Semaphore distants - speed signals?

[Annetts key]

So if a distant is not a speed signal, it does not tell the driver to control their speed? <wink> A distant is unrelated to line speed <further wink>

Yes, yes - you can say it means "expect stop", but how else can you stop if not by controlling your speed?

Compare a heavy freight train with a very modern passenger train that has the latest braking system.

Generally speaking, as soon as the driver of the freight train sees the distant in the caution position (a yellow aspect in a colour light signal) they will apply the brakes. Often gently at first. But increasingly and quickly moving to the full service brake position.

Now, the driver of the very modern passenger knows that they can stop a lot faster than the freight train, so they may just coast for a short while, then apply the brakes.

So potentially for ¼ to ½ a mile, the two trains will be travelling at very different speeds after passing the distant signal. But both will be able to stop without passing the stop signal.

 

[30907]

So if a distant is not a speed signal, it does not tell the driver to control their speed? <wink> A distant is unrelated to line speed <further wink>

Yes, yes - you can say it means "expect stop", but how else can you stop if not by controlling your speed?

But a speed signal is something else - it typically instructs the driver to travel at no more than X (or 10X) km/h from that point, where X is variable, rather than to reduce speed towards zero at a location ahead.

The nearest analogy I can come up with is the overhead signs on smart motorways, which apply from that point - whereas a distant is like an advance warning of roadworks with a (50) speed limit.

 

[12LDA28C]

A Distant signal does NOT inform the driver of a speed restriction! It warns him of the aspect of the following Home signal.
As has been said several times.

Indeed - or any associated stop signal controlled by the same signalbox in that direction of travel.

There is some utter rubbish being spouted on this thread I'm afraid.

So if a distant is not a speed signal, it does not tell the driver to control their speed? <wink> A distant is unrelated to line speed <further wink>

Yes, yes - you can say it means "expect stop", but how else can you stop if not by controlling your speed?

By your definition, it appears any kind of restrictive aspect is a 'speed signal'.

 

[edwin_m]

So if a distant is not a speed signal, it does not tell the driver to control their speed? <wink> A distant is unrelated to line speed <further wink>

Yes, yes - you can say it means "expect stop", but how else can you stop if not by controlling your speed?

On that definition, all signals are speed signals, so the terminology becomes redundant.

I guess a definition of speed signalling would be where the signal aspect conveys to the driver an instruction not to exceed a specific speed. The most obvious ones (in Germany, probably elsewhere) have illuminated digits giving the permitted speed in multiples of 10km/h.

 

[Railsigns]

Deleted.

 

[Rescars]

Are there still semaphore distants at Worcester Shrub Hill? IIRC these are/were fixed because of the speed restrictions which apply around the curves of the triangle. I am sure I have seen it mentioned that it was GWR practice to fix distants on lines with a speed restriction of 40 mph or less. So not speed signals as such, but a situation in which speed was a factor in determining the type of signal to be used.

 

[Tomnick]

I think a distant only covers multiple stop signals in absolute block ( but you'd still be expected to be able to stop at the first one anyway ). Are there non-AB semaphores around?

I guess approach release might be thought of as speed signalling, but ...semaphore?

There's no distinction between AB and non-AB in this context. It's "all associated stop signals" either way.

There's a "textbook" semaphore layout (distant-home-starter both ways) at Swinderby, which works TCB in both directions. There's other examples at AB/TCB fringe boxes too, e.g. Manea, where you're under TCB regs at the distant.

 

[king_walnut]

There are distant signals on my route where I will still be doing line speed for a little while if they're on.

 

[Ashley Hill]

I am sure I have seen it mentioned that it was GWR practice to fix distants on lines with a speed restriction of 40 mph or less

St Blazey has its fixed semaphore distant signal underneath Par’s down branch advanced starter. As it belongs to St Blazey will it survive the abolition of Par box later this year

 

[Efini92]

I have heard it claimed (by someone who claims to know what they're talking about) that UK semaphore distants are speed signals, because 1) they cover multiple stop signals, any one of which being at stop places the distant at caution, and 2) a distant may be at caution even if no stop signals are at stop, e.g. when a train is being routed to a slower diverging route. Thus the argument is that a UK distant is not a block signal and conveys no information to the driver besides "slow down". Is there any truth to this argument?

You’ve got it the wrong way round. A semaphore distant is the most import signal. It tells the driver wether the signals associated with it are on or off.

 

[Tomnick]

St Blazey has its fixed semaphore distant signal underneath Par’s down branch advanced starter. As it belongs to St Blazey will it survive the abolition of Par box later this year

Unlikely. It'd possibly be replaced by a colour-light signal capable of showing R/Y only. It's perhaps more likely that there'll be more wider changes at St Blazey to accommodate the fringe to TCB

 

[Railsigns]

St Blazey has its fixed semaphore distant signal underneath Par’s down branch advanced starter. As it belongs to St Blazey will it survive the abolition of Par box later this year

The scheme plan shows it being abolished.

 

[Ken H]

Does a route indicator or a splitting distant convey a speed? The driver will know the speed by his route knowledge, augmented by speed restriction signs.

Hellifield has a semaphore distant on the line from clitheroe.

 

[Steveswan10]

Dorrington, Marshbrook, Craven Arms, Bromfield and Woofferton are all semaphore home with colour light distant.
I think the rest of the Boxes down the Marches are the same.
Onibury, in the middle, is all colour light.

Leominster is colour light distant with semaphore home and section signal on the down main only-the up main is colour Light distant, home and section, Moreton on lugg is now fully colour light as is Tram Inn, Pontrilas and Abergavenny are still semaphore and (I assume) colour light distant

 

[12LDA28C]

Does a route indicator or a splitting distant convey a speed? The driver will know the speed by his route knowledge, augmented by speed restriction signs.

No. As you say the driver's route knowledge would determine his braking.

 

[Irascible]

And to those people talking of 'approach release' signals - I'd get my arse kicked in a Rules exam for saying that. The correct terminology would be 'approach controlled'. You should never expect the signal to come off and instead, be prepared to stop.

Oops, mea culpa, it's been a long time. I can see where the *system* might be thought of as "speed signalling" ( it is not, the usage is as a side-effect ) but that doesn't make a signal a speed signal any more than the semaphore distant in the OP.

There's no distinction between AB and non-AB in this context. It's "all associated stop signals" either way.

I wanted the distinction because I wanted to know about non-traditional-AB installs. Thanks for providing a couple, I'll have a look.

 

[edwin_m]

Aside from that, replacing a semaphore distant signal with a colour light equivalent is relatively straightforward, whereas doing the same with semaphore stop signals can throw up all sorts of issues.

In particular, a semaphore stop signal can't be replaced by a red/green colour light unless it's the section signal and there is a distant protecting the next stop signal. A green colour light is an unrestricted proceed aspect and can't be followed by a stop signal at danger. Instead, a three-aspect has to be used, clearing only to single yellow if the next stop signal is at danger. Usually this doesn't have braking distance to the next stop signal, in which case the distant must also remain at caution.