Wales becomes Trumpton

[motorbiking]

Look its pretty simple.
If traffic was already mostly driving around 20mph. The speed limit wont make a difference, speeds wont change, casualty stats wont change. Assuming there was ever a link, there isn't particularly, its impact speed that kills.
If the speed limits are making a difference and vehicle speeds are slowing significantly, then the claim that journeys are only being impacted by 1 min, means that the avg journey is 1 mile.

In this universe it's not possible to slow speeds by 1/3rd and not have an increase of the same, for the given journey. There is of course a scenario where people go "feck it, its too painful to drive to work, I'll work from home again".

Meanwhile, once plod start enforcing it or Drakeford concludes its being ignored and wants it enforced, we will see many people driving at entirely sensible and safe speeds for the conditions being penalised severely.

Bloke in England does 36 on a restricted road = speed awareness
Bloke in Wales does 36 on a restricted road = 5 pts and a means tested fine.

 

[RandomGrinch]

If the speed limits are making a difference and vehicle speeds are slowing significantly, then the claim that journeys are only being impacted by 1 min, means that the avg journey is 1 mile.

In this universe it's not possible to slow speeds by 1/3rd and not have an increase of the same, for the given journey.

Firstly, only if the entire journey is within a restricted zone.

As stated earlier (and including the gross simplifications that have been used throughout these posts), for any length of journey, at a range of speeds, a minute of extra journey time may come about by a single mile of 20mph zone (instead of a 30), within the journey.

Secondly, the universe may disagree with you.
1 mile travelled at 30mph would take 2 minutes.
1 mile travelled at 20mph would take 3 minutes.
The journey length would have increased by 1/2.

There is of course a scenario where people go "feck it, its too painful to drive to work, I'll work from home again".

And to be fair, the WAG have been pretty blatant about that outcome from the start...

 

[Roy Bloom]

Look its pretty simple.
If traffic was already mostly driving around 20mph. The speed limit wont make a difference, speeds wont change, casualty stats wont change. Assuming there was ever a link, there isn't particularly, its impact speed that kills.
If the speed limits are making a difference and vehicle speeds are slowing significantly, then the claim that journeys are only being impacted by 1 min, means that the avg journey is 1 mile.

In this universe it's not possible to slow speeds by 1/3rd and not have an increase of the same, for the given journey. There is of course a scenario where people go "feck it, its too painful to drive to work, I'll work from home again".

Meanwhile, once plod start enforcing it or Drakeford concludes its being ignored and wants it enforced, we will see many people driving at entirely sensible and safe speeds for the conditions being penalised severely.

Bloke in England does 36 on a restricted road = speed awareness
Bloke in Wales does 36 on a restricted road = 5 pts and a means tested fine.

You're either ignoring the phantom traffic jams caused by concertina effect through ignorance, lack of thought, intenionally or through sheer determination.

It's very obvious on motorways when people speed between phantom traffic jams, thereby lengthening and perpetuating the phantom traffic jam.
If they all travelled at the often indicated speed the phantom jam would disappear, and/or wouldn't appear to start with. And traffic flow would be eased.

 

[motorbiking]

No argument from me that 20mph is going to take 50% longer, is the same as saying 30mph is 2/3rd quicker. The argument was journeys are only 1 min longer, which means they are only doing 1 mile or as said by RG 1 mile in a new 20 zone.

They are keen to show how many roads where “exempt” which means roads that had to be changed from restricted roads. But there is less information on the volume that changed.

£40m buys a lot of road signs and one news source claimed at least 1/3rd of the road network of wales had the limit changed.

The 1 mile of new 20 zone argument is hard to believe. I’d be interested in the methodology used to conclude “journey times”. I suspect thry have absolutely no way of knowing how long a journey is and are just looking at general traffic for a given section of road.

I appreciate this is from an official source.

Restricted roads are usually located in residential and built-up areas where there are lots of people. They often have street lights on them, placed no
more than 200 yards apart.

But it’s wrong.

Restricted roads must have street lights <183m apart otherwise they aren’t restricted roads. There is no requirement for them to be in built up areas where there are lots of people. Plenty of ring roads have street lights and limited pavement. They are restricted by the fact they have street lights. Nothing else. That’s how s81 etc is drafted

 

[Roy Bloom]

No argument from me that 20mph is going to take 50% longer, is the same as saying 30mph is 2/3rd quicker. The argument was journeys are only 1 min longer, which means they are only doing 1 mile or as said by RG 1 mile in a new 20 zone.

You are ignoring the effect of start-stop motoring through places with higher limits, where a steady lower speed eases traffic flow, is better for the air quality, reduces the stress on drivers and the reduced accidents or reduced injuries.

If drivers cannot plan for an incresae of journey times of 1 minute, they really shouldn't be driving.

 

[motorbiking]

You start out with a rational hypothesis - does 20mph mean traffic flows more smoothly than 30mph due to bunching.

It’s easy to think of “rush” hour traffic (though that has new meaning in Wales now) but you have to account for traffic every hour of the day. I suspect that even busy roads are free flowing 70% of the time.

But you go first with your arguments for a change.

 

[Roy Bloom]

You start out with a rational hypothesis - does 20mph mean traffic flows more smoothly than 30mph due to bunching.

It’s easy to think of “rush” hour traffic (though that has new meaning in Wales now) but you have to account for traffic every hour of the day. I suspect that even busy roads are free flowing 70% of the time.

But you go first with your arguments for a change.

It's a well-known phenomena, and I'm just presenting the argument for the concertina effect. The other issues (pollution, reduced accidents, etc) are well presented elsewhere.

The accordion effect in road traffic refers to the typical decelerations and accelerations of a vehicle when the vehicle in front decelerates and accelerates. These fluctuations in speed propagate backwards and typically get bigger and bigger further down the line, resulting in reduced throughput of road traffic.

Accordion effect - Wikipedia

en.wikipedia.org

Why a traffic flow suddenly turns into a traffic jam?

If there are enough cars on a highway, any minor disruptions to the flow of traffic can cause a self-reinforcing chain reaction: one car brakes slightly, and the ones behind it brake just a bit more to avoid hitting it, with the braking eventually amplifying until it produces a wave of stopped or slowed traffic.

Why do traffic jams sometimes form for no reason?

Vox is a general interest news site for the 21st century. Its mission: to help everyone understand our complicated world, so that we can all help shape it. In text, video and audio, our reporters explain politics, policy, world affairs, technology, culture, science, the climate crisis, money...

www.vox.com

 

[Brigadier]

It's a well-known phenomena, and I'm just presenting the argument for the concertina effect. The other issues (pollution, reduced accidents, etc) are well presented elsewhere.

Accordion effect - Wikipedia

en.wikipedia.org

Why do traffic jams sometimes form for no reason?

Vox is a general interest news site for the 21st century. Its mission: to help everyone understand our complicated world, so that we can all help shape it. In text, video and audio, our reporters explain politics, policy, world affairs, technology, culture, science, the climate crisis, money...

www.vox.com

In a 30 mph stretch of road though?
Really?

 

[Roy Bloom]

In a 30 mph stretch of road though?
Really?

Yes, I'm well aware of roads going through village type environments where a slower overall limit would ease the flow of traffic, both in Wales and elsewhere.
Think of many restricted roads going through local shopping centres in most UK cities, where the local shopping centre is along a road that does not have the benefit of a bypass.
Often in these situations,traffic speed is restricted by all sorts of measures, e.g. speed humps, traffic lights, road narrowing, etc.
These sorts of restrictions may not allow for more traffic. that was never the objective.
A sl;ower overall speed of all traffic, allowing easier and less resticted flow, has all the desirable effects.

 

[motorbiking]

It’s almost impossible to find any independent research that agrees. I’m not saying you are wrong just the vast majority of research is commissioned to prove a scheme was successful.

From a queuing theory point of view the space gained through being able to drive closer together (2 car lengths vs 3) is lost by the slower speed. For a vehicle of 6m avg, the capacity of the road at 30mph is double.

There can therefore only be a benefit from less bunching where bunching is the cause of slow traffic. You also have to consider the bunching caused by slower traffic speeds.

You cannot ignore the argument from the bus company that overall it’s having a significant impact. These vehicles are driving all day. Given who awards them their contracts I would say they are being diplomatic.

 

[Roy Bloom]

It’s almost impossible to find any independent research that agrees. I’m not saying you are wrong just the vast majority of research is commissioned to prove a scheme was successful.

From a queuing theory point of view the space gained through being able to drive closer together (2 car lengths vs 3) is lost by the slower speed. For a vehicle of 6m avg, the capacity of the road at 30mph is double.

There can therefore only be a benefit from less bunching where bunching is the cause of slow traffic. You also have to consider the bunching caused by slower traffic speeds.

You cannot ignore the argument from the bus company that overall it’s having a significant impact. These vehicles are driving all day. Given who awards them their contracts I would say they are being diplomatic.

The concertina effect causes stop - start slow - fast motoring, which is not economical motoring, is stressful, is not environmentally friendly, etc. The lower speed limit eases traffic flow which reduces the stop - start motoring.

The bus companies were complaining even before the new speed limits were introduced.
It presents them with an ideal opportunity to review services, and blame it on something else.

 

[Brigadier]

The lower speed limit eases traffic flow which reduces the stop - start motoring

On arterial-type roads, where traffic volume is the primary factor in "efficiency".
30mph roads have too many other confounding factors - crossings, parked vehicles, junctions and side roads, etc - for this to be a factor of any practical significance.

 

[carmanmemoranda]

No argument from me that 20mph is going to take 50% longer, is the same as saying 30mph is 2/3rd quicker. The argument was journeys are only 1 min longer, which means they are only doing 1 mile or as said by RG 1 mile in a new 20 zone.

They are keen to show how many roads where “exempt” which means roads that had to be changed from restricted roads. But there is less information on the volume that changed.

£40m buys a lot of road signs and one news source claimed at least 1/3rd of the road network of wales had the limit changed.

The 1 mile of new 20 zone argument is hard to believe. I’d be interested in the methodology used to conclude “journey times”. I suspect thry have absolutely no way of knowing how long a journey is and are just looking at general traffic for a given section of road.

I appreciate this is from an official source.


But it’s wrong.

Restricted roads must have street lights <183m apart otherwise they aren’t restricted roads. There is no requirement for them to be in built up areas where there are lots of people. Plenty of ring roads have street lights and limited pavement. They are restricted by the fact they have street lights. Nothing else. That’s how s81 etc is drafted

Every road in this country is restricted to a certain speed.

 

[motorbiking]

The term "Restricted Road" is a defined term. s81, s82

Road Traffic Regulation Act 1984

An Act to consolidate the Road Traffic Regulation Act 1967 and certain related enactments, with amendments to give effect to recommendations of the Law Commission and the Scottish Law Commission.

www.legislation.gov.uk

Every other road is not a restricted road, speed limits set as per s84 on.

 

[carmanmemoranda]

So 20, 40, 50, 60, nsl are not restricted