20mph speed limit called for in towns

[detective-boy]

"Lowering the speed limit to 20mph reduces total road traffic casualty levels by around 60% and child casualties by around 70% according to studies in both Britain and Denmark."

Compared to what?

On it's own that is an entirely meaningless statistic.

 

[untethered]

Yes. But why stop there? Why not go to 10mph? Or 5mph? Or ban cars? Or make pedestrians stay in bed?

It is a balance, not one absolute. A question of proportionality.

Below a certain point, the benefits of owning a car largely disappear.

Some may see this as a good thing but either way it's not likely to be broadly acceptable.

20mph is a good compromise point that has many safety and social benefits (including for drivers and their passengers) with no significant difference in urban journey times.

 

[Paulie Tandoori]

Compared to what?

On it's own that is an entirely meaningless statistic.

Compared to the number of accidents that occured before the reduction in the speed limit.

 

[Paulie Tandoori]

That does not tell us how many fatal crashes there were in the two types of zones.

Also, as others have pointed out, it is possible that the 20mph zones were more at risk and that's why they were 20mph zones.

It does appear to show the numbers overall.

2006 figures (tab.4 Accidents: by road class, speed limit and severity: 1994-98 average1, 1999 - 2006)
A Roads
20 mph limit:

Fatal - 0
Fatal and serious - 23
All severities - 119

30 mph limit:

Fatal - 370
Fatal and serious - 5,745
All severities - 44,733

Other roads
20 mph limit:

Fatal - 15
Fatal and serious - 146
All severities - 877

30 mph limit:

Fatal - 539
Fatal and serious - 9,517
All severities - 73,741

So in purely numerical terms, you have more than 5,000 fatal and serious accidents in 30pmh zones on A roads, compared to 23 in 20 mph zones, whereas on other roads, the comparative figures are 9,500 fatal and serious in 30mph against 146 on 20 mph. Looks pretty convincing to me.

 

[chymaera]

Looks pretty convincing to me.

Not convincing at all without knowing the mileages of road in each limit and the traffic useage.

 

[Crispy]

As percentages of total severities, the death rates are:

A roads:

20mph: 0%
30mph: 0.82%

Other Roads

20mph: 1.7%
30mph: 0.7%

All this shows is that Other roads where 20mph limits are in place are over twice as likely to kill you if you have an accident.

What it doesn't tell you is if that likelyhood is due to the 20mph limit, or due to the pre-existing dangers that caused a 20mph to be installed in the first place.

Knowing the effect of imposing 20mph limit (or strictly enforcing a 30mph limit) can only be done by doing on-site data collection over a number of areas, before and after the enforcement.

 

[detective-boy]

20mph is a good compromise point that has many safety and social benefits (including for drivers and their passengers) with no significant difference in urban journey times.

Your evidence for "no significant difference"?

(Particularly in relation to things like transport costs for deliveries, which would have a 50% increase in time whenever 30mph was safe and possible which would be a significant amount of the time, not least at night)

 

[detective-boy]

Compared to the number of accidents that occured before the reduction in the speed limit.

Do you know that? Please link to the original research report which states that is the baseline from which the 60%/70% reduction is measured.

 

[detective-boy]

Looks pretty convincing to me.

Bearing in mind that there are many, many times more 30mph miles of road than 20mph miles of road, and the majority of 20mph roads are the very low usuage estate roads, etc, or very short stretches outside schools or whatever, do you not think it would be wise to ask how many vehicle miles travelled these statistics refer to?

 

[Paulie Tandoori]

Do you know that? Please link to the original research report which states that is the baseline from which the 60%/70% reduction is measured.

Of course i don't know that but an educated guess would indicate that this is most likely baseline.

What do you suggest they measured it against? Traffic flow in Edwardian times, road accidents in ruislip, car crashes in Carshalton?

 

[citydreams]

Bearing in mind that there are many, many times more 30mph miles of road than 20mph miles of road

 

[goldenecitrone]

As a compromise how about this. 20 mile per hour speed limit in towns and cities but you can drive as fast as you like on motorways. Fuck, you can even put wings on the side of your car and attempt take-off you Clarkson's cock-sucking speed freaks.

 

[subversplat]

KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!
KILL ALL NANNY STATE FUCKING LIBERALS!!!

You seem hysterical.

I remember a post about that....

 

[detective-boy]

Of course i don't know that but an educated guess would indicate that this is most likely baseline.

They could have compared it against any number of different things, all of which would be potentially relevant.

ymu will be along in a minute I'm sure, to explain that, in statistical terms, you need to know what the baseline is (in detail) before you can make any judgment on the relevance of a "60% reduction" claim.