and Furze Platt where the proceed is a white light.

.......... and who said signaling was easy :P