Speed limit to be lowered to 20mph in Wales

[CliffEdge]

Modern cars are ridiculous. They should be limited to 55mph max. There is no rational argument against that. Of course there are lots of yobbos (who enjoy tearing around imagining they're fantastically skilled drivers) who would object.

[DrFfybes]

Modern cars are ridiculous. They should be limited to 55mph max. There is no rational argument against that. Of course there are lots of yobbos (who enjoy tearing around imagining they're fantastically skilled drivers) who would object.

Rubbish. They should be limited to 52, much safer but minimal impact on journey times.

Now there's no rational arguement against that.

[dionaeamuscipula]

Modern cars are ridiculous. They should be limited to 55mph max. There is no rational argument against that. Of course there are lots of yobbos (who enjoy tearing around imagining they're fantastically skilled drivers) who would object.

Rubbish. They should be limited to 52, much safer but minimal impact on journey times.

Now there's no rational arguement against that.

Yes, there is, which is why speed limits in MPH and KPH countries are in general in round numbers.

And I doubt the impact speed difference under braking between a 55 vs 52 starting speed is going to significantly affect the outcome.

DM

[quelquod]

Rubbish. They should be limited to 52, much safer but minimal impact on journey times.

Now there's no rational arguement against that.

Yes, there is, which is why speed limits in MPH and KPH countries are in general in round numbers.

And I doubt the impact speed difference under braking between a 55 vs 52 starting speed is going to significantly affect the outcome.

DM

Around 10% if you don’t have time to hit the brakes? Might make all the difference. “Speed doesn’t kill” as they say but by a huge margin it’s the main contributor to the outcome of an accident.

[DrFfybes]

Around 10% if you don’t have time to hit the brakes? Might make all the difference. “Speed doesn’t kill” as they say but by a huge margin it’s the main contributor to the outcome of an accident.

Technically it is how quickly you change momentum that hurts, not how fast you are going.

Hitting the side of a car at 25 mph as it emerges from a car park has hurt a lot more than sliding 100 yards or more towards a waiting marshall, although I do remember consciously rolling over once as my side was getting quite warm.

Paul

[stevensfo]

Yes, there is, which is why speed limits in MPH and KPH countries are in general in round numbers.

And I doubt the impact speed difference under braking between a 55 vs 52 starting speed is going to significantly affect the outcome.

DM

Around 10% if you don’t have time to hit the brakes? Might make all the difference. “Speed doesn’t kill” as they say but by a huge margin it’s the main contributor to the outcome of an accident.

I remember a long time ago, kinetic energy impacting the target is mass x velocity squared.

So a car weighing 2 tons will impact with 2x the force of a 1 ton car.

But a car going 40mph will impact with 4x the force of a car at 20mph.

That's why the speed is so important.

Steve

PS I learned all this years ago when I was into air guns and became interested in ballistics. Yep, as a scientist, I was more into the theory than hitting the target!

[88V8]

Around 10% if you don’t have time to hit the brakes? Might make all the difference. “Speed doesn’t kill” as they say but by a huge margin it’s the main contributor to the outcome of an accident.

I remember a long time ago, kinetic energy impacting the target is mass x velocity squared.
So a car weighing 2 tons will impact with 2x the force of a 1 ton car.

And cars, like many of their owners, have become grotesquely heavy.
Mini from 1960 = 1280 lb
So-called Mini of 2023 = 2890 lb, and that's not even the electric version !

Cars should be speedlimited by weight.

V8

[quelquod]

I remember a long time ago, kinetic energy impacting the target is mass x velocity squared.

So a car weighing 2 tons will impact with 2x the force of a 1 ton car.

But a car going 40mph will impact with 4x the force of a car at 20mph.

That's why the speed is so important.

Steve

PS I learned all this years ago when I was into air guns and became interested in ballistics. Yep, as a scientist, I was more into the theory than hitting the target!

The years aren’t kind to the memory.
Kinetic Energy is 0.5 x mass x velocity squared (for non-relativistic velocities).
Sorry, couldn’t resist.

[stevensfo]

I remember a long time ago, kinetic energy impacting the target is mass x velocity squared.

So a car weighing 2 tons will impact with 2x the force of a 1 ton car.

But a car going 40mph will impact with 4x the force of a car at 20mph.

That's why the speed is so important.

Steve

PS I learned all this years ago when I was into air guns and became interested in ballistics. Yep, as a scientist, I was more into the theory than hitting the target!

The years aren’t kind to the memory.
Kinetic Energy is 0.5 x mass x velocity squared (for non-relativistic velocities).
Sorry, couldn’t resist.

Okay, I forgot the 0.5x bit, but the illustration of effect of velocity vs mass is still valid.

Besides, who cares if it's 1.0x or 0.5x?

Liz Truss was quite impressed with my accountancy skills!


Steve

[dealtn]

Cars should be speedlimited by weight.

V8

And how would you do that in a practical sense? How would you envisage lighter cars not being held up heavier ones.

They shouldn't be speed limited by weight.

[CliffEdge]

I remember a long time ago, kinetic energy impacting the target is mass x velocity squared.
So a car weighing 2 tons will impact with 2x the force of a 1 ton car.

And cars, like many of their owners, have become grotesquely heavy.
Mini from 1960 = 1280 lb
So-called Mini of 2023 = 2890 lb, and that's not even the electric version !

Cars should be speedlimited by weight.

V8

Modern cars are ridiculous by design. Amazing that no-one seems to bother. Limit the power of vacuum cleaners, yes, but cars, no-one cares what an abomination they've become.
Crazy.

[stevensfo]

And cars, like many of their owners, have become grotesquely heavy.
Mini from 1960 = 1280 lb
So-called Mini of 2023 = 2890 lb, and that's not even the electric version !

Cars should be speedlimited by weight.

V8

Modern cars are ridiculous by design. Amazing that no-one seems to bother. Limit the power of vacuum cleaners, yes, but cars, no-one cares what an abomination they've become.
Crazy.

I have a friend who's just retired and is going to buy a new car. He was showing me the models he's considering and I realised that a major factor for him was the 0-60 in xx seconds data!

I thought he may be joking and reminded him that it's not the 80s any more and we're not Starsky and Hutch etc.

Besides, where the hell these days can we safely do 0-60 in 1 nanosecond and why would you want to anyway?

Completely bonkers!

Steve

[bungeejumper]

I have a friend who's just retired and is going to buy a new car. He was showing me the models he's considering and I realised that a major factor for him was the 0-60 in xx seconds data!

I thought he may be joking and reminded him that it's not the 80s any more and we're not Starsky and Hutch etc.

Besides, where the hell these days can we safely do 0-60 in 1 nanosecond and why would you want to anyway?

Completely bonkers!

Up to a point, certainly. But there's a threshold where it can become dangerous to be too slow on the uptake, and I can think of a fair few situations where it wouldn't feel good to have less than 62 in ten seconds under your welly. My Toyota does it in nine.

My personal bete noire is the northbound Newbury bypass, where the inlet roads are too short to give you much protection if a 44 tonner should come round the bend behind you in the inside lane. You need to be outta there before you become a scrap metal sandwich. Others will have their own un-favourites.

None of which has much to do with the 20 mph limit in towns, though.

BJ

[stevensfo]

I have a friend who's just retired and is going to buy a new car. He was showing me the models he's considering and I realised that a major factor for him was the 0-60 in xx seconds data!

I thought he may be joking and reminded him that it's not the 80s any more and we're not Starsky and Hutch etc.

Besides, where the hell these days can we safely do 0-60 in 1 nanosecond and why would you want to anyway?

Completely bonkers!

Up to a point, certainly. But there's a threshold where it can become dangerous to be too slow on the uptake, and I can think of a fair few situations where it wouldn't feel good to have less than 62 in ten seconds under your welly. My Toyota does it in nine.

My personal bete noire is the northbound Newbury bypass, where the inlet roads are too short to give you much protection if a 44 tonner should come round the bend behind you in the inside lane. You need to be outta there before you become a scrap metal sandwich. Others will have their own un-favourites.

None of which has much to do with the 20 mph limit in towns, though.

BJ

Yes, I agree that a good acceleration can be a safety factor in certain situations. When overtaking, my Volvo packs a punch and I have time to safely overtake and change lanes very fast.

I think that most cars are capable of sufficient acceleration from 0-60. If not then they have to wait a little longer before getting on the road.

Besides, even if you get on the motorway and can't get to 60 in one second, the guy behind you has something called a brake.

Then you should charge him a medical fee for curing his constipation!


Steve

[CliffEdge]

Good points. 0 to 55 should be regulated but I imagine making 8.2 seconds quickest would be OK.

[88V8]

Cars should be speedlimited by weight.

And how would you do that in a practical sense? How would you envisage lighter cars not being held up heavier ones.
They shouldn't be speed limited by weight.

Good point. OK, taxed by weight.

Or you could give light cars speed-limit exemptions on a sliding scale.

Just as well I'm not in charge....

V8

[quelquod]

I wonder to what maximum design speed we should limit a 44 ton truck? Or bearing in mind today’s news a 14 ton coach? Since the issue being addressed with the 20 limit is essentially a vehicle versus a pedestrian, the weight of the vehicle is pretty moot.