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)

Post by havaska_uk » Tue Nov 13, 2018 12:27

Not really a waste though is it? It was done as a test and data is now available for them to look at. That was the aim from the start.

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by Peter Freeman » Fri Apr 09, 2021 10:58

Was an official report on this experiment ever issued? If so, what were the conclusions (or, can you provide a link?).

Also, did the M62 eastbound east of the interchange ever get a 4th lane added?

In Melbourne, as partly reported elsewhere, 'connector metering' is now prevalent, covering almost half of all our M2M (motorway-to-motorway) interchanges. Implementation is imminent where the M31 Hume Freeway merges into both directions of the M80 Ring Road. (This is a minor component of an important current project widening the ring road at that location.) Metering is also included in the current Westgate Tunnel project, not only at each on-ramp but even on both connectors that combine to form one carriageway of a Q3M section. This comes very close to, effectively, metering a mainline.

It therefore appears that Melbourne's road designers have become fully convinced that widespread ramp and connector metering is beneficial.
Last edited by Peter Freeman on Fri Apr 09, 2021 22:27, edited 1 time in total.

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by jackal » Fri Apr 09, 2021 11:20

Peter Freeman wrote:
Fri Apr 09, 2021 10:58
Was an official report on this experiment ever issued? If so, what were the conclusions (or, can you provide a link?).

Also, did the M62 eastbound east of the interchange ever get a 4th lane added?
I never saw any report.

Yes, there is a fourth lane now. The J10-12 project was completed in January.

I think they also recently removed the ramp metering on the M62/M606 eastbound onslip when they removed the HOV lane. That one was 'sort of' freeflow M2M metering.

Surely there is a systemic lack of capacity (mainline lanes) if half Melbourne's motorway interchanges are ramp metered.

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by Bryn666 » Fri Apr 09, 2021 12:05

jackal wrote:
Fri Apr 09, 2021 11:20
Peter Freeman wrote:
Fri Apr 09, 2021 10:58
Was an official report on this experiment ever issued? If so, what were the conclusions (or, can you provide a link?).

Also, did the M62 eastbound east of the interchange ever get a 4th lane added?
I never saw any report.

Yes, there is a fourth lane now. The J10-12 project was completed in January.

I think they also recently removed the ramp metering on the M62/M606 eastbound onslip when they removed the HOV lane. That one was 'sort of' freeflow M2M metering.

Surely there is a systemic lack of capacity (mainline lanes) if half Melbourne's motorway interchanges are ramp metered.
I would argue the problems with M62 J10 are now entirely paint based and this points to the wider lack of understanding how driver psychology at interchanges work from HE.

Eastbound the M62 retains 3 lanes, but has a right hand lane drop to allow the M6 northbound slip road to create the 4th lane. The M6 southbound slip road creates a short lived 5th lane that ends after approximately 400 yards.

Westbound the M62 drops 2 lanes, but then widens back out to 3, meaning the M6 southbound merge has to give way, and the M6 northbound merge forms the 4th lane west to J9. This causes a massive amount of weaving.

I personally would have had the following lane allocations:

Eastbound: M6N | M6S | M62 | M62
Westbound: M6S | M6N | M62 | M62

That allows a double lane gain in both directions and prevents a lot of the weaving/lack of space to merge problems posed by the interchange. HE eventually figured out how to improve M62 J12 prior to the smart motorway by now having two direct M60 clockwise lanes and a tiger tail for anti-clockwise, instead of the former right hand exit.

It still baffles me why they mess about with things like traffic lights when ten mins with AutoCAD and some construction lines would solve most of their problems.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by Peter Freeman » Fri Apr 09, 2021 12:46

jackal wrote:
Fri Apr 09, 2021 11:20
Surely there is a systemic lack of capacity (mainline lanes) if half Melbourne's motorway interchanges are ramp metered.
I wouldn't put it like that, but we certainly do have a few places where further widening would be stupendously expensive and/or unacceptably damaging to amenity. And we do have a couple of as-yet-untreated notorious bottlenecks. However, the principle is that a DxM motorway with ramp metering has (approximately) the capacity of a D(x+1)M motorway without it. Right or wrong, that's the principle and the justification. A cost-effective capacity increase, like ALR.

On M2M, there is a 'purist' strain of thought within VicRoads that if a motorway section is to have coordinated ramp metering under the 'Hero' model, then all ramps and connectors on that section must be metered. I'm unconvinced yet on the M2M component, but, after initial skepticism, I have accepted that ramp metering generally is beneficial.

I suspect that the system would meet great resistance in the UK. I base this suspicion on my observation that UK drivers prefer to slowly crawl (even in your cars that have clutches) in an extended queue towards a 'throw-the-dice' give-way line, rather than endure a brief stop at a red signal. Am I too cynical ...?!

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by jackal » Mon Aug 02, 2021 11:34

Peter Freeman wrote:
Fri Apr 09, 2021 12:46
However, the principle is that a DxM motorway with ramp metering has (approximately) the capacity of a D(x+1)M motorway without it. Right or wrong, that's the principle and the justification. A cost-effective capacity increase, like ALR.
This is on its face a bizarre claim. For instance, would putting ramp metering on the (infrequent and quite lightly used) junctions on the D2M M74 between Uddington and Larkhall be equivalent to widening to D3M? Obviously not in any shape or form.

The claim assumes that merge capacity is the only significant capacity constraint, which only applies in a minority of cases. General mainline capacity and diverge capacity are also very significant factors and ramp metering does nothing for them.

Does ramp metering squeeze out a little extra capacity for a merge-limited mainline? Sure. But it inherently increases journey times on the signalized ramps compared to the freeflowing merges that lane gains and ghost islands can deliver, so must be considered a last resort where other measures cannot be provided for space or cost reasons.
Last edited by jackal on Mon Aug 02, 2021 14:12, edited 1 time in total.

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by Peter Freeman » Mon Aug 02, 2021 13:57

jackal wrote:
Mon Aug 02, 2021 11:34
Peter Freeman wrote:
Fri Apr 09, 2021 12:46
However, the principle is that a DxM motorway with ramp metering has (approximately) the capacity of a D(x+1)M motorway without it. Right or wrong, that's the principle and the justification. A cost-effective capacity increase, like ALR.
This is on its face a bizarre claim. For instance, would putting ramp metering on the (infrequent and quite lightly used) junctions on the D2M M74 between Uddington and Larkhall be equivalent to widening to D3M? Obviously not in any shape or form.
Obviously not, indeed. But that would not be a metering candidate in AU either. The system is used only on heavily-trafficked multi-lane urban motorways that are in width-constrained reservations, and have fairly closely-spaced interchanges. Generally speaking, we are fortunate in not having your heavily-trafficked rural motorways with infrequent interchanges.
The claim assumes that merge capacity is the only significant capacity constraint, which only applies in a minority of cases. General mainline capacity and diverge capacity are also very significant factors and ramp metering does nothing for them.
In most of Melbourne's implementations, mainline capacity improvement (widening, up to D6ALR, plus VSL, for example) has already occurred. Diverges are often 2-lane (though without ghost islands, except in one case), and sometimes use an early-start auxiliary lane and a lane-drop. The ramp-metering proponents observe that queueing, and backward-travelling congestion waves, are mainly caused by merges. The UK's use of tiger-tails and those giant lane-add diagrams at heavy merges surely shows that merges are the major problem?
Does ramp metering squeeze out a little extra capacity for a merge-limited mainline? Sure. But it inherently increases journey times on the signalized ramps compared to the freeflowing merges that lane gains and ghost islands can deliver, so must be considered a last resort where other measures cannot be provided for space or cost reasons.
Yes, I suppose it is a last resort. And yes, at most of the merges where it has been implemented, there is insufficient space for painting over valuable pavement area with ghost islands.

The theory behind ramp metering says that time spent queuing on the ramps is more than compensated by joining a free-flowing motorway at higher speed than would otherwise be the case. The theory further says that, once you've queued and joined, your journey for the rest of that motorway will be at-speed and congestion-free.

By the way, the period between greens ranges automatically (under 'Alinea' and 'Hero' algorithms) between 6 and 12 seconds, and on-ramps flare to 2, 3 or 4 lanes at the stop line. Maximum release-rate, when in operation, is therefore about 2400 pcu/hr. Queue lengths at peak times are typically 5-20 vehicles long. Most sites automatically activate only during morning and afternoon weekday peaks. A few have a bypass lane for trucks, motorbikes, taxis, buses and HOV's - but I have an impression that these are being phased out. A wander over Melbourne's M1, M2 and M80 using Google Earth shows most of the locations fairly clearly, though of course they're hardly ever caught in the act!

Melbourne is the exemplar implementation, but less comprehensive examples are in Sydney, Brisbane and Auckland NZ. Other AU cities also perhaps ...? There are erudite and mathematically rigorous papers delving into the theory and practise - search the web.

As I said, I still have some reservations myself, especially regarding M2M, but it does work. I realise that AU is a voice in the wilderness on this, which must stir doubts. Also, it's not cheap!

(edit to match jackal's, which I did already understand :smile: )
Last edited by Peter Freeman on Fri Aug 06, 2021 13:41, edited 3 times in total.

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by jackal » Mon Aug 02, 2021 14:46

While I accept the principle of ramp metering, M2M is particularly egregious as turning volumes can be as high as the mainline, and a forced stop imposes a bigger time delay and safety risk on an otherwise freeflow ramp than it does on a ramp from a city street.

If you end up with M2M you have basically not built your mainlines to match junction capacity. Probably it is no accident that the UK test site was Croft, easily the biggest interchange in the UK, but feeding a road that was 'only' D3M.

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by Bryn666 » Mon Aug 02, 2021 15:00

The reason for our ridiculously oversized exit and entry tapers where tiger tails are used is because the DMRB stubbornly refuses to allow the global standard of marking an optional lane - apparently this would be "confusing", even though experience of every tiger tail in the UK is people swoop across at the last minute. This was due to some, IMV, flawed research done by TRL in the late 90s.

The same research introduced the giant signs at diverges and merges, and no attention has been paid to them ever since.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by WHBM » Mon Aug 02, 2021 15:22

I've known ramp metering ever since the late 1970s when I first encountered it in Los Angeles, where it has become pretty standard now on urban sections. The freeway network there has not changed a lot, apart from the odd extra lane, in the last 40-50 years, such new sections as they have are outside the established core.

Unlike the Melbourne example, which apparently has fixed interval red/green, the LA timings are dynamic done by some radar on the nearside lane on the mainline. There's an LA myth that it actually spots individual gaps, but it's a bit more generalised than that. A lot of research was put in to the optimising algorithm, and it has always seemed to work well, then and now. The key value is to prevent being unable to join the mainline and having to come to a stand in the merge, which then saps capacity on both ramp and mainline as vehicles get going again from a standstill.

The "One Car Per Green" sign used to be larger, but everyone has now got used to it. Also disappeared was a flashing (neon ?) sign alongside which, if more than one went through on a green, used to flash on/off "VIOLATION" :) .

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by Peter Freeman » Mon Aug 02, 2021 15:45

WHBM wrote:
Mon Aug 02, 2021 15:22
I've known ramp metering ever since the late 1970s when I first encountered it in Los Angeles, ...
I've known it since 1980, when I first encountered it at Pennsylvania Avenue and Beltway, New York. It was quite primitive. I last observed USA metering in action in 2015 on one of Kansas City's freeways - still fairly primitive.
Unlike the Melbourne example, which apparently has fixed interval red/green, the LA timings are dynamic done by some radar on the nearside lane on the mainline.
Melbourne's intervals are not fixed. The whole integrated system, stretching uninterrupted for tens of kilometers right across the city, is very dynamic, sites being coordinated by the 'Hero' strategy. It uses buried and beam-interrupt road sensors, at least every 500m on each mainline lane, and at multiple locations on the ramps, rather than radar.
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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by Peter Freeman » Tue Sep 14, 2021 04:08

I've just been researching the Californian ramp metering system. Their system is extensive, but (generally) not sophisticated. Most documentation I've read is from 2017 - I assume it's largely still valid, since extensive upgrade is a multi-year task. Numbers below are from 2017.

The first site was implemented in 1971. The number of metered sites is 3000, 1000 of them in the Los Angeles area. Thirty are on freeway connectors, referred to in this thread and other places as 'M2M' (motorway-to-motorway). The majority of sites are activated during am and pm peak periods only, and are independent of each other. Experiments into, and pilots of, 'corridor-wide coordination' and 24x7 operation are underway. Standardisation of diverse firmware and software at the many sites, and major expansion to other sites, is planned.

Many characteristics of the CA implementations are broadly similar to our Australian ones: the turn-on triggering, release strategy (single vehicle per lane 'drip-feed'), ramp flaring, etc. Corridor-wide coordination in 2017 was clearly behind our 'Hero' system.

Caltrans are convinced that the technology works and that there is economic justification, citing their own data and a famous Minneapolis live experiment.

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by WHBM » Tue Sep 14, 2021 09:25

Key feature of California meters is that, on all the ones I can recall, on the ramp lane 1 is metered and lane 2 is a Diamond Carpool lane, bypassing the meter, as you can see in my example link above. Carpool in California means any car with more than one person in it. I have noticed when getting a lift from locals there that they are so wedded to driving on their own that, when I am with them, the still unconsciously queue up in the metered lane.

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Re: Motorway to motorway (M2M) metering pilot scheme M62 junction 10 (Croft Interchange)

Post by Peter Freeman » Tue Sep 14, 2021 10:44

WHBM wrote:
Tue Sep 14, 2021 09:25
Key feature of California meters is that, on all the ones I can recall, on the ramp lane 1 is metered and lane 2 is a Diamond Carpool lane, bypassing the meter, as you can see in my example link above. Carpool in California means any car with more than one person in it. I have noticed when getting a lift from locals there that they are so wedded to driving on their own that, when I am with them, the still unconsciously queue up in the metered lane.
This was referenced in the Caltrans documentation I've been finding too. IIRC, in some cases the concession lane provides a bypass, in others its release rate is faster. In Melbourne there are various concession treatments. Most are simply a bypass lane for trucks, buses and motorbikes, but some also include private cars with >1 occupant. There is no enforcement. I did read somewhere (I can't remember whether for USA or Australia) that recent thinking is to discontinue provision of bypass lanes. I don't know the reasoning.

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