Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
They are everywhere around the NW though.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
Yes, this claim is counter-intuitive, but proponents (of standard drip-feed ramp metering) offer some very complex modelling, plus experimental results, that supposedly explain it. The relevant documentation can be found online, but briefly:ScottB5411 wrote: ... I fail to see how making already stationary or nearly stationary traffic stay stationary for longer will make things better. ...
Too high a rate of intrusion at a merge point, when the mainline is already at high flow, causes 'breakdown'. At this point the capacity, speed and flow-rate all suddenly drop. Curves of these variables plotted against time now 'fold back' on themselves, meaning that the section of road cannot regain its carrying capacity until the flow rate (or, technically, the lane occupancy) is reduced further. That will not occur while the intrusion persists, hence the need to meter the intrusion to either prevent the breakdown from initially occurring, or, worst case, to allow it to reset.
Sounds crazy? I tend to agree: I haven't personally seen the practise match this theory. At Croft I'm certain that a lane-gain to the next junction (cheaply by ALR) would be a far better plan.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
None of which are on a 70mph link road from one motorway to another Bryn. You are still in essence on the mainline but just moving from motorway to motorway. There isn't a roundabout or other obstacle you need to navigate to get from one to the other like the M18 to A1M, that's the difference. Of course, it won't be 70 for long, I'm sure. Saddens me to see the nanny state taking over the road network as everything is dumbed down for inadequately trained drivers who need to be told how to do everything at all times.Bryn666 wrote:I think M6 J5 still has a ramp meter.
They are everywhere around the NW though.
Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
Let's take the other example where it is possible to be doing well in excess of 70 around a relatively blind bend into a ramp meter - Roscoe's Spur. That's still NSL, and has the exact same 'problem' as Croft.
When the ramp meters are active, the M62 and/or M6 are going to be moving slowly anyway due to the fact the ramp meters are only switched on when it is congested.
Whilst I don't see the point in this scheme, I'm at a loss why all the bile and fiction over it.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
A lane gain with a tiger tail hasn't given the required results, so now it's being tacked by flow metering.Bryn666 wrote:Whilst I don't see the point in this scheme...
I agree that the underlying problem is the Eccles-Wardley stretch of the M60.
Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
That's what I mean. Arguably if any motorway junctions needed ramp meters it was Eccles. As I said before, most of the NW motorway network problems can be traced back to M60 J12. Sort that and much of the region's congestion will go away.nowster wrote:A lane gain with a tiger tail hasn't given the required results, so now it's being tacked by flow metering.Bryn666 wrote:Whilst I don't see the point in this scheme...
I agree that the underlying problem is the Eccles-Wardley stretch of the M60.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
First, remember that these ramp meters are all coordinated (by a computerised system called 'Hero'). The main bottleneck on the M1 heading SE out of Melbourne is at Exit N (I can't remember the real number) where the M420 branches off and the M1 loses 2 lanes. Traffic severely slows and queues for many junctions upstream, whose on-ramps are therefore metered. The first to switch on would normally be at Junction N-1 (N minus one). Next would be N-2, by its own sensors or by recruitment from N-1 under Hero's command. Junction N-3 is where the un-metered M3 freeflow connector merges in, so the next to switch on is N-4. Then N-5, etcetera. There are two problems with this -
A. Junction N-2 recruiting assistance from N-4 doesn't help much when N-3, an un-metered freeflow connector from a crossing motorway, can still supply copious traffic.
B. Many of the vehicles entering at far-upstream on-ramps N-4, N-5, N-6, etc, are not actually aiming to continue SE on the M1: they intend to exit before the congested area (most going onto the M3). They are therefore not part of the problem, but they are being (needlessly) inconvenienced.
My solution to problem A is that upstream recruitment by Hero should not extend past a freeflow entry. My solution to problem B is that upstream recruitment by Hero should extend over only a limited range of junctions (say 4). VicRoads' published solution is that, on a route with metering, every single entry must be metered - no exceptions. Hence the development that is about to occur here. It might work ....?!
An irony is that other aspects of the current major smartification and widening project will remove the actual lane-drop downstream that is the current cause of congestion . And M3's entry onto M1 outbound will be a lane-gain (4+1=5) .
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
It's been knarled up in rush hour since the dawn of time, what's the sudden need to make it move anyway? By the time they've finished doing all the tinkering, I wonder how much money could have gone towards sorting out Eccles?nowster wrote:A lane gain with a tiger tail hasn't given the required results, so now it's being tacked by flow metering.Bryn666 wrote:Whilst I don't see the point in this scheme...
I agree that the underlying problem is the Eccles-Wardley stretch of the M60.
Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
Just because something has been broken for a long time doesn't mean it shouldn't be fixed.ScottB5411 wrote: It's been knarled up in rush hour since the dawn of time, what's the sudden need to make it move anyway? By the time they've finished doing all the tinkering, I wonder how much money could have gone towards sorting out Eccles?
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
I agree, but the cause as stated elsewhere isn't being fixedJeni wrote:Just because something has been broken for a long time doesn't mean it shouldn't be fixed.ScottB5411 wrote: It's been knarled up in rush hour since the dawn of time, what's the sudden need to make it move anyway? By the time they've finished doing all the tinkering, I wonder how much money could have gone towards sorting out Eccles?
Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
There is also ramp metering at the end of the Bryn Spur (M6 J25), which again is a road you can do in excess of 70 and then hit a ramp meter. It too is NSL.Jeni wrote:M60 J2 has ramp metering at the end of a 900m long slip road.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
The ones in the NW are just platoons of 3 or 4 vehicles from both lanes, we don't have any sites with one vehicle per lane per green as far as I am aware.Peter Freeman wrote:I didn't realise there were so many ramp-metering sites in the UK. Can someone make a list? Which ones are still active? Do they work? Are they drip-feed - eg. one vehicle per lane per green? (I understand some early ones released platoons).
The approaches to ramp meters are preceded by this sign: https://goo.gl/maps/iaoRMtKQftH2, followed by: https://goo.gl/maps/Nuevn9Usemv, then the signals themselves have a bespoke backing board: https://goo.gl/maps/quKbhJXijXL2
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
There's also a set at M5 J1 northbound entry slip.Chris Bertram wrote:The signal heads on blue diamonds survived on the NB on-slip at M6 J10 until it was reconfigured as a smart motorway. Ironically, I never saw those signals in use, while the SB set, in the now-customary yellow oval, were often in operation. You are correct that the signals on the M6 are all now gone, while at least one set survives on M42 at my nearest junction, J3 for A435, where they control the EB on-slip on a part time basis.
The northbound entry at M6 J10 has simply had the signal heads removed - the support posts are still there.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
Around a corner too. Not an ideal place where people are accelerating, only to find the back of a queue.Jeni wrote:M60 J2 has ramp metering at the end of a 900m long slip road.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
Try The Roaders' Digest: The SABRE WIki.Peter Freeman wrote:I didn't realise there were so many ramp-metering sites in the UK. Can someone make a list? Which ones are still active? Do they work? Are they drip-feed - eg. one vehicle per lane per green? (I understand some early ones released platoons).
Ramp Metering
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From the SABRE Wiki: Ramp Metering :
Ramp Metering are part-time traffic lights installed on slip roads in order to control the flow of traffic joining a major road, most usually a motorway. These traffic lights simply hold traffic on the slip road in an attempt to mitigate the congestion effects of traffic joining the major road by allowing traffic to flow along the major road and help minimise flow collision.
The first installation of ramp metering in the United Kingdom was installed in May 1986 on the M6 at
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)
It's not at all counter-intuitive.Peter Freeman wrote:Yes, this claim is counter-intuitive, but proponents (of standard drip-feed ramp metering) offer some very complex modelling, plus experimental results, that supposedly explain it. The relevant documentation can be found online, but briefly:
Too high a rate of intrusion at a merge point, when the mainline is already at high flow, causes 'breakdown'. At this point the capacity, speed and flow-rate all suddenly drop. Curves of these variables plotted against time now 'fold back' on themselves, meaning that the section of road cannot regain its carrying capacity until the flow rate (or, technically, the lane occupancy) is reduced further. That will not occur while the intrusion persists, hence the need to meter the intrusion to either prevent the breakdown from initially occurring, or, worst case, to allow it to reset.
Sounds crazy? I tend to agree: I haven't personally seen the practise match this theory. At Croft I'm certain that a lane-gain to the next junction (cheaply by ALR) would be a far better plan.
Traffic in many ways behaves like a fluid. When the flow breaks down, turbulence is introduced and it's only when the turbulence is cleared can the fluid flow freely once more - which isn't at the same flow rates as it is created. Try a simple experiment with a tap to see what I mean - if you turn the tap on to the point where the flow breaks down and you get turbulence, you have to turn it down further to restore smooth flow.
You see this in many other applications - networking for example, where you get an equivalent of turbulence (packet collision), and it's only when the collisions are removed can flow capacity be restored to its maximum smooth rate.
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