Petition: 30 km/h (20 mp/h) urban speed limit

[SquareDaff]

[QUOTE 2332749, member: 45"]You'd think this was the answer, but it's never worked. The HC and the driving test cover the education, but still many drivers think they know better.

It's not about knowledge, but attitude.[/quote]
I remember during my lessons - my instructor told me I had to drive at the posted speed limit if I was to pass my test - otherwise the examiners would fail me for driving too slowly. If this attitude was prevalent among the instructors in my region (and possibly nationally) it's no wonder people drive the way they do. If it's still taught that way now then we have a massive problem.

 

[Linford]

[QUOTE 2332873, member: 45"]If you want to be taken seriously I'd suggest you don't make stuff up.

My thread was the perfect illustration -driver attitude preventing things workign as they should.[/quote]

It's quite simple as I see it really, you wanted to join the flow of the traffic, no gaps in it, you got fed up and whizzed into it putting someones nose out of joint as they felt you were taking a liberty with their safe braking zone ...who then got iffy with you.
I see it day in and day out . I blame the system....

 

[Linford]

[QUOTE 2332917, member: 45"]I refer you to post #39. Don't be an idiot and derail the thread.[/quote]


Seriously though, if all traffic is slowed down from 30mph to 20mph, then the capacity of the road is reduced by 1/3rdb (ish)

It stands to reason that if you had the same traffic levels on it, a slower road will spend more time being occupied by that number for a longer period of time as the traffic takes a 1/3rd longer time to traverse it . You will get faster traffic more spaced out, or slower traffic all stood still

 

[wiggydiggy]

[QUOTE 2332937, member: 45"]I think Linf just posted. Can someone tell him he's got a spell on my ignore list?[/quote]

You just did Your ignoring his posts, not him ignoring yours...

 

[Linford]

Why? Does the road space shrink as the speed limit reduces? Or do more cars magically appear as the speed limit reduces?

You really haven't thought this through, have you? Shall I ask a five year old to explain it to you with some crayons and a couple of toy cars?

Are you so sure you have ?

If the number of cars using the road doesn't change but the time which it takes them to traverse it does....and you then knock 1/3rd off that duration (by going from 20mph to 30mph), you actually increase the theoretical capacity of the road by 33% or if the spacings between them at 20mph are even, you increase those spacings.in the same time frame because the cars themselves don't change in size.

 

[green1]

Why? Does the road space shrink as the speed limit reduces? Or do more cars magically appear as the speed limit reduces?

You really haven't thought this through, have you? Shall I ask a five year old to explain it to you with some crayons and a couple of toy cars?

In this case he is right. Capacity of a road is reduced as you reduce the speed limit unless you increase the amount of lanes.

 

[Linford]

Or put another way, if the road can take 100 cars, and only 1 can leave the end of it each minute, speed the flow up so 4 can leave it each minute and you quadruple the capacity. This is why gridlock traffic jams can only cope with the numbers of vehicles in them...because you can't add any more to it.

I thought you were some sort of accountant/auditor dude Reg ?

 

[Linford]

Really? Are you sure about that? Do you want to sit and have a think about what you're suggesting? Perhaps read back on some of the earlier posts?



You have changed the laws of physics. Someone call the Nobel Committee!

I've explained why I feel the argument is flawed, feel free to offer a bit more detail as I just am not seeing your case standing up to scrutiny/

 

[green1]

Really? Are you sure about that? Do you want to sit and have a think about what you're suggesting?

Think of it in simplistic terms: Think of a road as a conveyor belt filling a hopper, the belt can only take a tonne per meter, what would happen to the capacity (tonnes per hour) if you slowed the speed that the belt was operating at from 30 mph to 20 mph? It would reduce as the time it takes to traverse the belt increases. Okay safe distances between vehicles would reduce but not significantly.

 

[Linford]

Think again about the analogy you're using and what Linford was suggesting (see posts passim).

How does mine deviate ?

 

[Linford]

You're the one suggesting that the capacity of a road is reduced if you lower the speed limit on it. You're being asked to evidence this assertion.

So far you are floundering to say the least....

Let me put this another way.

Put a bottle neck on it which chokes the exit to 200 cars per hour, modify the bottle neck to ease the problem and that then lets the traffic flow faster....300 cars per hour. It can't get much simmpler than that...
slower = less
faster = more

Come on Reg, it isn't rocket science

 

[Dan B]

In this case he is right. Capacity of a road is reduced as you reduce the speed limit unless you increase the amount of lanes.

... or reduce the space between each car. Which, spookily, is what happens if you slow them down - and, exponential functiuons being what they are, by more than the loss due to slowing them down.

I expect I'll now be told that in Safespeed-world it takes less than double the distance to brake from 60 to 0 than from 30 to 0, but that's not what the back cover of the highway code used to say

 

[Spinney]

Leaflet through the door from the LibDems the other week, with news from MP, LD councillors etc.

One article was about putting a pedestrian crossing in a local village that has a B road going through it. There is a 30 limit there, and I think it might be one of those places with a 20 limit at the beginning and end of the school day.

The end of the debate was that they could not put a crossing there because the traffic was too fast, averaging 42 mph. (I presume there is some issue about the time drivers have to react from the point at which they can see the crossing?).

So, rather than propose measures to make drivers obey the speed limit, the conclusion was that no, you cannot make the road safer to cross by having a crossing.

 

[snorri]

I've explained why I feel the argument is flawed,

The argument is not one of achieving maximum road capacity, but of improving safety for all users. The optimum speed for maximum capacity appears to be 25-30mph, so lowering the speed limit to 20mph improves safety for all users with the possibility of increased delays only on the roads which are already at or near capacity This makes use of that road less attractive for motor vehicle drivers, thus discouraging those drivers who make unnecessary trips . Sounds good to me.

 

[Linford]

What bottleneck? A speed limit isn't a bottleneck.

You've got to try harder or you'll end up on my 'Too Thick to Bother With' list...

Have you not heard of the caterpillar effect ?