Variable speed limits - Thommo
Traveling around the M25 last night, anti-clockwise just past the M40 junction, there had clearly been an incident some time before but the road was now clearish and free flowing. However the overhead signs still indicated a 40 limit.

So being the cautious type I got over to the inside lane and passed the sign at 40, much to the annoyance of the guy behind me who was poddling along at 60 and had to overtake for probably the first time in his life. Across the other four lanes the average speed was roughly 75/80.

Now question, given that the road was clear and the signs had just not been switched off, are these guys (assuming the camera was working properly) going to get done? The guys doing 80 being 40 over the posted limit must be in instant ban territory must they not?
Variable speed limits - CM
The M25 variable speed limits are also there to prevent jams building up and are not in place when a jam already exists (ie proactvie rather than reactive). The reasoning behind this is to prevent the stop start traffic that blights our m-ways (and for the life of me I cannot understand them but presume it is the principle that creates phantom jams).

Also i belive that all of the gantries have cameras in them and that they are fairly active.
Variable speed limits - Thommo
The phenomena is called compression waving.

I take you point about proactive, but the M25 was clear and fast flowing from that point through to J10 where I got off, so I still suspect that they just had not been turned off after an ealier incident.

Variable speed limits - Steve S
Thommo,

By and large people seem to observe the 60 or 50 limit that is often posted to try to smooth the flow at times of congestion. So the camera situation probably doesn't arise.

But the situation you describe I've seen many times. The sheer volume of vehicles that ignored them leads me to believe they can't be being snapped by cameras.
Variable speed limits - peterb
The powers that be a very slow at resetting variable limits.

I was on the M40 the other day at 11.30 pm and making good progress. The LEDs on the central reservations started flashing a 60 mph limit and then 40 mph. The reason was a lane closure and whilst I'm sure compression waving was necessary in the rush hour, it wasn't in the middle of the night!
Variable speed limits - Altea Ego
I make this journey late at night once a week. For the past couple of months there has been work goin on at night on the M25 southbound/M4 slip. They turn on the warning lights from the M40 juntion onwards. There is only one camera gantry southbound m40 - M4, second gantry after the M40. After that you are camera free till past M4 junction.
Variable speed limits - Dave N
And there was me thinking I was the only one that ever obeys the temporary limits!

I've never been able to work out why you see a sign that says 60, then you hit the back of queue. Surely the one just before the back of the Q should say 20, the one before that 40, and the one before that 60? But I guess if so few people obey them, then it doesn't matter what they say and when.
Variable speed limits - v8man
Although I dont condone it, you can safely travel through the variable limits in the M25 20mph above what they indicate without getting flashed. I have been to the Godstone control centre and the variable limits are controlled by a desktop PC! It gets information from sensors in and by the road. The algorythms it uses are updated by some university bods.
Variable speed limits - eMBe {P}
.... given that the road was clear and the signs
had just not been switched off, .... >>


V8man is right - the M25 variable limits are auto-controlled and are llegally binding. If they were showing too low a limit for the conditions, it may be that the system was malfunctioning or had broken down.

As for the old style varaible "dot-matrix" signs on other M-ways, these used to be advisory only and not "legally binding", but I am not sure if the law has been changed. These signs had to be manually set, unlike those on the M25.


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Variable speed limits - Altea Ego
Errrrrrr No they were NOT broken down. They can control them manually and do for accidents and roadworks. They are still legaly binding even when manually controlled. They have been on on that stretch late at night for months due to roadworks.
Variable speed limits - eMBe {P}
I (emBe) said >> .. IF they were showing too low a limit for the conditions, it MAY be that the system was malfunctioning or had broken down. .. >>

So, I made a conditional statement suggesting why something MAY or MAY NOT be true. Therefore I can stand by my statement 100%

Renault Family said: "Errrrrrr No they were NOT broken down. ..." So he knows something as FACT - it is not conditional, no ifs, buts or maybes. I wonder how he can be so 100% certain?




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Variable speed limits - Altea Ego
Watson My dear fellow, let us examine the facts.

The Section of the M25 southbound between M40 and M4 have been having the lights on late at night every weekday night for about 4 months.

There is road works going on, late at night, on the M25 a/c slip to M4.

Now given the above facts, what do you deduce about the lights?

Holmes
Variable speed limits - eMBe {P}
Holmes : thanks for the evidence. I have not driven past there at night, in the timeframe you mention, so I did not see that evidence. Does it mean Thommos' premise in starting this thread was wrong: "... there had clearly been an incident some time before but the road .... "
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Variable speed limits - Altea Ego
A red herring Watson, those road works guys are very messy.....
Variable speed limits - Colin M
Unfortunately last year I experience exactly what you did going south on the M25 joining from the M4. Traffic was moving briskly and I was in a stream at 75-80mph (proof how clear that section of the M25 was). The gantry up ahead was the first indicating a reduced limit of 60, I lifted off the pedal and started slowing with not much in front of me.

I know that section very well and the section up to the M3 can really slow up so I guessed it was on for traffic flow.

Ten days later I got a NIP and done for doing 74 in the 60 limit. Really unhappy about it but paid the £60 and got 3 points and an SP50.

Went out and bought an Origin Blue the following week which kindly tells me which of the gantries have active cameras and which don't (loads of cameras between J10 and J11 both ways).





Variable speed limits - Thommo
Commiserations for that Colin.

As you imply it can be hard to slow to the approriate speed when all around you are pressing on, and possibly dangerous too.
Variable speed limits - Altea Ego
The one thing that puzzles me about the variable speed limits on the M25 - is do they work when the signs are off? I have heard third hand reports about a mate of a mate who went through at 95 and got flashed.
The question is are they set to catch motorists who exceed the NSL when no limit is showing?
Variable speed limits - eMBe {P}
>> The question is are they set to catch motorists who exceed
the NSL when no limit is showing? >>


Holmes: Yes, definitely. Watson
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Variable speed limits - Altea Ego
Watson,

What facts do you know to support this conclusion?

Holmes
Variable speed limits - eMBe {P}
Holmes: numerous first-hand reports from people who sup in The Swan and Anglers on Manor Rd., WoT. ;-) ! Watson.

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Variable speed limits - Altea Ego
Probably the same mate of a mate then watson.

Holmes, ex WOT now Woodham. (much cheaper council tax watson!)
Variable speed limits - jeds
The M25 variable Speed Limits Regulations - known affectionately as the 'ROAD TRAFFIC SPECIAL ROADS M25 Motorway (Junctions 10 to 16) (Variable Speed Limits) Regulations 2001' specifically says: 'Nothing in these Regulations shall prejudice the operation of any other regulations made or having effect as if made under section 17 of the Road Traffic Regulation Act 1984.'

This means that when the 'Special' Reg's are not in operation
then the 'Normal' Regs apply. In other words @ 95 mph you'd be nicked.
 

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