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 Post subject: Motorway speed control
PostPosted: Wed Jan 06, 2010 12:07 
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It seems self-evident that arbitrary numerical speed limits are based on a preposterous notion that the maximum safe speed for any stretch of road is a constant. Plainly, the maximum safe speed varies constantly with many factors such as surface condition, separation, visibility, the type of vehicle etc. I propose that, for motorways in particular, the arbitrary limit is replaced by a separation limit and clearance advice. I call it the 'speed over twenty rule' , but it includes the well known '2 second rule'. I have used it for most of my life while studiously ignoring all arbitrary speed limits and I have driven about 500,000 miles since I was last involved in an accident (1973). It's very simple.

rule 1.You NEVER come closer than 2 seconds behind the car in front. (I would replace speed cameras with separation cameras and make this an offence within the dangerous driving category).
rule 2.You divide your speed in (mph) by 20. You make sure that you can see that the road is clear (visible and unobstructed) for that many seconds in front of the car in front of you. eg. You are driving at 100mph. Check that you can see enough clear road ahead of the car in front of you for it to take at least 5 seconds for the car in front of you to get to the limit of the clear road. If not, slow down.
rule 3. If the road is wet, use the kph scale.

This might sound complicated but it isn't and, after a while, you don't even have to do the calculations because it's instinctive.


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PostPosted: Wed Jan 06, 2010 17:13 
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GrahamCresswell wrote:
rule 1.You NEVER come closer than 2 seconds behind the car in front. (I would replace speed cameras with separation cameras and make this an offence within the dangerous driving category).


What happens if another vehicle pulls in front of you within your 2 second gap just before you pass a camera?

In general your ideas are fine, however automated enforcement is always going to be problematic imho. I have no problem with a 1 second gap for brief periods, when preparing to overtake or while slowing to avoid using more braking than is really necessary as instances, a sub 2s separation is not dangerous providing a driver is aware of what is happening around them and in particular following your point about looking well ahead of the car in front.

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PostPosted: Sat Dec 04, 2010 12:31 
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Your best bet is rallying to get all the manufacturers to introduce sensors front and back which stops cars getting closer than what is required. Should youpress the accelerator within these distances it simply doesn;t respond.


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PostPosted: Sat Dec 04, 2010 14:08 
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If you had rear sensors as you say, how would these keep the car behind at a reasonable distance? Would it accellerate yours away?

In general, taking control away from the driver is a VERY BAD idea.

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PostPosted: Sat Dec 04, 2010 20:33 
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:welcome: GrahamCresswell & jogreen68
GrahamCresswell wrote:
It seems self-evident that arbitrary numerical speed limits are based on a preposterous notion that the maximum safe speed for any stretch of road is a constant. Plainly, the maximum safe speed varies constantly with many factors such as surface condition, separation, visibility, the type of vehicle etc.
I totally agree, as you are likely aware that a specific speed limit is not the safety limit. All roads are proceeded along at appropriate speeds for the constantly changing conditions. :)
Placing this interesting post in the 'Brainstorming' area lets explore your proposal.
GrahamCresswell wrote:
I propose that, for motorways in particular, the arbitrary limit is replaced by a separation limit and clearance advice. I call it the 'speed over twenty rule' , but it includes the well known '2 second rule'. I have used it for most of my life while studiously ignoring all arbitrary speed limits and I have driven about 500,000 miles since I was last involved in an accident (1973).
I can see your point about having less concentration on speed and more on preparation and better space. (The 'keeps your eyes on the road' implored motorists the always 'think' about all aspects of driving / riding.)
If you apply the 'gap distance' for motorways this will help to ensure that the 'lesson is well learned, so will be automatically continued (to a reasonable degree) on other roads, which would be good.
GrahamCresswell wrote:
It's very simple.
I can appreciate that most learn in our own ways, that suite our own abilities and attributes. For most the 2 sec rule is sufficient & simple enough to impart the safety 'rule' well.
I can see that your concept allows for varying safety distances. Is that better by 'seconds numbers' than the 'drive to observations' concepts?
However is one better or worse than another ? Does one rule give better responsibility overall and the other that relies on a speed to choose the distance, concentrate too much on the basic speed? Can & do they both teach the 'same' distance concept ? If one learns the right observation and 'drive to conditions' does it 'matter' which 'rule' got you there ?
People are all different, so does one rule limit some and benefit others or is it 'enough'.
GrahamCresswell wrote:
rule 1.You NEVER come closer than 2 seconds behind the car in front. (I would replace speed cameras with separation cameras and make this an offence within the dangerous driving category).
As Toltec has indicated the 'real world' has exceptions, so when we start saying 'never' it starts to focus over-riding importance to that 'enforcement'. After all it is human to err, with the best will in the world, 'no-one is perfect', and motoring is not that clear and precise.
We must be cautious with 'never', best practice is better and more realistic. After all police patrols that might enforce a rule can observe the 'whole picture' and we need that to ensure fairness and conditions are properly considered.
GrahamCresswell wrote:
rule 2.You divide your speed in (mph) by 20. You make sure that you can see that the road is clear (visible and unobstructed) for that many seconds in front of the car in front of you. eg. You are driving at 100mph. Check that you can see enough clear road ahead of the car in front of you for it to take at least 5 seconds for the car in front of you to get to the limit of the clear road. If not, slow down.
The faster we travel the proportionately greater the gaps, and when conditions worsen the 'even greater the gaps' to allow for the ability to stop in the distance that we know to be cleare.
What if there is no car in front of you ?
GrahamCresswell wrote:
rule 3. If the road is wet, use the kph scale.
I think for many that would confuse the issue too much,is although I appreciate that the distances would increase but is it necessary ?
As we gain experience as we drive / ride we,learn' the gaps, speeds and braking distances, in reality we understand our 'road-space'. We try really hard and mostly succeed very well not to crash into each other so we learn to be good at these learned aspects.
GrahamCresswell wrote:
This might sound complicated but it isn't and, after a while, you don't even have to do the calculations because it's instinctive.
So is it 'better' than the 2 sec rule - which for most is more simple and east to remember? If we are only on a path to teach until learned does it give an improved education?
If so what percentage of people benefit ?
Do we create more or less responsible motorists ?

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PostPosted: Sun Dec 05, 2010 09:32 
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malcolmw wrote:
If you had rear sensors as you say, how would these keep the car behind at a reasonable distance? Would it accellerate yours away?

No. It would slow you down until the gap behind was the correct two seconds.

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PostPosted: Sun Dec 05, 2010 13:55 
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dcbwhaley wrote:
No. It would slow you down until the gap behind was the correct two seconds.


How would it stop the driver behind from closing up the gap even more?

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PostPosted: Sun Dec 05, 2010 18:46 
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Pete317 wrote:
dcbwhaley wrote:
No. It would slow you down until the gap behind was the correct two seconds.

How would it stop the driver behind from closing up the gap even more?


By slowing you down even more. Until all the traffic came to a standstill when the gap would rise to infinity. So they could all set off again. Briefly, untill the sensors realised that the gap was < 2 seconds. Not a good idea.

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PostPosted: Mon Dec 06, 2010 01:52 
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dcbwhaley wrote:
No. It would slow you down until the gap behind was the correct two seconds.



And , in rain etc we could expect to see what -increased distances ,or an increase in rear enders . Especially if no allowance is made for reduced grip . From memory ,two seconds is the MINIMUM recommendation in DRY ROADS .

Any system would need some system to gauge road adhesion and adjust the two seconds according to conditions. ( something we expect a sensible driver to do anyway) .

IMHO- another dangerous route - removing more control from drivers .

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PostPosted: Tue Dec 07, 2010 00:11 
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I think that's the crux of it, to be honest. The correct time gap to leave varies with conditions, as does the correct speed. Not sure there would be much advantage in replacing one "hard and fast" rule with another that was more flexible, but also more difficult to measure / enforce. Cars are being built with short range radar as we speak, and can automatically back off if they get too close to another car. I think some have a crude adaptation to their programming that adds an arbitrary amount to the distance it allows if the wipers are switched on. As with everything else, it might weed out a few of the worst "muppets" but it might equally breed a new generation of "muppet" who just relies on it too much, so we end up back where we started.


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PostPosted: Fri Apr 15, 2011 23:39 
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malcolmw wrote:
In general, taking control away from the driver is a VERY BAD idea.


It could also be argued that taking control away from the driver would save many a road death... but hey... that probably wouldn't wash in this arena :lol:


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PostPosted: Sat Apr 16, 2011 00:01 
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I cannot see any 'device' being capable of assessing conditions and predicting an accident. The only market possible at the moment is the car sensors receiving a 'close proximity' reading and sending a 'stop' signal. That can go very wrong if stopping is not the best action and it cannot tell, eg to manoeuvre elsewhere.
But as always if you can help a motorist learn how to avoiding getting into trouble then all the 'devices' that can be invented are un-necessary.
We might like to think in this modern day and age that we can invent our way out of trouble (or control levels of trouble/danger) with technology, but the truth is that if people manage risk better and travel in a defensive manner, then they simply won't get into trouble in the first place. So showing how to be 'better' for oneself is the jey to stopping the causes of accidents.

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PostPosted: Sat Apr 16, 2011 11:32 
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Boing_uk wrote:
malcolmw wrote:
In general, taking control away from the driver is a VERY BAD idea.


It could also be argued that taking control away from the driver would save many a road death... but hey... that probably wouldn't wash in this arena :lol:

I think you might find there isn't any pragmatic automated system that will pass today's hazard perception test.
Do you agree that an automated system will brake when it is already too late, as well as "stick to the limit"?

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PostPosted: Sun Apr 17, 2011 14:59 
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Steve wrote:
I think you might find there isn't any pragmatic automated system that will pass today's hazard perception test.


Indeed. There are so many clues drivers use to anticipate hazards, about which automated systems simply wouldn't "have a clue".

Taking control away from drivers would doubtless save a few lives. But how many more would it cost?

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PostPosted: Sun Apr 17, 2011 22:20 
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I cannot really see that when you take control away from drivers that you will save a single life. How do you see that happening at all ? :)

I can see that, devices as afore-mentioned, will be more likely to cost lives than save any!

Edit : Adding that : this is against better motorist / driver appreciation as to what truly makes travel safe.

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PostPosted: Sun Apr 17, 2011 22:41 
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SafeSpeedv2 wrote:
I cannot really see that when you take control away from drivers that you will save a single life. How do you see that happening at all ?


Only in a few isolated cases where the driver is perhaps inattentive or even asleep

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I can see that devices as afore-mentioned, will be more likely to cost lives than save any!


That's precisely the point I was trying to make. I finished off with:

I wrote:
But how many more would it cost?

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PostPosted: Sun Apr 17, 2011 22:53 
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OK & I just edited my post too ! :)

Yep I fully appreciate that you know it will be a few but even if a driver is distracted or in zombie mode, is it really likely to help ?
Is the close porximity sensor able to warn than act and if it could do so from a 'better' distance might that then be 'better' ? That is can it without annoying you in other normal circumstances ... so when driving at 70mph and zombie driver fails to notice something ... shall we say ... then the sensor activating at 70mph at 50m-100m will activate an initial alert warning ? I am sure it could be speed related to distance and that might help ... warn ... :)

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PostPosted: Mon Apr 18, 2011 00:11 
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Oh I dont know - if we are talking purely motorway/expressway driving then there very well should be at the very least some form of automatic control for vehicles, if only to reduce vehicle headways and prevent ghost traffic jams. How often do we see traffic bunching up at motorway entry slips due to sheer volume? If this were managed automatically, vehicles could be slowed down upstream, gaps created etc to allow vehicles to filter in, again automatically controlled. None of this "you're not getting in front of me" mentality.

The technology does exist to detect obstructions, although not in any way adapted to motoring use. Yet. And of course it would mean a massive increase in motorways being fully monitored. But a vehicle avoiding an obstruction managed automatically is probably more likely to remain in control and on its way than an overcorrecting human behind the wheel.

Yet we are a long way off this, but automatic speed and headway management is certainly possible.


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PostPosted: Mon Apr 18, 2011 19:09 
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Boing_uk wrote:
Oh I dont know - if we are talking purely motorway/expressway driving then there very well should be at the very least some form of automatic control for vehicles, if only to reduce vehicle headways and prevent ghost traffic jams.


Yes, but....

Firstly, such a system would be expensive, even in terms of unit price.
Secondly, it would need most of the vehicles on the road to be equipped in order to be effective - this would take a very long time.
Thirdly, there are still big problems to be overcome in terms of reliable detection.
Lastly, but not leastly, it's yet another thing for (some? many?) drivers to become dependent upon.

OTOH, much the same results could conceivably be achieved with better driver education.

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PostPosted: Tue Oct 18, 2011 21:51 
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Lots of people injure themselves with kitchen knives every year. We have the technology to produce food that doesn't need preparing with sharp knives...

...I think we need to take a hard look at where we're going and actually decide whether we ought to do something just because we can! A self-driving car might suit some people but for many others it would reduce the quality of life considerably. There ar those who believe that "...if it only saves one life..." but to be honest, I thionk we have to look at the hidden costs - I don't know how we'd do it, but there is a definite (though hard to measure) benefit that comes from the freedom the motor car has brought us. We have a generation of people who now don't know what it was like before the car. Let's not chuck the baby out with the bathwater eh?


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