Misinformation on SACs
Discussion
Well I got through it again (note so self don't get caught again, you twonk) last night in Chesterfield. And it was interesting to compare to the AADrivetech one I did 3 years ago. The tutors(?) where much better. One was really good, but the other was a bit knobby talking over anything (anyone) he didn't want to hear.
The sections on speed limits and hazard awareness were actually quite good with a focus on safe speed, observation and stopping.
The core premise of course was horrible. Based on the fact that in vid, Tiff could stop at 30mph but it all went wrong for the cardboard dummy at any speeds over 30 (no s
t), that was a definitive argument for the dangers of 'marginal speeding'. I have to admire the almost evangelical way that connection was taken through the course. And when we did the 'what are the consequences of hitting a ped' role play (which was actually quite powerful), the full appalling-ness of marginal speeding became apparent. And yes at the end with a choice of dangerous or not dangerous, I had to vote that marginal speeding is not dangerous.
One of the dudes claimed that if he was in free flowing normal motorway traffic at 70 and the variable limit sign came on at 20, he would slow to 20 without any question or regard to what was going on behind.
And to the interesting facts...
Airbags don't go off if you don't wear a seatbelt
In a 30 you should be in 3rd for better fuel consumption, because... if you select 4th, your modern ecu sees that and thinks you want to go faster because that is what 4th is for
Smart motorways automatically reduce speeds for noise or pollution levels
Driving between 7pm and 7am is the most dangerous part of the day
Hey ho, all good fun.
Bert
The sections on speed limits and hazard awareness were actually quite good with a focus on safe speed, observation and stopping.
The core premise of course was horrible. Based on the fact that in vid, Tiff could stop at 30mph but it all went wrong for the cardboard dummy at any speeds over 30 (no s
t), that was a definitive argument for the dangers of 'marginal speeding'. I have to admire the almost evangelical way that connection was taken through the course. And when we did the 'what are the consequences of hitting a ped' role play (which was actually quite powerful), the full appalling-ness of marginal speeding became apparent. And yes at the end with a choice of dangerous or not dangerous, I had to vote that marginal speeding is not dangerous.One of the dudes claimed that if he was in free flowing normal motorway traffic at 70 and the variable limit sign came on at 20, he would slow to 20 without any question or regard to what was going on behind.
And to the interesting facts...
Airbags don't go off if you don't wear a seatbelt
In a 30 you should be in 3rd for better fuel consumption, because... if you select 4th, your modern ecu sees that and thinks you want to go faster because that is what 4th is for
Smart motorways automatically reduce speeds for noise or pollution levels
Driving between 7pm and 7am is the most dangerous part of the day
Hey ho, all good fun.
Bert
BertBert said:
Airbags don't go off if you don't wear a seatbelt
Is this true? because I find it difficult to believe, especially as in some countries (some of USA?) there is no requirement to wear seat belts but cars still have airbags. 
As for the 3rd gear b
ks, my car's an auto and would likely be in 5th gear at 30mph so how does that work?....Riley Blue said:
EU_Foreigner said:
Tiff driving a Morris Minor by any chance? Bet a new Golf would still stop at twice the speed in the same distance ...
Or in half the distance from the same speed...
Tiff was in a focus ST. It doesn't matter the car, as the point of the video was to compare stopping distances from different speeds along with the speed you are still going at when the slower car has stopped. So the car that was doing 100mph was still doing (IIRC) over 70 when the car that was doing 70 has stopped. All good and interesting.
The problem is that the fact that the car doing 30 could stop before the cardboard cutout and the same car doing > 30 couldn't stop then formed the basis of the rest of the course to show why exceeding the speed limit was bad and keeping to it was good. Of course my suggestion that it was an artificially constructed argument was well and truly talked over!
The problem is that the fact that the car doing 30 could stop before the cardboard cutout and the same car doing > 30 couldn't stop then formed the basis of the rest of the course to show why exceeding the speed limit was bad and keeping to it was good. Of course my suggestion that it was an artificially constructed argument was well and truly talked over!
EU_Foreigner said:
Tiff driving a Morris Minor by any chance? Bet a new Golf would still stop at twice the speed in the same distance ...
No, it's not true.
What is true is that airbags are much better at their job when the occupant is nicely held in the seat by the seatbelt (and not holding the top of the wheel with one hand). The concept that they are enabled by plugging in the seatbelt is tosh.
As for the 3rd gear bks, my car's an auto and would likely be in 5th gear at 30mph so how does that work?....
What is true is that airbags are much better at their job when the occupant is nicely held in the seat by the seatbelt (and not holding the top of the wheel with one hand). The concept that they are enabled by plugging in the seatbelt is tosh.
catso said:
BertBert said:
Airbags don't go off if you don't wear a seatbelt
Is this true? because I find it difficult to believe, especially as in some countries (some of USA?) there is no requirement to wear seat belts but cars still have airbags. As for the 3rd gear b
ks, my car's an auto and would likely be in 5th gear at 30mph so how does that work?....catso said:
BertBert said:
Airbags don't go off if you don't wear a seatbelt
Is this true? because I find it difficult to believe, especially as in some countries (some of USA?) there is no requirement to wear seat belts but cars still have airbags. However an airbag system does operate in conjunction with the passive safety systems in the car - such as the seatbelt - in that the intention is that the airbag is *deflating* when you hit it. Without a seatbelt on you're likely to impact earlier, possibly even when the airbag is still inflating, and therefore subject to injury.
BertBert said:
Tiff was in a focus ST. It doesn't matter the car, as the point of the video was to compare stopping distances from different speeds along with the speed you are still going at when the slower car has stopped. So the car that was doing 100mph was still doing (IIRC) over 70 when the car that was doing 70 has stopped. All good and interesting.
Not when, but where it stopped.Stuzza said:
However an airbag system does operate in conjunction with the passive safety systems in the car - such as the seatbelt - in that the intention is that the airbag is *deflating* when you hit it. Without a seatbelt on you're likely to impact earlier, possibly even when the airbag is still inflating, and therefore subject to injury.
A mate of mine can attest to this. He was the passenger in a car involved in an accident where the airbags fired. Driver was wearing a seatbelt, got a bit of a shock, and some airbag dust on his face, but otherwise OK. Passenger (my mate) was not wearing a seatbelt. Airbag gave him such severe whiplash, he was off work for about a fortnight whilst he recovered.I'm assuming this is because the impact of the accident forced him forward (unrestrained), and the airbag forced him back (very, very quickly).
vonhosen said:
BertBert said:
Tiff was in a focus ST. It doesn't matter the car, as the point of the video was to compare stopping distances from different speeds along with the speed you are still going at when the slower car has stopped. So the car that was doing 100mph was still doing (IIRC) over 70 when the car that was doing 70 has stopped. All good and interesting.
Not when, but where it stopped.TwigtheWonderkid said:
Yup, car doing 70 mph carries 1/2 mass velocity squared units of kinetic energy. Ignore mass and the 1/2 from both sides of the equations as we're talking about identical cars so just use velocity. 70 squared = 4900 units. car doing 100 carries 10K units. So when the car doing 100 gets to where car doing 70 stopped, it's scrubbed off 4900 units, leaving 5100 units of kinetic energy still in it. Square root of that is the speed, 71.41mph.
That might be of some relevance if the speed limit down the High Street was 70 and you were trying to deter people from doing 100.When is the last time someone stepped out in front of you on the Motorway?
BertBert said:
Tiff was in a focus ST. It doesn't matter the car, as the point of the video was to compare stopping distances from different speeds along with the speed you are still going at when the slower car has stopped. So the car that was doing 100mph was still doing (IIRC) over 70 when the car that was doing 70 has stopped. All good and interesting.
The problem is that the fact that the car doing 30 could stop before the cardboard cutout and the same car doing > 30 couldn't stop then formed the basis of the rest of the course to show why exceeding the speed limit was bad and keeping to it was good. Of course my suggestion that it was an artificially constructed argument was well and truly talked over!
Why go on the course just to argue? On the one I attended a few months ago, the ground rules were clear, either engage constructively, or be thrown out and get the points & fine. The premise of their argument is good around the stopping distance. Just because you don't agree with the speed limit that's set doesn't make their point invalid. The cardboard cutout (ok it'd be a person) could step out expecting traffic to be travelling at or around the speed limit, rather than a speed that a driver has notionally chosen for themselves. The problem is that the fact that the car doing 30 could stop before the cardboard cutout and the same car doing > 30 couldn't stop then formed the basis of the rest of the course to show why exceeding the speed limit was bad and keeping to it was good. Of course my suggestion that it was an artificially constructed argument was well and truly talked over!
BertBert said:
Well I got through it again (note so self don't get caught again, you twonk) last night in Chesterfield..........
Blah blah blah
One of the dudes claimed that if he was in free flowing normal motorway traffic at 70 and the variable limit sign came on at 20, he would slow to 20 without any question or regard to what was going on behind.
Interestingly I was on the M1 approaching J29 at Chez Vegas last week well after dark when the variable signs suddenly showed '50' for no obvious reasonBlah blah blah
One of the dudes claimed that if he was in free flowing normal motorway traffic at 70 and the variable limit sign came on at 20, he would slow to 20 without any question or regard to what was going on behind.
I slowed to be compliant but an Audi (what else) steamed past me and the nearest gantry at an estimated 70mph followed by the most fantastic shock and awe moment as the cameras went off and lit up most of Derbyshire
So if they say '20' then on the strength of this Im gonna do 20
Cheers
cmaguire said:
TwigtheWonderkid said:
Yup, car doing 70 mph carries 1/2 mass velocity squared units of kinetic energy. Ignore mass and the 1/2 from both sides of the equations as we're talking about identical cars so just use velocity. 70 squared = 4900 units. car doing 100 carries 10K units. So when the car doing 100 gets to where car doing 70 stopped, it's scrubbed off 4900 units, leaving 5100 units of kinetic energy still in it. Square root of that is the speed, 71.41mph.
That might be of some relevance if the speed limit down the High Street was 70 and you were trying to deter people from doing 100.When is the last time someone stepped out in front of you on the Motorway?
Given that people do do 100mph on the motorway, it's shocking to find out that when they hit the brakes having just noticed the traffic ahead is backed up, if they would have stopped an inch short from 70, they will hit the first car at 71 from 100mph.
Edited by TwigtheWonderkid on Thursday 13th April 21:47
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