Safe Speed Forums

Absolutely. I also rather think there will be even more sophisticated behaviours that will need to be considered.

The risk is that we end up with a billion pound white elephant that will perform worse than the system it replaces. And the fundamental reason for this is that we a very adaptable species that actively manages our own interactions with the environment - something that we're actually very good at. If we can avoid congestion we will do so, but to do so congestion has to be predictable. If we install 'advanced' management systems, congestion actually may well become LESS predictable.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

When my alarm wakes me up at 6:30 in the morning, the first thing I hear on the radio (for the last 10years) is that the motorway in the Leuven area is clogged. So don't tell me that people are not informed.

Exactly. Me too, you have a fair idea of where the busy bits are going to be before you get there, either by using past experience (regularly used routes) or by radio traffic bulletins.
Rush hour on many routes that I regularly use is often a finely balanced gamble, where you hope for a 1 mile stop-start jam instead of a 5 mile stop-start jam, and I believe that these "dosing" systems are intended to stave off the inevitable, and eek out the last bit of capacity as efficiently as possible using limited tools.
So I don't really expect dramatic results, maybe a slightly better flowing jam which starts a little later and finishes a little earlier.

Again, as I said, I'm not sure how successful they are, my impression is that they may help a little, and don't seem to make things worse, so the jury is out, but for the time being I'll give them the benefit of the doubt and assume that the traffic planners have done their homework and that the investment is, on balance, worth it.

Having said that, I generally object to the "control freakery" mentality, and I would not like to see these lights being implemented willy nilly at times and places when the traffic was not congested.

Confused? So am I!

The spanner in the works is the “transistor effect” that happens at m-way junctions. Traffic on the m-way (in the emitter/collector circuit) is interfered with to an inordinate degree by traffic coming from the junction (the base). Without active control, as you propose, the signal to cease base traffic from coming into the road is only given after the motorway already seized up!

The imperative has to be introduced before the motorway seizes up. That is because part of the concept of the m-way system is that the traffic on the road is isolated from local traffic systems, hence the use of limited access junctions which only interact with in controllable ways. This way of doing things ensures that the bandwidth of the road is maximized. Unfortunately, in city circumstances with many ramps, the isolation doesn't happen, and the system rapidly degenerates for both local and m-way traffic.

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I've checked out the Leuven area on multimap, and it looks like you have many tightly coupled motorway/local system connections there, which would lead to the congestion problems we have discussed.

One option is for planners to be harder on local politicians, and tell them that the road is coming through whether they like it or not, even though it won't be hooked up tightly to thier town! Sounds like a bad deal, but it might be the best tradeoff in some cases.

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I've been searching my experience and I can't recall flow breakdown associated directly with an on-slip - but I can find plenty associated with a tailed back off-slip.

This leaves me wondering about a secondary problem with ramp metering schemes. If we clog up the junction by gating (not basing * ) on slip traffic we risk tailing back the off-slip. And if we do that we get flow breakdown for sure.

* Maybe it's a FET?

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

Yes, some of it is coming back to me now - I last went over some of that stuff properly in 1979. In any case, it is the interaction between two circuits, sorry road-systems, that cause this. The mega-snarls-ups that happen on the M6 near Birmingham seem due to the dual nature of the road; as a high bandwidth carrier, and a local convenience route. In hindsight, this was poor planning, and a new road has been built to fix that screw up (although it has a costly toll).

Building new m-ways to solve the problem is becoming politically difficult. Faced with that, I am not surprised that "control-system like" solutions are being looked at. It goes without saying that they should be used only if they work well. Trials have to happen to gather that data.

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Yes to all of that. Especially the trials. But I'm dead worried about getting proper results from any trials for two reasons:

1) There's usually a vested interest or three in the trial.
2) There's a serious risk that trials will be too special, too small, too short (timescale) or too isolated to yield general (scalable) results.

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Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety

[quote="PeterC

When my alarm wakes me up at 6:30 in the morning, the first thing I hear on the radio (for the last 10years) is that the motorway in the Leuven area is clogged. So don't tell me that people are not informed.[/quote]

Great - now try driving up the M6 at 4-5 in the afternoon - there can be problems from J4 down or then again there may not be problems - have even been stuck in a jam having heard several radio reports on no problems.

But was not talking about radio reports - the motorways have CCTV /routemaster and signs - or are the signs there to display the saying of the week - seldom have i seen accurate congestion reports on them (apart from the usual -"M6 TOLLCLEAR)

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

The M6 TOLLCLEAR message is obvious anti-information, i.e. annoying noise that cannot help. The "road authorities" should be ashamed of this. Is there a road ombudsman to deal with that kind of thing?

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[quote="basingwerk
The M6 TOLLCLEAR message is obvious anti-information, i.e. annoying noise that cannot help. The "road authorities" should be ashamed of this. Is there a road ombudsman to deal with that kind if thing?[/quote]

There probably is , but the roads seem to have followed the rail pattern of "privatisation" from the signs i see on motorways - "this road maintained by xyz company on behalf of ........" -so would any action be forthcoming with so long a chain involved?And then (apart from the M6 toll thing) getting the various authorities to work together and use the information for the benefit of the road user ???? - the thread on another post on the accuracy of the information displayed says it all --
My favourite is the sign going north on the M6.the sign is just before J2 - have seen it say q after next junction - now does that mean J2 /J3/J4 --have actually gone off at J2 -to check on traffic flow toward J3 and failed to spot any problem.
Suspect that we won't see any movement in the direction of useful info untill Darling or one of his mates gets caught out.
That day i'll be wearing my hard hat to stop my head getting covered in pig droppings

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

That is correct. Leuven is a bottleneck for the traffic coming from the east.


I could not agree more. But unfortunately things do not work like that in reality.

You see, the plans were OK: it was never the intention of the planners to merge the 2 motorways coming from the east in Leuven. The original idea 30 years ago was to build an east west motorway only passing along Leuven going further to the west without passing along the Brussels or the Antwerp ringway (then already bottlenecks).

But when the construction of that new motorway was in the vicinity of Leuven, in the mid 80's, the plans were altered under local protest, and of course also because of lack of money. The ringway around Leuven originally only intended for switching between motorways and to handle a bit of local traffic was now used to connect the new motorway to the old one: it had to handle full motorway traffic plus local traffic. And that is what we pay the price for today.

Perhaps it could even be a JUGFET?

(JUnction Gate Field Effect Transistor for the uninitiated)

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"Are you sh**ing me?"
"John Spartan, you are fined one credit for a violation of the verbal morality statute."

Or an ECC82 with it's grid capacitors s/c ( twin triode valve for the young ones , directly heated cathode )

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lets bring sanity back to speed limits.
Drivers are like donkeys -they respond best to a carrot, not a stick .Road safety experts are like Asses - best kept covered up ,or sat on

Just to echo the point made , these have been in force for many years on the m6 in the midlands, and the pilot junctions in the Northwest are identified as suitable junctions to test. Also these lights can be easilt turned off if they are causing problems on the surrounding infrastructure.

Remember it is only a trial......