From: Mortimer on 16 Jul 2010 14:50
"McKevvy" <vicko_zoomba(a)hotmail.com> wrote in message
> On the M8 eastwards the gantry sign read "M8 EAST CLOSED AFTER JCN 4
> WHITBURN". So I prepared to turn off when I approached jcn 4,
> expecting to be forced off by the plods or H.A. with cones and
> flashing lights.
> But nothing was there to stop me or the others so we all kept on
> going. What was after the jcn was a burned out van in the hard
> shoulder of the westbound carriageway which the fire brigade had
> extinguished some time ago.
As I was driving down the M1 and M42 on Sunday, there were several occasions
where I saw "QUEUE - CAUTION" on the matrix signs, followed by successively
reducing advisory speed limits (ie without a red circular border). After two
or three speed limits, the next sign was END. And there was no sign of what
had caused the restrictions: the traffic was as sparse as you'd expect for a
One such occasion, when there was no matrix sign, I saw the lights actually
start: when the first gantry sign was visible in the distance, it was not
lit. As I got closer the amber lights started flashing and the speed limit
was displayed. I could see successive signs after that display 50, 40, 40,
End - and they all came on in unison. So it wasn't a warning that had been
left on after the incident had cleared. Weird.
From: Mortimer on 19 Jul 2010 06:23
"GT" <a(a)b.c> wrote in message
> I have also been totally underwhelmed, if not annoyed by them until a
> recent trip home up the north west of the England. (I think it was the M6)
> as we passed under one of the signs, it started to flash 50mph, but a few
> moments as I approached the next one I could see that it was switched off
> until I got near and it then also started to flash 50. I figured that
> there was a queue building up ahead and they were just switching on the
> signs, but there was actually a slow vehicle up ahead being given
> escorted. As I passed the convoy, I watched the overhead gantry signs
> change again from '50' to 'end' and then I saw the next one switch from
> 'end' to 'blank'. A rolling temporary speed limit. This is the only time I
> have been impressed by them though!
That sounds like a very intelligent use of speed limit signs - better than
turning every sign for miles before (and maybe miles after, in anticipation
that the slow vehicle will get there eventually).
I wish when they put up text signs like "Queue / Incident / Accident ahead"
they'd also say *how far ahead* so you know when to start expecting trouble
and also when you'll be past the restriction. Predicting where the back of
the queue will be is difficult, though I'm sure cameras on the overhead
gantries can monitor the traffic and update the signs as the queue extends
back into the next "block" between one sign and the next. Of course it means
that each sign will display a different distance, so they need to know how
far apart the signs are, but this is basically a software problem. I gather
that the text that is displayed on the signs at present is chosen from a
*preset* list, rather than being free-form, adjusted by the control room to
the precise incident, which seems a naive restriction. Signs which warn of a
restriction which is not apparent for many miles lead to "crying wolf"
problems with people eventually deciding that the restiction must have gone
away, and becoming less vigilent again just as they finally encounter the
I tend to treat recommended speed limits (as opposed to the mandatory
red-ringed ones) as advance warning that there is (probably!) a restriction
ahead, and that I need to keep a careful look out for brake lights and
stationary cars ahead. I do this anyway, but at least I'm forewarned and
will spend a greater proportion of the time looking further ahead. What I
don't do is to immediately slow down to the recommended speed even though
there is clear road for a mile ahead!
The real problem with signs is when they are actually *wrong*. I was once
driving back on the M1 and there were "accident ahead" signs and then the
"lane 3 closed" sign. Everyone duly moved over into Lanes 1 and 2 in
anticipation. Sadly it was both Lanes 2 and 3 which were coned off and the
police were directing traffic onto the hard should and Lane 1. If they'd
only signed it as "Lanes 2 and 3 closed", people could have got into Lane 1
(and maybe the hard shoulder if "use hard shoulder signs" could be
displayed) in advance rather than having to do so once all the traffic was
stationary. The queue woudl have been much shorter if they'd done that.