Safe Speed Forums

The campaign for genuine road safety
It is currently Sat Feb 29, 2020 05:06

All times are UTC [ DST ]




Post new topic Reply to topic  [ 50 posts ]  Go to page Previous  1, 2, 3
Author Message
 Post subject:
PostPosted: Mon Sep 27, 2004 16:26 
Offline
Banned
Banned

Joined: Thu Apr 15, 2004 12:47
Posts: 2291
SafeSpeed wrote:
That's not noise - that's real road safety. In far more cases still the risk is mitigated to a near miss, and in more cases than that the risk is mitigated to nothing at all.


Or it's counterpart, real road danger. If a risk occurs and no one witnesses it, was it really a risk? The philosophical points you raise are in the Zen domain, when all I want to do is slow speeders down to save them money!

SafeSpeed wrote:
There's plenty of evidence to support the idea that driver responses are getting duller in the speed camera era.


And in also in the post Tory era, and the celebrity era, and in the lottery era and in the thumb in bum era, and the quiet comfy car era and in the cheapo high performance car era and in the congested roads era and in the computer era and in the navigation system era and in the mobile phone era and the internet era and in the 'we've never been so well off' era and in the inconsiderate chump era and the tailgating era and so on and so forth. Strange that we have so many 'eras' going on, isn't it?

SafeSpeed wrote:
Cameras compel drivers to be attentive to what? Real road risks? Or cameras and speedos? If they are more attentive to cameras and speedos then they are certain to be less attentive to the road ahead. Attention is finite after all.


Attentive to their wallets, of course.

_________________
I stole this .sig


Top
 Profile  
 
 Post subject:
PostPosted: Mon Sep 27, 2004 16:43 
Offline
Site Admin
User avatar

Joined: Sat Mar 06, 2004 06:46
Posts: 16903
Location: Safe Speed
basingwerk wrote:
SafeSpeed wrote:
That's not noise - that's real road safety. In far more cases still the risk is mitigated to a near miss, and in more cases than that the risk is mitigated to nothing at all.


Or it's counterpart, real road danger. If a risk occurs and no one witnesses it, was it really a risk? The philosophical points you raise are in the Zen domain, when all I want to do is slow speeders down to save them money!


Do you really find the point so obscure? Zen? REALLY?

Look - it's simple - we have the best road safety system in the world. It functions every single time someone mitigates a real road risk. They do that hundreds of times each day (probably). It takes rampant pessimism and blinkers to only look at the crashes and forget about the normal reality. Let's improve on the existing strengths with proper messages and proper training. We know it works - it's all around us.

Cameras on the other hand lack any obvious or reliable supporting data.

basingwerk wrote:
SafeSpeed wrote:
There's plenty of evidence to support the idea that driver responses are getting duller in the speed camera era.


And in also in the post Tory era, and the celebrity era, and in the lottery era and in the thumb in bum era, and the quiet comfy car era and in the cheapo high performance car era and in the congested roads era and in the computer era and in the navigation system era and in the mobile phone era and the internet era and in the 'we've never been so well off' era and in the inconsiderate chump era and the tailgating era and so on and so forth. Strange that we have so many 'eras' going on, isn't it?


Nah look. You're cheating. We're looking for something that impinges directly on safe driving. We're looking for something that has a defined start date.

Anyway - I speak to LOADS of people who KNOW FOR SURE that their driving is adversely affected by cameras. I'd number myself amongst the group.

basingwerk wrote:
SafeSpeed wrote:
Cameras compel drivers to be attentive to what? Real road risks? Or cameras and speedos? If they are more attentive to cameras and speedos then they are certain to be less attentive to the road ahead. Attention is finite after all.


Attentive to their wallets, of course.


Just great. Shame about Little Johnny.

[edited for too many typos]

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety


Top
 Profile  
 
 Post subject:
PostPosted: Mon Sep 27, 2004 18:21 
Offline
Life Member
Life Member

Joined: Sat Mar 27, 2004 13:50
Posts: 2643
basingwerk wrote:
I’m sure you already know this, but you have asked me to explain, so I will. Going slower gives you more time before things turn critical when things do or nearly do happen. The times come from the fact that you have less speed to shed before you can come to an emergency stop, and shedding speed takes time. Furthermore, if that extra time does not enable you to avoid crashing, at least you crash at lower speed, which is in itself a good thing due to F=MA. Of course, the same applies for a dog running out, child running out, brakes fail near junction, large pothole comes into view, etc. etc.


Doesn't explain anything, really.
I take it you have some worked out examples?
Shedding speed does take time, as I pointed out, approximately 20mph/s on a dry road, which is equivalent to 40mph/s in terms of pre-braking time. (think about this one - it does make sense)
And what are those tiny fractions of a second you 'gain' by going a few mph slower really worth? Variations in your reaction time are probably far greater.


Top
 Profile  
 
 Post subject:
PostPosted: Mon Sep 27, 2004 23:18 
Offline
Life Member
Life Member

Joined: Sat Mar 27, 2004 13:50
Posts: 2643
basingwerk wrote:
I’m sure you already know this, but you have asked me to explain, so I will. Going slower gives you more time before things turn critical when things do or nearly do happen. The times come from the fact that you have less speed to shed before you can come to an emergency stop, and shedding speed takes time. Furthermore, if that extra time does not enable you to avoid crashing, at least you crash at lower speed, which is in itself a good thing due to F=MA. Of course, the same applies for a dog running out, child running out, brakes fail near junction, large pothole comes into view, etc. etc.

The error is that I only include reactions to real-world things that do happen, not to the zillions of unconnected hypothetical scenarios that do not play out because of changed timelines in a parallel world of optional events


Having read my previous reply, I decided it needed a bit more detail to put things in perspective, and to illustrate what happens in the timescales in which things turn critical, so here goes:

If you're driving along and an unexpected something happens ahead of you (say, for the purpose of this example, a tractor pulling out from a junction) the amount of time you have to react is how much time it would take from the first moment you notice the tractor pulling out to the time you would reach the junction at your current speed. If you don't react at all, this is the amount of time you have before you hit the tractor. Just to clarify a point: if you do brake it will take longer to reach the junction, by virtue of your now lower average speed, but this extra time is unavailable to you before you react.
Now, this amount of time you have available to react depends on a myriad of factors such as the precise time the tractor pulls out, what time you started out, how far you've travelled, etc etc - most of which are random and completely beyond your control, and can vary from picoseconds to hours.
But, as we're only dealing with critical situtions, let's look at times up to 3 seconds.

First, a few assumptions:

1) Your braking deceleration is 0.9g, or approx. 20mph/s
2) Your reaction time is 1 second.

So now we can work out some figures.

If you are 3 seconds away from the junction, at your current speed, you will be 3 - 1 = 2 seconds from the junction when you start braking. If your speed is such that you stop just short of the junction, and as with linear deceleration your average speed while braking is half your initial speed, it will take you 4 seconds to reach the junction - at which point you'll just have stopped.
4 seconds at 20mph/s = 80mph. So, if you're 3 seconds from the junction, your speed must be under 80mph for you to stop before the junction.
If you are 2.5 seconds from the junction, you need to be under 60mph,
2 seconds =< 40mph, 1.5 seconds =< 20mph, 1.25 seconds =< 10mph, and 1 second, < 0mph (you haven't a chance to brake)

If we now assume that your reaction time is 0.75 seconds, you can either add 10mph to all those speeds, or subtract 0.25 seconds from the times.

Note both the short time in which things become critical, and also the large equivalent change in speed for changes of fractions of a second in time - which is dependent on largely random factors and almost completely beyond your control.

If you haven't got enough time to brake to a stop, your impact speed depends on just how long you've had your foot on the brake for and, similarly, fractions of a second also make large difference to impact speed.

Are you getting the picture yet?


Top
 Profile  
 
 Post subject:
PostPosted: Tue Sep 28, 2004 09:12 
Offline
Banned
Banned

Joined: Thu Apr 15, 2004 12:47
Posts: 2291
Pete317 wrote:
And what are those tiny fractions of a second you 'gain' by going a few mph slower really worth? Variations in your reaction time are probably far greater


I'd prefer it if you were going many mph slower to gain large fractions of a second, but anyway, a reaction time of 2 seconds at 40 mph covers a constant distance of around 120 feet, and at 30, 30 feet less. Just by obeying the law, you have 30 feet of extra margin for avoidance and emergency stops in these terms! And that is with a 2 second reaction time. Any more than that and you are talking about very long distances. A crash happens only in the last foot!

_________________
I stole this .sig


Top
 Profile  
 
 Post subject:
PostPosted: Tue Sep 28, 2004 09:27 
Offline
Site Admin
User avatar

Joined: Sat Mar 06, 2004 06:46
Posts: 16903
Location: Safe Speed
basingwerk wrote:
I'd prefer it if you were going many mph slower to gain large fractions of a second, but anyway, a reaction time of 2 seconds at 40 mph covers a constant distance of around 120 feet, and at 30, 30 feet less. Just by obeying the law, you have 30 feet of extra margin for avoidance and emergency stops in these terms! And that is with a 2 second reaction time. Any more than that and you are talking about very long distances. A crash happens only in the last foot!


Why do you persist in assuming that reaction times are likely to be the same at the "new" lower speed? here are two critically important reasons why we should expect reactions to be slower at a reduced speed dictated by enforcement:

1) The distraction effect of enforcement and the risk of enforcement. I keep telling you that speed cameras alter drivers' visual scans. We look for cameras even where there are none and we check our speedos more often.

2) The new lower speed is less demanding of attention and less attention is given.

If you think reaction times are preserved, quote your evidence.

_________________
Paul Smith
Our scrap speed cameras petition got over 28,000 sigs
The Safe Speed campaign demands a return to intelligent road safety


Top
 Profile  
 
 Post subject:
PostPosted: Tue Sep 28, 2004 09:42 
Offline
Banned
Banned

Joined: Thu Apr 15, 2004 12:47
Posts: 2291
SafeSpeed wrote:
The new lower speed is less demanding of attention and less attention is given


And that is where you come in, SafeSpeed. Your campaign for awareness is laudible. I want lower speeds AND more attention.

_________________
I stole this .sig


Top
 Profile  
 
 Post subject:
PostPosted: Tue Sep 28, 2004 11:07 
Offline
Member
Member
User avatar

Joined: Sat Mar 20, 2004 09:59
Posts: 3544
Location: Shropshire
basingwerk wrote:
SafeSpeed wrote:
The new lower speed is less demanding of attention and less attention is given


And that is where you come in, SafeSpeed. Your campaign for awareness is laudible. I want lower speeds AND more attention.


When the great speed clampdown began it was perhaps with the intention of simply lowering average speeds across the road system. Unfortunately the reaction to the elevated risk of getting caught doing what they (we) had previously done, more or less, with impunity has been somewhat predictable.
Thus, instead of creating a nation of slower, alert drivers a completely different behaviour has emerged, one that has been turned over as often as a pork chop on the barbeque within this forum alone.
However, simply because most people are law abiding and well meaning doesn't mean our overall attitude isn't steering us on a course of self-destruction. We are often being told we eat too much of the wrong food, drink too much, spend too much on our credit cards, bring our children up wrongly and of course drive incorrectly.
Does it make any difference? - Nope
Does it mean that everyone will pay attention and change their habits? - Niet
So, is everybody stupid then? Whether they are or aren't, preaching and clubbing people with a big stick tends to engeander belligerence not compliance.


Top
 Profile  
 
 Post subject:
PostPosted: Tue Sep 28, 2004 11:20 
Offline
Member
Member

Joined: Thu Mar 11, 2004 00:24
Posts: 2400
Location: Kendal, Cumbria
Rigpig wrote:
So, is everybody stupid then? Whether they are or aren't, preaching and clubbing people with a big stick tends to engeander belligerence not compliance.

Bang on!

What the HSE realised about 20 years ago (if not more) was that the key to improving safety was to devolve more responsibility into people's own hands, to empower them to make balanced decisions about how best to ensure their own safety and that of others around them.

That has been a cornerstone of Industrial Safety ever since, and it has worked miracles.

Unfortunately Road Safety has chosen to stride off in the exact opposite direction over the last ten years, in pursuit of what we can only assume to be hidden political agendas. We are already reaping the grim rewards of this backward looking policy in terms of the steady upturn of the fatality trends over the last ten years; this can surely only worsen as long as this flawed logic is foisted upon us.

_________________
CSCP Latin for beginners...
Ticketo ergo sum : I scam therefore I am!


Top
 Profile  
 
 Post subject:
PostPosted: Tue Sep 28, 2004 12:57 
Offline
Life Member
Life Member

Joined: Sat Mar 27, 2004 13:50
Posts: 2643
basingwerk wrote:
Pete317 wrote:
And what are those tiny fractions of a second you 'gain' by going a few mph slower really worth? Variations in your reaction time are probably far greater


I'd prefer it if you were going many mph slower to gain large fractions of a second, but anyway, a reaction time of 2 seconds at 40 mph covers a constant distance of around 120 feet, and at 30, 30 feet less. Just by obeying the law, you have 30 feet of extra margin for avoidance and emergency stops in these terms! And that is with a 2 second reaction time. Any more than that and you are talking about very long distances. A crash happens only in the last foot!


No you haven't got that extra margin. You can't have something you didn't have in the first place.
You obviously either didn't read my second posting, you chose to ignore it, or you dismissed it as rubbish because you cannot understand the concepts. In that case I suggest you re-read it until it dawns on you what I'm getting at.
Clue: the laws of probability. The probability of you being between any two points along the road at any particular time is directly proportional to the time you spend between those two points. (which, incidentally, is inversely proportional to your speed in between those points) You cannot establish any principles by merely placing yourself at a convenient fixed point along the road.
Also, the laws of physics: you cannot change the speed of a moving object without also changing it's position at a given time.


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 50 posts ]  Go to page Previous  1, 2, 3

All times are UTC [ DST ]


Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group
[ Time : 0.257s | 11 Queries | GZIP : Off ]