Default 20mph for Wales

[Bmblbzzz]

(In England, town councils are the same as parish councils in terms of their powers and duties. Not all parts of England are "parished" so some areas - especially in cities - don't have that layer of government. The equivalent bodies in Wales are called community councils.)

I've never lived in an area covered by either a town or parish council. Sometimes too rural, sometimes too urban!

[pwa]

Apparently Monmouthshire's review of 20mph roads has concluded that none will be returned to 30!
https://www.bbc.co.uk/news/articles/czepe606gn6o

[Bmblbzzz]

So they got it right first time – good! People often think it's odd to have A roads limited to 20mph, but it makes lots of sense precisely because those are the busiest; not just busiest with motorists but with pedestrians, cyclists, as well as shops and other businesses along the roadsides.

[roubaixtuesday]

Apparently Monmouthshire's review of 20mph roads has concluded that none will be returned to 30!
https://www.bbc.co.uk/news/articles/czepe606gn6o

Excellent

[pwa]

Thinking about the bits of Monmouthshire that I know, if I drove up there today I could get to Monmouth or Abergavenny almost entirely on fast roads not limited to 20mph, only having to drop to 20 for the last little bit as I enter the towns and seek out the car park. Slowing down for that last bit is no big deal. Most of the rest of the county is like that, with long journeys hardly impacted by relatively short 20 stretches through small towns and villages. So I can see why they stuck to their guns.

[Pete Owens]

A reminder to vote if you live in Wales.

[Ferrij]

It’s getting that the roads in the Vale of Glamorgan towns and villages are so bad that you can’t drive above 20mph unless you have a 4x4 . It seems the same uk wide too

[ratherbeintobago]

It’s getting that the roads in the Vale of Glamorgan towns and villages are so bad that you can’t drive above 20mph unless you have a 4x4 . It seems the same uk wide too

The irony being that a bigger, heavier vehicle like an SUV does more damage to the road surface in the first place?

[Bmblbzzz]

Yesterday morning I discovered a disadvantage of 20mph limits. When people obey the strictly, so they're driving at about 18-19mph, it's hard to resist drafting cars. This means I arrive at my destination – puff, pant – quite out of breath!

[mjr]

OK, I've seen an argument against 20mph in another forum that's new to me. It basically goes as follows:
· ICE cars are about 20% efficient with more of the energy used keeping the pistons moving and so on than actually propelling the vehicle along;
· it takes 50% longer to cover a distance at 20mph than 30mph;
· the 20%-efficient engine is running 50% longer and that outweighs the saving from a lower top speed.

I've challenged one aspect in two ways, as the difference is in legal top speeds not actual average speeds, and the average speed in 20mph zones is only 1mph slower than in 30mph due to less congestion but that finding was from a 2018 study of various towns and I didn't find any updated results from Wales. Are there any?

And the other way was to point out that each acceleration to 30 uses more energy than accelerating to 20, you don't have regenerative braking in a non-EV, and acceleration dominates in urban driving.

Can you think of other ways to debunk this bizarre argument? I've spared you all the pseudophysics about differentials, technical requirements and piston motion as a wave model through space-time because I don't think they matter. They seem like sciencey waffle to try to distract people and discourage arguments in favour of 20mph.

[Bmblbzzz]

I would certainly question the suggestion that more energy goes into keeping the pistons moving than propelling the vehicle. Apart from anything else, how is the vehicle propelled?

[mjr]

I would certainly question the suggestion that more energy goes into keeping the pistons moving than propelling the vehicle. Apart from anything else, how is the vehicle propelled?

They pasted the following from Wikipedia to support that claim:

Even when aided with turbochargers and stock efficiency aids, most engines retain an average efficiency of about 18–20%.[53]

The linked page http://courses.washington.edu/me341/oct22v2.htm has the "fuel-to-wheel" figures labelled "Eng" in the final table of the page, but no source is given, so I guess it's open to challenge if you have better.

[Mike Sales]

A driver truly concerned about efficiency and polluting less would be using an electric car, which does not have this problem of efficiency versus speed. A responsibly designed oil driven car would be most efficient at legal speeds. I see many cars left running whilst the driver nips into the shop. Besides being illegal, surely the bloody pistons are still moving.

[mattheus]

Can you think of other ways to debunk this bizarre argument?

By walking away? Watching some cute kitten videos??

They'll only come up with some other crazy pseudo-science to excuse some other car-brained bias!

[Carlton green]

OK, I've seen an argument against 20mph in another forum that's new to me. It basically goes as follows:
· ICE cars are about 20% efficient with more of the energy used keeping the pistons moving and so on than actually propelling the vehicle along;
· it takes 50% longer to cover a distance at 30mph than 20mph;
· the 20%-efficient engine is running 50% longer and that outweighs the saving from a lower top speed.

I've challenged one aspect in two ways, as the difference is in legal top speeds not actual average speeds, and the average speed in 20mph zones is only 1mph slower than in 30mph due to less congestion but that finding was from a 2018 study of various towns and I didn't find any updated results from Wales. Are there any?

And the other way was to point out that each acceleration to 30 uses more energy than accelerating to 20, you don't have regenerative braking in a non-EV, and acceleration dominates in urban driving.

Can you think of other ways to debunk this bizarre argument? I've spared you all the pseudophysics about differentials, technical requirements and piston motion as a wave model through space-time because I don't think they matter. They seem like sciencey waffle to try to distract people and discourage arguments in favour of 20mph.

Unless I’m mistaken it takes 50% longer to cover a distance at 20mph than at 30mph ( you might like to alter your post accordingly ).

There’s likely some truth in the assertion that it takes longer and uses more fuel to deliver goods in 20 mph zones than in 30 mph zones, how much more time and fuel is used isn’t clear to me and neither is its importance. The 20 mph zones aren’t about either fuel or time use they’re about safety and in that respect there’s been multiple real benefits to society.

Of course there might well be frustrations and pressures on delivery drivers who are prevented from driving faster than they might otherwise go; similarly there are times when I find local 20 mph limits frustrating but there are also times when I’d think it unwise to do as much as 30 mph (in a 30 mph zone). Speed limits aren’t a target speed, though a delivery drivers boss might think so, they’re a cap imposed by the State.

As an aside I welcome speed limits and find myself driving more slowly than I used to do, my journey times don’t seem noticeably longer but my stress levels are less and at the end of the journey I’m not needing recovery time.

TLDR. The delivery driver might be right, but the limit is there for public safety; we have no entitlement to drive on the roads and do so by license (a permission granted by the State). So obey the rules or forfeit your license, it’s quite simple really.