Speed awareness course feedback
Discussion
TwigtheWonderkid said:
George Smiley said:
You haven’t included friction to your calculations
You are working it out that both the cortina and the 911 have the same coefficients, brakes nor are you taking into consideration weight distribution, spring rates etc.
No, I'm saying that the Cortina at 30 mph has the same brakes, weight distribution and springs as the self same Cortina at 35 mph, and the 911 at 30 has the same brakes, weight distribution and springs as the self same 911 at 35 mph. You are working it out that both the cortina and the 911 have the same coefficients, brakes nor are you taking into consideration weight distribution, spring rates etc.
We are talking about the same incident. A Cortina braking from 30mph at point A comes to a halt at point B. Had it been doing 35mph at point A, it would be doing 18mph at point B. Same for a 911 (although point B will be closer to point A for the 911.)
People can argue this until the cows come home, but they are wrong, and Sir Isaac Newton was right. The laws of physics don't give two hoots if a human thinks they don't sound right.
vonhosen said:
In practice people also tend to over estimate the distance they need available to stop within at low speeds, but under estimate it at high speeds.
Agreed. It's quite interesting to do a full emergency stop from high speed. Most people probably never have done and only ever did an emergency stop from 25mph on their test, although will drive very close to the car in front at speed and with no escape routes.
Many bikers apparently fall off when they first time they do a high speed stop is to avoid a hazard - I made sure I practiced.
Autobahn driving as a Brit unleashed requires a lot of space.
blueacid said:
The second thing which got me was when the instructor was searching for other ways to determine the speed limit if a sign wasn't immediately visible. Clues like streetlights, street markings, houses etc already offered. I ventured "My satnav app often has speed limit information and displays this". I had apparently stumbled on the trigger-words for a well-rehearsed patter between the two course officiators, names changed because they weren't memorable: "Oh, sometimes these apps can be wrong, the data's wrong isn't it Bob?", "It absolutely is Alice, these databases are often out of date", "Quite right Bob, it's really very unreliable" (nods from Bob)... "No, to rely on your sat nav is really no use at all, definitely don't rely on it". Never said anything about 'relying' on it. I said nothing, just decided to let the time continue to agonisingly pass.
To be honest the rehearsed patter and the patronising delivery did detract from what might have been useful information. I saw a few derisory shakes of the head around the room. The instructors did have the chance to get us on board, think they binned it for a few in the room at that point.
I wonder how many people do rely on it though?To be honest the rehearsed patter and the patronising delivery did detract from what might have been useful information. I saw a few derisory shakes of the head around the room. The instructors did have the chance to get us on board, think they binned it for a few in the room at that point.
My old Skoda had that feature, and the passage of time meant it was out of date pretty quickly. Even my dad’s 2 year old Toyota is out of date already on a few roads local to us, obviously we know there was all the hoo-ha about them changing from 70 down to 50, but would ‘non-natives’? It’s another excuse they could probably try and use when they get caught over the limit... compo face coming to a local paper near you soon!
TwigtheWonderkid said:
vonhosen said:
It is to illustrate that people more often than not under estimate what that residual speed will be.
Absolutely. Loads of people do 100 on the motorway. My mum does and thinks it's fine. But ask someone if they slam on their brakes at 70 to avoid the queue of traffic ahead and come to a halt a whisker from the car at the end of the queue, what speed would they have ploughed into that car had they been doing 100, none of them will know it's 71 mph. In the distance it takes a car to get down from 70 to zero, the same car won't have got down to 70 from 100. Because 100 squared is 10K, 70 squared is 4900, so the car travelling at 100mph still has 5100 units to scrub off at the point they would have scrubbed off 4900 had they been doing 70. And the square root of 5100 is.......71 and a bit.
You're also assuming the gap between the cars is identical to "thinking distance" and that car B doesn't brake until he sees car A brake, when in reality car B may well be looking much further ahead.
...and that is the problem with theory.
TwigtheWonderkid said:
vonhosen said:
It is to illustrate that people more often than not under estimate what that residual speed will be.
Absolutely. Loads of people do 100 on the motorway. My mum does and thinks it's fine. But ask someone if they slam on their brakes at 70 to avoid the queue of traffic ahead and come to a halt a whisker from the car at the end of the queue, what speed would they have ploughed into that car had they been doing 100, none of them will know it's 71 mph. In the distance it takes a car to get down from 70 to zero, the same car won't have got down to 70 from 100. Because 100 squared is 10K, 70 squared is 4900, so the car travelling at 100mph still has 5100 units to scrub off at the point they would have scrubbed off 4900 had they been doing 70. And the square root of 5100 is.......71 and a bit.
You're also assuming the gap between the cars is identical to "thinking distance" and that car B doesn't brake until he sees car A brake, when in reality car B may well be looking much further ahead.
...and that is the problem with theory.
havoc said:
You're assuming both cars have identical braking capabilities, AND both drivers are using 100% of those capabilities (unlikely - most drivers don't use full braking even in an emergency stop).
You're also assuming the gap between the cars is identical to "thinking distance" and that car B doesn't brake until he sees car A brake, when in reality car B may well be looking much further ahead.
...and that is the problem with theory.
Yep, it’s binary thinking. You're also assuming the gap between the cars is identical to "thinking distance" and that car B doesn't brake until he sees car A brake, when in reality car B may well be looking much further ahead.
...and that is the problem with theory.
havoc said:
TwigtheWonderkid said:
vonhosen said:
It is to illustrate that people more often than not under estimate what that residual speed will be.
Absolutely. Loads of people do 100 on the motorway. My mum does and thinks it's fine. But ask someone if they slam on their brakes at 70 to avoid the queue of traffic ahead and come to a halt a whisker from the car at the end of the queue, what speed would they have ploughed into that car had they been doing 100, none of them will know it's 71 mph. In the distance it takes a car to get down from 70 to zero, the same car won't have got down to 70 from 100. Because 100 squared is 10K, 70 squared is 4900, so the car travelling at 100mph still has 5100 units to scrub off at the point they would have scrubbed off 4900 had they been doing 70. And the square root of 5100 is.......71 and a bit.
You're also assuming the gap between the cars is identical to "thinking distance" and that car B doesn't brake until he sees car A brake, when in reality car B may well be looking much further ahead.
...and that is the problem with theory.
ie whatever vehicle you're personally driving, in whatever conditions, with whatever reaction time you are going to be carrying a higher residual speed than you probably appreciated at the point where you'd have stopped had you been travelling at a slower initial speed (in those conditions with that reaction time).
That's in practice, not theory.
Then it's not relative to me or anyone else, it's solely about the effects for you with varying initial speeds you are carrying.
I learnt a fair bit when I went on the speed awareness course although it was some 10 years ago mind.
I'd like to think the biggest factor in a change of driving habits has been since having children.
My current car is the first with a speed limiter. I regularly set it to 70. I see many a car fly past me at 80+ but still only end up slightly in front of me in the queues when coming off the motorway maybe prob 10-15 miles down the road.
I'd like to think the biggest factor in a change of driving habits has been since having children.
My current car is the first with a speed limiter. I regularly set it to 70. I see many a car fly past me at 80+ but still only end up slightly in front of me in the queues when coming off the motorway maybe prob 10-15 miles down the road.
I have no issue with obeying speed limits, as silly as some of them seem to be. What I do have an issue with is the inevitability of some twunt sitting two inches off my back bumper, like their life's purpose is now to express that me not breaking the law and risking a fine and points is somehow an affront to them. I wish the authorities would do something about that.
Johnnytheboy said:
I have told this before... had a really posh but utterly potty mouthed bloke on my table sat next to the most council woman on earth. They seemed to get on famously.
We watched that "speeding is bad" safety film with the guy who keeps seeing the body of the red haired kid that he ran over everywhere.
The lights went up and the ghastly woman who was running things said "that was harrowing wasn't it?"
To which Ms Council blurts out "I know right? That kid was really ginger."
Posh bloke guffaws really loudly and the whole room starts laughing.
LOL! If I’d been drinking coffee it would be all over my bloody ipad now!We watched that "speeding is bad" safety film with the guy who keeps seeing the body of the red haired kid that he ran over everywhere.
The lights went up and the ghastly woman who was running things said "that was harrowing wasn't it?"
To which Ms Council blurts out "I know right? That kid was really ginger."
Posh bloke guffaws really loudly and the whole room starts laughing.
Funny
havoc said:
TwigtheWonderkid said:
vonhosen said:
It is to illustrate that people more often than not under estimate what that residual speed will be.
Absolutely. Loads of people do 100 on the motorway. My mum does and thinks it's fine. But ask someone if they slam on their brakes at 70 to avoid the queue of traffic ahead and come to a halt a whisker from the car at the end of the queue, what speed would they have ploughed into that car had they been doing 100, none of them will know it's 71 mph. In the distance it takes a car to get down from 70 to zero, the same car won't have got down to 70 from 100. Because 100 squared is 10K, 70 squared is 4900, so the car travelling at 100mph still has 5100 units to scrub off at the point they would have scrubbed off 4900 had they been doing 70. And the square root of 5100 is.......71 and a bit.
You're also assuming the gap between the cars is identical to "thinking distance" and that car B doesn't brake until he sees car A brake, when in reality car B may well be looking much further ahead.
...and that is the problem with theory.
I don't know how I can make this any clearer. Archie Roberts was driving his Passat on the M1 yesterday at 3pm, doing 70mph, when he had to slam on his brakes to avoid the queue of traffic ahead, and came to a halt a whisker from the car at the end of the queue. Then he thinks to himself......I wonder what would have happened if I, Archie Roberts, in my Passat at 3pm on the M1, had being doing 100 when I slammed on the brakes, instead of 70.
That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph.
Yonex is never going to get it, because to be frank, it's well beyond him, but I was kind of hoping others would. This really is schoolboy physics. You don't need to be Prof Brian Cox to grasp it.
TwigtheWonderkid said:
There is no car A and car B. there's only 1 car, one driver and 1 incident. There is no thinking distance to be considered, because we're talking about events post thinking distance, when you hit the brakes.
I don't know how I can make this any clearer. Archie Roberts was driving his Passat on the M1 yesterday at 3pm, doing 70mph, when he had to slam on his brakes to avoid the queue of traffic ahead, and came to a halt a whisker from the car at the end of the queue. Then he thinks to himself......I wonder what would have happened if I, Archie Roberts, in my Passat at 3pm on the M1, had being doing 100 when I slammed on the brakes, instead of 70.
That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph.
Yonex is never going to get it, because to be frank, it's well beyond him, but I was kind of hoping others would. This really is schoolboy physics. You don't need to be Prof Brian Cox to grasp it.
Absolutely correct. I don't know how I can make this any clearer. Archie Roberts was driving his Passat on the M1 yesterday at 3pm, doing 70mph, when he had to slam on his brakes to avoid the queue of traffic ahead, and came to a halt a whisker from the car at the end of the queue. Then he thinks to himself......I wonder what would have happened if I, Archie Roberts, in my Passat at 3pm on the M1, had being doing 100 when I slammed on the brakes, instead of 70.
That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph.
Yonex is never going to get it, because to be frank, it's well beyond him, but I was kind of hoping others would. This really is schoolboy physics. You don't need to be Prof Brian Cox to grasp it.
TwigtheWonderkid said:
There is no car A and car B. there's only 1 car, one driver and 1 incident. There is no thinking distance to be considered, because we're talking about events post thinking distance, when you hit the brakes.
I don't know how I can make this any clearer. Archie Roberts was driving his Passat on the M1 yesterday at 3pm, doing 70mph, when he had to slam on his brakes to avoid the queue of traffic ahead, and came to a halt a whisker from the car at the end of the queue. Then he thinks to himself......I wonder what would have happened if I, Archie Roberts, in my Passat at 3pm on the M1, had being doing 100 when I slammed on the brakes, instead of 70.
That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph.
Yonex is never going to get it, because to be frank, it's well beyond him, but I was kind of hoping others would. This really is schoolboy physics. You don't need to be Prof Brian Cox to grasp it.
Let's get a bit more "PH" on this one though, and throw in some unnecessary, unrealistic variables.I don't know how I can make this any clearer. Archie Roberts was driving his Passat on the M1 yesterday at 3pm, doing 70mph, when he had to slam on his brakes to avoid the queue of traffic ahead, and came to a halt a whisker from the car at the end of the queue. Then he thinks to himself......I wonder what would have happened if I, Archie Roberts, in my Passat at 3pm on the M1, had being doing 100 when I slammed on the brakes, instead of 70.
That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph.
Yonex is never going to get it, because to be frank, it's well beyond him, but I was kind of hoping others would. This really is schoolboy physics. You don't need to be Prof Brian Cox to grasp it.
What if Archie Roberts had fitted his Passat with a parachute that only deploys when he slams the brakes on at speeds greater than 99mph?
vonhosen said:
If you are comparing the effects of initial speed it makes sense to do that where the other factors are consistent, then the effects of initial speed (alone) are consistent across the board for everybody.
ie whatever vehicle you're personally driving, in whatever conditions, with whatever reaction time you are going to be carrying a higher residual speed than you probably appreciated at the point where you'd have stopped had you been travelling at a slower initial speed (in those conditions with that reaction time).
That's in practice, not theory.
Then it's not relative to me or anyone else, it's solely about the effects for you with varying initial speeds you are carrying.
IN PRACTICE, you are almost certainly going to be doing a broadly similar speed (+/- 5-10mph) than the car in front in the sort of give-and-take traffic that is most likely to require an emergency stop vis-a-vis 'the car in front', which is where this exchange started. Very few people on a M-way or trunk road barrel-along at 20-30mph more than the surrounding traffic, IF there is traffic. ie whatever vehicle you're personally driving, in whatever conditions, with whatever reaction time you are going to be carrying a higher residual speed than you probably appreciated at the point where you'd have stopped had you been travelling at a slower initial speed (in those conditions with that reaction time).
That's in practice, not theory.
Then it's not relative to me or anyone else, it's solely about the effects for you with varying initial speeds you are carrying.
And if they're blind enough not to spot cars up ahead going slower, then, braking distance or not, the issue is observation as much as it is excess speed. Oh, and planning too. Those two things which are critical to safe driving but we don't actively teach drivers in this country!
Other circumstances are also those which require observation and planning above all else - people joining from side-roads, unexpected hazards, sudden braking for a turn without indicating etc.
...and in those circumstances surely it's more important to have a driver educated to be able to 'read the road' and plan ahead, than someone who's more interested in making sure they're obeying the (arbitrary) limit?!?
SMIDSY is a bigger cause of accidents than excess speed (as per those old police statistics which rounded everything together to get to the "one third" lie - not sure what it's going to be now, but suspect worse still after 20+ years of 'speed kills' and one-dimensional enforcement...not to mention many-more distrations in the car). But SMIDSY is difficult to police, so it doesn't get policed.
(...and then we get more and more draconian mobile phone laws, which are all well and good but are bugger all use if there are no coppers out there TO police them...no good waving a bigger and bigger stick if you're never around to use it...)
So...remind me...exactly WHY were we worrying about braking distances again?!?
TwigtheWonderkid said:
Archie Roberts was driving his Passat on the M1 yesterday at 3pm, doing 70mph, when he had to slam on his brakes to avoid the queue of traffic ahead, and came to a halt a whisker from the car at the end of the queue. Then he thinks to himself......I wonder what would have happened if I, Archie Roberts, in my Passat at 3pm on the M1, had being doing 100 when I slammed on the brakes, instead of 70.
That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph..
- What if Archie had been looking and planning ahead rather than just blindly at the car in front? (or worse, his mobile phone in his lap)That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph..
- What if Archie had (rather more sensibly than your artficial example) left a bigger gap to the car in front?
- What if the cars in front weren't all braking at the limit because they too had all been utter muppets who'd left too short a gap to the car in front that they were myopically focused on.
...and please note that the worst pile-ups on our roads aren't caused by speeding drivers, they're caused by distracted drivers who don't even go for the brake pedal until the last second.
Your example is typical of academics (BTW I have a BSc and a post-grad qualification) - entirely correct on paper but entirely irrelevant in the real world. And which lead to focusing on easily-measurable components rather than the more human variables (training, experience, observation, planning) which in the real world make ALL the difference.
havoc said:
TwigtheWonderkid said:
Archie Roberts was driving his Passat on the M1 yesterday at 3pm, doing 70mph, when he had to slam on his brakes to avoid the queue of traffic ahead, and came to a halt a whisker from the car at the end of the queue. Then he thinks to himself......I wonder what would have happened if I, Archie Roberts, in my Passat at 3pm on the M1, had being doing 100 when I slammed on the brakes, instead of 70.
That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph..
- What if Archie had been looking and planning ahead rather than just blindly at the car in front? (or worse, his mobile phone in his lap)That's the question, and the answer is...Archie would have hit the car at the back of the queue at 71 mph..
- What if Archie had (rather more sensibly than your artficial example) left a bigger gap to the car in front?
- What if the cars in front weren't all braking at the limit because they too had all been utter muppets who'd left too short a gap to the car in front that they were myopically focused on.
...and please note that the worst pile-ups on our roads aren't caused by speeding drivers, they're caused by distracted drivers who don't even go for the brake pedal until the last second.
Your example is typical of academics (BTW I have a BSc and a post-grad qualification) - entirely correct on paper but entirely irrelevant in the real world. And which lead to focusing on easily-measurable components rather than the more human variables (training, experience, observation, planning) which in the real world make ALL the difference.
but then he would have caused that accident primarily doe to stupidity and lack of observation as the primary causes not speed - i.e. his inappropriate speed would have been the consequence of his stupidity / lack of observation...
if on the other hand he allowed 2x - 3x the space at 100mph than the space in your 70mph scenario, he would have no issue in stopping in time - for many drivers, as speed increases so does their feeling of risk and therefore the contingency - others simply get it wrong
these discussions are always a bit silly as the 'theory posited without context' has no real relevance - real life has a much richer set of attributes to consider.
let's consider - empty motorway, I am sure we would all agree that legality / car condition / weather / etc. aside - to drive at 100mph may well be safe.
therefore - a mile ahead is empty - is it safe to go temporarily from 70mph to 100mph for a few hundred years - and then back to 70mph - logically yes
so it is not the speed that is not safe - it is how it is used - the vast majority of cars I have seen doing fast speeds on the motorway do so contextually and with dynamics - i.e. they don't just sit at 90 / 100 regardless of the context - but use empty space for higher speeds, and then back off when approaching traffic - logically that is no less safe than constantly doing 70mph and it means that our fictional Mr Roberts can happily do 100mph, but as he sees traffic building he drops back to 70 or 50 or 30 and all are happy!
yes, sometimes there are drivers who sit at 100mph regardless of the traffic / context - they are idiots, but that doesn't mean that all who do 100mph at some point / for some of their journey are the same...
vonhosen said:
In practice people also tend to over estimate the distance they need available to stop within at low speeds, but under estimate it at high speeds.
Interestingly - taking my (2001) z3 to Bruntingthorpe - I was impressed at how much quicker it stopped down from 50 / 70 / 90 / 110 / etc. than I expected - cars are pretty competent...havoc said:
Your example is typical of academics (BTW I have a BSc and a post-grad qualification) - entirely correct on paper but entirely irrelevant in the real world.
It's relevant in demonstrating that and increase of 30mph from 70 to 100 in initial speed at a given results in a much bigger increase in terminal speed at a given point. And that's all I was attempting to point out. Because most people don't know that. However, it is heartening to see that as a BSc with post grad qualifications, you agree that I'm entirely correct. Maybe we'll both be re-educated when Yonex gets around to posting his alternative kinetic energy formula, having stated that mine was incorrect.
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