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MikeB Frequent Visitor
Joined: 20/08/2002 11:51:57 Posts: 3859 Location: Essex, UK
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Posted: Fri Jul 18, 2014 11:54 am Post subject: Managed Motorways catch thousands of speeders |
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Managed Motorways with variable speed limits have been in action in the UK for some time now. Starting with the M25 around the M4 intersection the overhead gantries sprung up sporting speed cameras. The variable speed limits were designed to slow traffic and help control the traffic flow. Initially the speed cameras were only active when there was a speed limit in force.
Now as the managed motorways have evolved into Smart Motorways we are seeing new styles of camera being installed, some sections are controlled by the average speed cameras, others by the newer HADECS, and the traditional gantry cameras still remain. Not only are there more and differing types of camera but some are also active at all times and not just when there is a speed restriction in place.
Drivers in the Bristol area have been finding this out the hard way, according to the BBC, where some 1,500 tickets have been issued in the first two weeks of operation. Although the works had been finished in January the cameras were only activated recently. Most of the offences were committed when there was a variable speed restriction in place. When there was no restrictions 70 drivers were ticketed in excess of 70 MPH and 3 over 100 MPH. In essence 1,430 drivers have no excuse as the speed restriction was clearly marked on every gantry.
This may be due in part to drivers disbelieving the signage, seeing a speed restriction when the road ahead was obviously clear. Often when driving on the managed motorways there are speed restrictions for no apparent reason, and this can lull drivers into a false sense of lack of danger and disbelief of the signage. This is especially the case when the signs say there is congestion ahead and reduce the speed limit and there is no indication of heavy traffic let alone congestion.
This could be caused by the Smart Motorway systems not being tuned correctly. The Smart Motorways use sensors to determine traffic flow and automatically set the speed restrictions. If the systems are not set correctly they can reduce the speed limit when there is no need. Drivers will note this and start to disregard the restrictions which could be the cause of the high number of tickets issued in the Bristol area.
The takeaway from all this is that even if the road systems are erroneously setting speed restrictions drivers still need to obey the signs or they will get a fine through the post. Also the cameras may be active at the permitted speed limit even when there is no sign illuminated. _________________ Mike Barrett |
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pdfbt40 Occasional Visitor
Joined: Jan 23, 2008 Posts: 56
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Posted: Fri Jul 18, 2014 2:53 pm Post subject: |
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Why do I get the feeling Managed/Smart motorways computer systems aren't optimised for quick traffic response but for a large hysteresis (time/distance delay). Accidentally that would lead to bias of inappropriate speed limits on clearing roads - Bang, revenue generator ! |
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DennisN Tired Old Man
Joined: Feb 27, 2006 Posts: 14901 Location: Keynsham
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Posted: Fri Jul 18, 2014 6:34 pm Post subject: |
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pdfbt40 wrote: | Why do I get the feeling Managed/Smart motorways computer systems aren't optimised for quick traffic response but for a large hysteresis (time/distance delay). Accidentally that would lead to bias of inappropriate speed limits on clearing roads - Bang, revenue generator ! |
Wot?? _________________ Dennis
If it tastes good - it's fattening.
Two of them are obesiting!! |
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Guivre46 Frequent Visitor
Joined: Apr 14, 2010 Posts: 1262 Location: West London
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Posted: Fri Jul 18, 2014 8:11 pm Post subject: |
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I think it means that the system responds quickly to traffic build up, but takes its time responding to its easing??
Or have you got your tongue in your cheek again? _________________ Mike R [aka Wyvern46]
Go 530T - unsupported
Go550 Live [not renewed]
Kia In-dash Tomtom |
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pdfbt40 Occasional Visitor
Joined: Jan 23, 2008 Posts: 56
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Posted: Fri Jul 18, 2014 10:17 pm Post subject: |
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Sorry, must reduce the technical jargon a bit. I'll try to remember.
Yes that's exactly what I mean, and explains why individuals complain of jams with no speedlimits and clear roads with 40mp.
In fact, the systems are more than able to be very sophisticated in anticipating increasing volume/queues and their clearing, much more than they are set to do.
Maybe that's like a decade or so back when somebody challenged a prosecution for speeding on M25. In court, he claimed there were no signs illuminated. The authority, at first made excuses why records were not available, eventually they produced a scruffy log book of dates but no entries, as previously claimed, of flow data, signs on/off, etc.
To really screw things up still needs people. |
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Kremmen Pocket GPS Verifier
Joined: Mar 03, 2006 Posts: 7125 Location: Reading
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Posted: Sat Jul 19, 2014 5:56 am Post subject: |
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I can see the logic. I use the M25 western section regularly and everyone ignores the variable limit because it has been known for years that the cameras are not active.
As a result cars are steaming up to the back of a jam and adding to/causing a jam further along.
Back in 2004/5 when they widened this section they put in place a series of 40mph working cameras to protect the workforce. The result was that from the M3 to the M4 all cars did 40mph.
That is the only time I can remember where this section flowed smoothly every day of the week. If drivers followed the 40mph signs now then I believe the jam that starts (clockwise) where the M4 joins the M25 (J15) and (anticlockwise) where the M3 joins the M25(J12) then it would work better. _________________ DashCam:
Viofo A119 V3 |
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pdfbt40 Occasional Visitor
Joined: Jan 23, 2008 Posts: 56
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Posted: Sat Jul 19, 2014 6:49 am Post subject: |
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The original core of traffic flow modelling was taken from Chemical Engineering Fluid Flow programmes.
Vehicles are taken to be a compressible fluid, so density can increase as velocity falls (not retaining safe distance). Very quickly they were able to create 'phantom jams' with duration and size.
Unfortunately drivers don't know to obey the rules of the computer models, and whilst it can react to a full stop of an accident, it can't predict it. |
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DennisN Tired Old Man
Joined: Feb 27, 2006 Posts: 14901 Location: Keynsham
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Posted: Sat Jul 19, 2014 8:03 am Post subject: |
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pdfbt40 wrote: | To really screw things up still needs people. |
Thank goodness for that. I was beginning to feel useless. _________________ Dennis
If it tastes good - it's fattening.
Two of them are obesiting!! |
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DennisN Tired Old Man
Joined: Feb 27, 2006 Posts: 14901 Location: Keynsham
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Posted: Sat Jul 19, 2014 8:05 am Post subject: |
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pdfbt40 wrote: | The original core of traffic flow modelling was taken from Chemical Engineering Fluid Flow programmes.
Vehicles are taken to be a compressible fluid, so density can increase as velocity falls (not retaining safe distance). Very quickly they were able to create 'phantom jams' with duration and size.
Unfortunately drivers don't know to obey the rules of the computer models, and whilst it can react to a full stop of an accident, it can't predict it. |
Wot?? Now I'm back to useless again!
My dear old granny used to say you can't beat a good Chemical Engineering Fluid Flow analysis. I wish I'd paid attention. _________________ Dennis
If it tastes good - it's fattening.
Two of them are obesiting!! |
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pdfbt40 Occasional Visitor
Joined: Jan 23, 2008 Posts: 56
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Posted: Sat Jul 19, 2014 11:17 am Post subject: |
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Oops. Sorry DennisN.
What I was trying to express, was that the Highway engineers didn't have to invent massive new knowledge to model the flow of traffic. In terms of the computer/mathematics, 'water hammer' in a pipe is the same sort of thing as a 'phantom jam' on a motorway. |
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DennisN Tired Old Man
Joined: Feb 27, 2006 Posts: 14901 Location: Keynsham
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Posted: Sat Jul 19, 2014 11:25 am Post subject: |
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You can do the same thing using marbles in a bucket. But I've forgotten how. _________________ Dennis
If it tastes good - it's fattening.
Two of them are obesiting!! |
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253 Lifetime Member
Joined: Mar 05, 2007 Posts: 1058 Location: The green bit between the M40, M4 and M25.
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Posted: Mon Jul 21, 2014 9:07 am Post subject: |
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DennisN wrote: | pdfbt40 wrote: | To really screw things up still needs people. |
Thank goodness for that. I was beginning to feel useless. |
, nice one. _________________ Triumph Tbird 1700. And now a Bonnie T100. |
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M8TJT The Other Tired Old Man
Joined: Apr 04, 2006 Posts: 10118 Location: Bexhill, South Sussex, UK
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Posted: Mon Jul 21, 2014 9:22 am Post subject: |
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DennisN wrote: | You can do the same thing using marbles in a bucket. But I've forgotten how. | What? Water hammer? I always thought the you needed water, a pipe and some sort of tap. |
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DennisN Tired Old Man
Joined: Feb 27, 2006 Posts: 14901 Location: Keynsham
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Posted: Mon Jul 21, 2014 11:17 am Post subject: |
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Nah! Just a bucket and some marbles. If I remember how, I'll let you know. _________________ Dennis
If it tastes good - it's fattening.
Two of them are obesiting!! |
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pdfbt40 Occasional Visitor
Joined: Jan 23, 2008 Posts: 56
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Posted: Mon Jul 21, 2014 2:38 pm Post subject: |
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M8TJT wrote: | DennisN wrote: | You can do the same thing using marbles in a bucket. But I've forgotten how. | What? Water hammer? I always thought the you needed water, a pipe and some sort of tap. |
OK, I give up. Obviously education is not part of this forum. |
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