M25 Cameras and limits
Discussion
Number of factors involved here. The most fundamental is that even though they can change the speed limits on the matrices on the fly, the gantry gatsos are all preconfigured to fire at a given speed and cannot be changed remotely, so each gantry might have a camera set at 46, one at 58, another at 69 and one at 95.
When a speed limit is 70, only the camera set up for 95 is activated. When the limit goes down to 50, the gatsos which are setup for 95, 69 and 58 are activated.
So any given speed can only be monitored in one lane at a time and it's fair to assume that they do not arrange the cameras on each gantry the same way.
On top of this, consider the time and effort involved in changing all the films, and that only some cameras will have a film loaded at all at a given time.
The upshot is that the chances of getting nicked by an M25 gantry gatso are about the same as winning the lottery.
The exact same question was posted here a few months back and we didn't find anyone who'd had a ticket form an M25 gatso then...
When a speed limit is 70, only the camera set up for 95 is activated. When the limit goes down to 50, the gatsos which are setup for 95, 69 and 58 are activated.
So any given speed can only be monitored in one lane at a time and it's fair to assume that they do not arrange the cameras on each gantry the same way.
On top of this, consider the time and effort involved in changing all the films, and that only some cameras will have a film loaded at all at a given time.
The upshot is that the chances of getting nicked by an M25 gantry gatso are about the same as winning the lottery.
The exact same question was posted here a few months back and we didn't find anyone who'd had a ticket form an M25 gatso then...
I'd agree with your last comment - the variable limits do work. All thats needed is to raise the limit at off-peak times to 90...........
As for the cameras, I don't know - I've seen them flash a few times (not for me tho cos I NEVER speed
). I think they are more of a deterrent than an enforcement now. I seem to remember that when they were first introduced they were emptied on a daily basis, cos they wer taking happy snaps of so many people..
As for the cameras, I don't know - I've seen them flash a few times (not for me tho cos I NEVER speed
). I think they are more of a deterrent than an enforcement now. I seem to remember that when they were first introduced they were emptied on a daily basis, cos they wer taking happy snaps of so many people..Sorry CarZee, but you're not entirely right. It is quite true that the cameras have no remote control facility and that all changes have to be made on-site. Actually, changes can be made off-site and then read into the camera system via a PCMCIA flash card, but that's a bit hair-splitting. Someone still has to go out to the camera to make any changes.
However, you're quite wrong that the systems only enforce at one speed. The cameras are programmed with an enforcement speed for each of the valid speed limits that the matrix boards can display, which from memory is 'red X' (laned closed), 20, 30, 40, 50, 60 and NS (National Speed Limit). The operator sets the threshold speed for each of these on a per-limit basis, so that if the speed limit is 40 then the camera might enforce at 46mph (but it can be anything from 40-99mph, I seem to recall), whilst at 60 it might enforce at 68mph (but it could be anything from 60-99mph), and at NS the operator has a choice of setting a speed or disabling enforcement for NS.
However, enforcing NS is not part of the pilot scheme, so I would imagine that they have it turned off. But that's not to say they couldn't enable it if they wanted to - the system is quite capable of enforcing NS.
Hope that clears up any confusion.
Kind regards
Jon
However, you're quite wrong that the systems only enforce at one speed. The cameras are programmed with an enforcement speed for each of the valid speed limits that the matrix boards can display, which from memory is 'red X' (laned closed), 20, 30, 40, 50, 60 and NS (National Speed Limit). The operator sets the threshold speed for each of these on a per-limit basis, so that if the speed limit is 40 then the camera might enforce at 46mph (but it can be anything from 40-99mph, I seem to recall), whilst at 60 it might enforce at 68mph (but it could be anything from 60-99mph), and at NS the operator has a choice of setting a speed or disabling enforcement for NS.
However, enforcing NS is not part of the pilot scheme, so I would imagine that they have it turned off. But that's not to say they couldn't enable it if they wanted to - the system is quite capable of enforcing NS.
Hope that clears up any confusion.
Kind regards
Jon
John RB - you aren't John Robson are you, the (friendly) traffic policeman who used to post on the speed trap forum? I used to post there but things are a bit silly now, lots of rants - pistonheads is a bit more measured.
Cheers for info re M25 gantries. It is one motorway I never excessively speed on, so it must work, but it makes it a more stressful journey as I can't drive according to traffic flow, ie can't speed up to avoid blocking in etc. I once went thru a 40 temp limit at about 60 (road congestion had cleared) and was a tad worried, but never got a NIP.
Rgds
Domster
Cheers for info re M25 gantries. It is one motorway I never excessively speed on, so it must work, but it makes it a more stressful journey as I can't drive according to traffic flow, ie can't speed up to avoid blocking in etc. I once went thru a 40 temp limit at about 60 (road congestion had cleared) and was a tad worried, but never got a NIP.
Rgds
Domster
quote:Far worse than that - I wrote the control software for the camera system. This is basically the interface between the matrix board and the camera system and deals with all the variable speed limit stuff and telling the camera when it is allowed to enforce and at what speed.
ISTR reading somewhere that you were involved in the installation of this system
I was early on in my career then (it was 1993) and was young and idealistic and fell for all the talk of it speeding up the average speed of the M25 etc. Had I known how it would end up I might not have been so enthusiastic, but it was interesting work nonetheless.
I hope everyone can forgive me!
Unfortunately, that is not part of the system.
The original requirements called for inductive loops in the road to measure traffic density and adjust the variable speed accordingly. I think this requirement was farmed out to a separate project called "Midas" that was eventually shelved or something.
Regardless, it is not part of the system, which is a pity becuase, as you say, it might have been a damn sight more useful system if it had.
The original requirements called for inductive loops in the road to measure traffic density and adjust the variable speed accordingly. I think this requirement was farmed out to a separate project called "Midas" that was eventually shelved or something.
Regardless, it is not part of the system, which is a pity becuase, as you say, it might have been a damn sight more useful system if it had.
quote:
They would work a lot better if the speed limit they displayed bore some relation to the traffic density. I've sat in a queue while the signs say 60 and been told to stick to 40 on an almost empty motorway
That makes sense... in a bizarre sort of way. If you're stuck in a jam, and the guys at the front pull away doing sixty, then the jam will start to disperse.
On the other hand, if there's a jam five miles in front of you, if you're made to slow down to 40 on an empty motorway, the jam might have cleared before you get there, instead of piling up at 70 (of course) and adding to the back of the jam.
Still doesn't help the psychology of doing 40 on an emty motorway though
quote:
Far worse than that - I wrote the control software for the camera system. This is basically the interface between the matrix board and the camera system and deals with all the variable speed limit stuff and telling the camera when it is allowed to enforce and at what speed.
I was early on in my career then (it was 1993) and was young and idealistic and fell for all the talk of it speeding up the average speed of the M25 etc. Had I known how it would end up I might not have been so enthusiastic, but it was interesting work nonetheless.
I hope everyone can forgive me!
No you can only achieve true forgiveness by assisting us with enlightnment. In other words have you got any good tips for wrecking the system?
I've just been sent a request from the MET as to whether I was riding my bike near the collingdale junction on the M25 just before junc. 14. It was a 50mph variable limit on the gantries and they are considering prosecution as I was exceeding this. The letter does not contain information of how fast I was going though. just to let you know that the gantries do work. Not sure whether I was tanking it through on my bike or not but I have before and never been caught??!!?? Anyone else been caught around here??
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