Blue railway signals?

People with colour blindness shouldn't drive trains (or cars for that matter).

And it's not very many, in fact I know of only one person who's colourblind.


On Fri, 14 Dec 2018 09:07:18 -0000, Brian Gaff wrote:

Yes I think that is where the confusion came from actually. So many people
have colour blindness that blue is normally avoided.

Brian

On Fri, 14 Dec 2018 08:45:09 -0000, The Natural Philosopher wrote:

On 13/12/2018 16:57, Steve Walker wrote:
On 13/12/2018 16:42, Fred Johnson wrote:
Can anybody else remember blue traffic lights on railways? Can't find
any evidence on google. I'm sure whereas cars have red/amber/green,
railways always had a 4th blue light. What does it mean and why has
it disappeared from Google?

Never heard of it.

4 (& 5)-aspect signals have always had red, green and two ambers as far
as I know.

I know that the semaphore signals had lenses that were red and blue, but
they definitely showed as red and green when lit from behind by
yellowish oil lamps at night.

SteveW

No, Blue was never part of railway standard signals. I am very hazy but
ISTR two amber - sequnec being green-two amer - one amber - red as the
obstruction was approached..

ISTR blue was something one saw on te railways but it wasn't part of the
standard signals

Yes it was probably a light for something else I saw. Google refers to it being used for tunnels etc. Mainly for markers to show where an edge is (not sure why a train needs to know that, after all they can't be steered....)

On Fri, 14 Dec 2018 00:38:25 -0000, Steve Walker wrote:

On 13/12/2018 19:40, Fred Johnson wrote:
On Thu, 13 Dec 2018 17:40:20 -0000, Rod Speed
wrote:

Fred Johnson wrote

Can anybody else remember blue traffic lights on railways?
Can't find any evidence on google. I'm sure whereas cars
have red/amber/green, railways always had a 4th blue light.
What does it mean

https://en.wikipedia.org/wiki/Railwa...nal#Components

and why has it disappeared from Google?

It hasn't.

Blue lights are not mentioned in that link.

BTW, something in the link reminded me of a local accident where the
railways had managed to install an overhead gantry of some sort
obstructing the view of some lights, so the driver didn't stop.
M'colleague took some photos from the driver's cabin of another train as
it went on the same route and proved his innocence (as part of his
psychology work I think). There's something wrong in the world when a
3rd party has to prove your innocence.

The Ladbroke Grove rail crash, signal SN109?

That's the one. M'colleague (Professor Roger Watt) discovered the sunlight reflected from the lights at that time of day. I thought he'd said it was a gantry in the way, but it was a long time ago. I could be remembering something he'd said before completing the inquiry.

On Fri, 14 Dec 2018 11:45:18 -0000, JNugent wrote:

On 14/12/2018 11:33, Nightjar wrote:
On 14/12/2018 09:27, Rod Speed wrote:
Nightjar wrote
Fred Johnson wrote

I wonder why the red is at the bottom on rail lights and the top on
traffic lights?

On railways it is at the bottom so that there is no light shade below
it, on which snow could build up and obscure the light.

So why didn't that continue with street lights ?

Perhaps the American who invented them hadn't thought about that
problem. Overground railway light signals were not standardised until
rather later - in 1924.

I have never seen a set of road traffic lights obscured by built-up
snow, not even during the worst of UK blizzards. Has anyone else?

Not me.

The next question is why. Perhaps bulbs create enough heat to melt it. I wonder if LEDs will bring the problem back?

On Fri, 14 Dec 2018 11:23:26 -0000, Max Demian wrote:

On 14/12/2018 00:47, Steve Walker wrote:
On 13/12/2018 23:12, Rod Speed wrote:


"Fred Johnson" wrote in message
news On Thu, 13 Dec 2018 21:03:57 -0000, Mike Humphrey
wrote:

Fred Johnson wrote:

Can anybody else remember blue traffic lights on railways? Can't
find any evidence on google. I'm sure whereas cars have
red/amber/green, railways always had a 4th blue light. What does
it mean and why has it disappeared from Google?

Railway signals in modern times have always had red, yellow (not
amber)

I've never been fussy enough to even notice the difference between
yellow, amber, orange. I could tell the difference if they were side
by side, but I just think of a road traffic light as either yellow or
orange. I couldn't even tell you what amber colour is compared to
yellow and orange. I don't do things like "mauve", etc. Just purple,
light purple, etc.

and green. A four-aspect signal has two yellows - the sequence
approaching a stop signal goes G, YY, Y, R. There can be a number of
other indications as well as the main signal but these are almost
invariably white.

I assume this is to allow trains the longer stopping distance they
require than road vehicles.

There's a number of uses for blue and purple, but not appearing with
the
R/Y/G "traffic light" signals, at least in the UK.

I might be thinking of non "traffic light" signals, or I might be
thinking of a light which was off and was just seeing the blue lens
which had a yellow light behind to make green.

If you want to look
at the full range of signs and signals, http://www.railsigns.uk/ has a
very comprehensive guide.

That's a lot for a driver to remember! At least with road signs the
symbol is meaningful.

I wonder why the red is at the bottom on rail lights and the top on
traffic lights?

Basically because when there are two ways of doing
something, you can be sure someone will do it both ways.

I am sure that I remember reading that it was based upon upper-quadrant
semaphore signalling, where a raised signal was "off" (clear) and
horizontal one was "on" (danger). Although both upper and lower quadrant
signals were used in the UK, they were almost all UQ (except on GWR
lines) from the 1920s - with the advantage that broken cables or heavy
snow caused them to drop to danger rather than the clear of LQ ones.
They simply copied UQ practice, so the top was clear and the bottom danger.

Yebbut with semaphore signals the light is always in the same position.

But the lack of a red light is in a different position.

On 14/12/2018 18:22, Fred Johnson wrote:
People with colour blindness shouldn't drive trains (or cars for that
matter).

And it's not very many, in fact I know of only one person who's
colourblind.

It matter for railways due to needing to determine the colour from a
long distance, due to the long stopping distance of a train. It is fine
for a colourblind person to drive a car, as the stopping distance is
short enough for the driver to get close enough to determint the
position of the light on traffic light.

Up to eight percent of men of North European decent are red-green colour
blind.

SteveW

On 14/12/2018 11:23, Max Demian wrote:
On 14/12/2018 00:47, Steve Walker wrote:
On 13/12/2018 23:12, Rod Speed wrote:


"Fred Johnson" wrote in message
news On Thu, 13 Dec 2018 21:03:57 -0000, Mike Humphrey
wrote:

Fred Johnson wrote:

Can anybody else remember blue traffic lights on railways?* Can't
find any evidence on google.* I'm sure whereas cars have
red/amber/green, railways always had a 4th blue light.* What does
it mean and why has it disappeared from Google?

Railway signals in modern times have always had red, yellow (not
amber)

I've never been fussy enough to even notice the difference between
yellow, amber, orange.* I could tell the difference if they were
side by side, but I just think of a road traffic light as either
yellow or orange.* I couldn't even tell you what amber colour is
compared to yellow and orange. I don't do things like "mauve", etc.
Just purple, light purple, etc.

and green. A four-aspect signal has two yellows - the sequence
approaching a stop signal goes G, YY, Y, R. There can be a number of
other indications as well as the main signal but these are almost
invariably white.

I assume this is to allow trains the longer stopping distance they
require than road vehicles.

There's a number of uses for blue and purple, but not appearing
with the
R/Y/G "traffic light" signals, at least in the UK.

I might be thinking of non "traffic light" signals, or I might be
thinking of a light which was off and was just seeing the blue lens
which had a yellow light behind to make green.

If you want to look
at the full range of signs and signals, http://www.railsigns.uk/ has a
very comprehensive guide.

That's a lot for a driver to remember!* At least with road signs the
symbol is meaningful.

I wonder why the red is at the bottom on rail lights and the top on
traffic lights?

Basically because when there are two ways of doing
something, you can be sure someone will do it both ways.

I am sure that I remember reading that it was based upon
upper-quadrant semaphore signalling, where a raised signal was "off"
(clear) and horizontal one was "on" (danger). Although both upper and
lower quadrant signals were used in the UK, they were almost all UQ
(except on GWR lines) from the 1920s - with the advantage that broken
cables or heavy snow caused them to drop to danger rather than the
clear of LQ ones. They simply copied UQ practice, so the top was clear
and the bottom danger.

Yebbut with semaphore signals the light is always in the same position.

But the light is not used in daylight, only the arm is, hence light only
signals copying the arm position.

SteveW

On Fri, 14 Dec 2018 22:59:29 +0000, Steve ******, the notorious,
troll-feeding, senile idiot, blathered again:


It matter for railways due to needing to determine the colour from a

The ONLY thing that matters to the Scottish troll is whether or not he gets
some senile idiot to suck him off! And he is ALWAYS successful with YOU,
Steve ******! tsk

On 14/12/2018 00:59, Rod Speed wrote:


"Steve Walker" wrote in message
news
On 13/12/2018 23:12, Rod Speed wrote:


"Fred Johnson" wrote in message
news On Thu, 13 Dec 2018 21:03:57 -0000, Mike Humphrey
wrote:

Fred Johnson wrote:

Can anybody else remember blue traffic lights on railways?* Can't
find any evidence on google.* I'm sure whereas cars have
red/amber/green, railways always had a 4th blue light.* What does
it mean and why has it disappeared from Google?

Railway signals in modern times have always had red, yellow (not
amber)

I've never been fussy enough to even notice the difference between
yellow, amber, orange.* I could tell the difference if they were
side by side, but I just think of a road traffic light as either
yellow or orange.* I couldn't even tell you what amber colour is
compared to yellow and orange. I don't do things like "mauve", etc.
Just purple, light purple, etc.

and green. A four-aspect signal has two yellows - the sequence
approaching a stop signal goes G, YY, Y, R. There can be a number of
other indications as well as the main signal but these are almost
invariably white.

I assume this is to allow trains the longer stopping distance they
require than road vehicles.

There's a number of uses for blue and purple, but not appearing
with the
R/Y/G "traffic light" signals, at least in the UK.

I might be thinking of non "traffic light" signals, or I might be
thinking of a light which was off and was just seeing the blue lens
which had a yellow light behind to make green.

If you want to look
at the full range of signs and signals, http://www.railsigns.uk/ has a
very comprehensive guide.

That's a lot for a driver to remember!* At least with road signs the
symbol is meaningful.

I wonder why the red is at the bottom on rail lights and the top on
traffic lights?

Basically because when there are two ways of doing
something, you can be sure someone will do it both ways.

I am sure that I remember reading that it was based upon
upper-quadrant semaphore signalling, where a raised signal was "off"
(clear) and horizontal one was "on" (danger). Although both upper and
lower quadrant signals were used in the UK, they were almost all UQ
(except on GWR lines) from the 1920s - with the advantage that broken
cables or heavy snow caused them to drop to danger rather than the
clear of LQ ones. They simply copied UQ practice, so the top was clear
and the bottom danger.

That doesn't explain why street traffic lights reversed the order with
just lights.

Because there was no standardisation of railway signals in the early
years, so copying railway practice could just as easily lead to the
opposite system.

The long mechanical operating systems needed on railways later lead to
preferring the safer failure mode of upper quadrant signals rather than
the alternative lower quadrant ones. Such mechanisms were absent from
road traffic signals.

SteveW

Steve Walker wrote:


I am sure that I remember reading that it was based upon upper-quadrant
semaphore signalling, where a raised signal was "off" (clear) and
horizontal one was "on" (danger). Although both upper and lower quadrant
signals were used in the UK, they were almost all UQ (except on GWR
lines) from the 1920s

The odd lower quadrant is still Installed in former(original)GWR territory
if the track layout needs altering though their tenure will be short lived
as more modern signal schemes eliminate the old signal boxes.
Rumour says that back in the 1960’s when an edict was issued that
installations should be of the BR upper Quadrant style someone on the
Western Region determined to uphold the tradition that the GWR /WR was
always different quickly ordered enough GWR style components that they had
enough to last for 40 years.
This one at Truro a was installed about 8 years ago and uses a mixture of
the old GWR components and more modern parts.

GH