Favourite car advert
Discussion
Kiwi XTR2 said:
Just seen a new (?) RAV4 advert with an exploding house & other miscellaneous chaos
Yeah seen it twice now, very funny indeed
Cant say I have wanted to kill the other half that bad to drive a car. However, the only time we both made a fuss in public was when I bought a brand new Audi home as a replacement car for the night. There was a bit of WWF wrestling going on to get to the drivers seat for a late outing to the shops. The neighbours think we are completely mad...am sure of it.
jamieheasman said:
What about that sad bint banging-on about her Celica GT4? It makes me cringe every time I see it.
When it's on next time, check out the rest of the family - they can probably trace back their heritage for generations without the introduction of a single new gene!
hey come on, she's from Timaru.
Esprit said:
BUT BUT BUT BUT "It's got the beginnings of an anti-lag system" .......
That's the one, oh lordy lord! Clutch sticking a wee bit perhaps? There are / have been some other terrible car adverts - basically any with people singing in their cars (Suzuki Vitara or something, is it?). >> Edited by Murdock on Friday 3rd March 23:11
htsd said:
The one with the dude wakeboarding behind an A6 4.2 V8 was pretty spectacular. They wrote off three A6's doing it (they got crushed back in Germany!!) but I think it has to be one of the best car ads ever made.
Really! is this a new add too, must watch more telly to see this. What channels?
Kiwi XTR2 said:
Just seen a new (?) RAV4 advert with an exploding house & other miscellaneous chaos
After watching the morning show on tele today, its been canned cause 17 people complained it were too offensive and could cause violence in the house
We have two decent cupboards above the fridge and oven that could fit a bowling ball 
The most offensive car ad is the LTSA cars falling from one story = 90kph and 120 = 6 stories.
The bottom feeders have a "Explanation" on the LTSA site which actually shows they are lieing through their teeth. LTSA won't talk to me now as I've pointed out the mistakes and became irate at getting "it's for your own good deary" and Harry Dunhoven has bought the same line from LTSA.
And they bannned the Toyota RAV ad? Idiots.
The small car, evil tow truck ones clever just didn't need to see it 6 times in one night
Cheers
Mark Stacey
The bottom feeders have a "Explanation" on the LTSA site which actually shows they are lieing through their teeth. LTSA won't talk to me now as I've pointed out the mistakes and became irate at getting "it's for your own good deary" and Harry Dunhoven has bought the same line from LTSA.
And they bannned the Toyota RAV ad? Idiots.
The small car, evil tow truck ones clever just didn't need to see it 6 times in one night
Cheers
Mark Stacey
Marksteamnz said:
The most offensive car ad is the LTSA cars falling from one story = 90kph and 120 = 6 stories.
The bottom feeders have a "Explanation" on the LTSA site which actually shows they are lieing through their teeth. LTSA won't talk to me now as I've pointed out the mistakes and became irate at getting "it's for your own good deary" and Harry Dunhoven has bought the same line from LTSA.
And they bannned the Toyota RAV ad? Idiots.
The small car, evil tow truck ones clever just didn't need to see it 6 times in one night
Cheers
Mark Stacey
Exactly Mark (welcome in by the way
) I actually complained to the ASA about the LTSA one they had a year ago where the two identical Falcons, one doing 60km/h, one doing 65km/h both hit the truck. I complained because the different nature of where they "chose" to have the cars hit the truck greatly amplified the "effect" of the crash. I also included a full set of kinematic equations to show that the reaction time of both drivers they used in the commercial was a staggeringly slow 1.7 seconds (an alert, defensive driver should have a reaction time of around 0.5s). 1.7 seconds is the reaction time you might expect to find in someone who is over the limit on blood alcohol. I pointed out to them that they should have a third Falcon, driven by an alert driver doing 76km/h and reacting in a perfectly reasonable 0.7 seconds, he'd have avoided a crash altogether. I basically got the same answer as you... they said hat since it was "in the public interest" the advert was illustrating a point and the advertisers were within their rights to present the advertisment like that..... bloody communist nanny-state bastards!
I always suspected those LTSA adverts sounded dodgy. Have you thought about sending them [Your equations and a brief description of what they mean] away to various newspapers, radio stations (like National Radio for instance which will broadcast nearly anything) and the shadow minister for transport & road safety? I’d be interested in a copy myself actually
A carefully crafted Official Information Request might be able to obtain documentation that would show whether they:
1) Failed to do the physics / maths and just plucked figures from mid-air; or
2) Did the calcs but got them wrong; or
3) Did the calcs, got them right, but decided to mislead the public anyway.
Having been involved in this kind of thing before it is often the specificity of the sin (of commission or omission) that becomes harder to wriggle out of.
And before starting the OI Request process it is often quicker to start with:
"My niece is doing a 7th Form Physics project and would like to study road safety and the impacts of traffic accidents . . ."
1) Failed to do the physics / maths and just plucked figures from mid-air; or
2) Did the calcs but got them wrong; or
3) Did the calcs, got them right, but decided to mislead the public anyway.
Having been involved in this kind of thing before it is often the specificity of the sin (of commission or omission) that becomes harder to wriggle out of.
And before starting the OI Request process it is often quicker to start with:
"My niece is doing a 7th Form Physics project and would like to study road safety and the impacts of traffic accidents . . ."
It's 3)
www.ltsa.govt.nz/advertising/speed/high-rise-calculations.html
for the calculations
The real numbers are 90kph = 12 stories 125kph = 22 stories
So you are toast if you hit a masive granite rock face head on 90kph OOOPS. A bit of a pointless ad for scaring the peons.
What does LTSA do? they deduct 50kph for the "safety" features in the car cushioning your body and get heights of 90kph = 6 meters 125kph = 23 meters.
And now they just LIE 6 meters = one story and 23meters = 6 stories. The famous elastic building syndrome
HANG ON A MINUTE how come 6 meters is 1 story of a building??? Which was my question.
Responses have been flannel and evasion "Oh we said the first floor" "It's for comparision"
The ad clearly shows the car level with the veranda of the building 1 floor 3 METERS up.
www.ltsa.govt.nz/advertising/speed.html for a video link to the ad to show I'm not halucinating.
Plus the ad shows the evil speeders in a car, but remember LTSA deducted 50kph for the car safety features, so to be correct the ad should show, by LTSA reasoning, the family butt naked leaping from a high diving board 6m (20ft for us old farts) on to a concrete drive.
Anyway I'm getting all angry again so off for my pill from the nurse.
Cheers
Mark Stacey
www.ltsa.govt.nz/advertising/speed/high-rise-calculations.html
for the calculations
The real numbers are 90kph = 12 stories 125kph = 22 stories
So you are toast if you hit a masive granite rock face head on 90kph OOOPS. A bit of a pointless ad for scaring the peons.
What does LTSA do? they deduct 50kph for the "safety" features in the car cushioning your body and get heights of 90kph = 6 meters 125kph = 23 meters.
And now they just LIE 6 meters = one story and 23meters = 6 stories. The famous elastic building syndrome
HANG ON A MINUTE how come 6 meters is 1 story of a building??? Which was my question.
Responses have been flannel and evasion "Oh we said the first floor" "It's for comparision"
The ad clearly shows the car level with the veranda of the building 1 floor 3 METERS up.
www.ltsa.govt.nz/advertising/speed.html for a video link to the ad to show I'm not halucinating.
Plus the ad shows the evil speeders in a car, but remember LTSA deducted 50kph for the car safety features, so to be correct the ad should show, by LTSA reasoning, the family butt naked leaping from a high diving board 6m (20ft for us old farts) on to a concrete drive.
Anyway I'm getting all angry again so off for my pill from the nurse.
Cheers
Mark Stacey
Back on topic.
The best car ad was the Barry Crump Toyota one where Scotty took Barry for a strop round Wellington? in retaliation and scared the pants of Barry. It screened for about 3 days? before the hand wringers had it pulled for undermining civilisation and causing the end of the world as we know it.
I'd love to see it again anyone have a copy of it?
Cheers
Mark Stacey
The best car ad was the Barry Crump Toyota one where Scotty took Barry for a strop round Wellington? in retaliation and scared the pants of Barry. It screened for about 3 days? before the hand wringers had it pulled for undermining civilisation and causing the end of the world as we know it.
I'd love to see it again anyone have a copy of it?
Cheers
Mark Stacey
Graham. For the Falcon impacting truck ad, it's actually a very simple set of equations. Although the ad is very brief, they actually give you enough information in the advert to do some rudimentary (but entirely accurate) kinematic comparisons.
My complaint letter originally left this out, concentrating on the obvious bias of the advert's collision. I reprint it for you below.
But if we delve deper into this, we can bring up an even further bias in the "physics" used.
To quote the press release (the video isn't available any more)
This gives us ALL the information we need. But first we must make some assumptions based on the information they state and show in the ad:
* 1. The two cars are identical in every way as well as the conditions each car is under. Tyres, drivers (reaction times), brakes, road surface and condition.
* 2. That both cars decelerate linearly. That is to assume that the driver holds the car at a constant braking force or, as in the case of the two cas in question, the driver brakes as hard as possible meaning that deceleration is completely linear and is dictated by the weight of the car, the friction generated by the tyres and the limits of the ABS system fitted to both test cars. This of course negates brake fade, changes in the road surface etc. but given that neither of these are present or significant under such a situation, these can be ignored. In real world terms, a car operating normally, with constant brake pressure will closely approximate linear deceleration.
* 3. That both drivers hit the brakes (begin decelerating) at the same time and are side by side (as shown in the ad) when they do so 45m away from the point of impact.
Now, this is where I have to start using maths. I've written it all out below but given that there's no code in this forum for superscript and subscript, it doesn't make it easy to follow... so I've hosted a word document that shows all my working and my conclusion with the proper scripture if you can't follow what's going on here.
www.jsr.com/~dinks/Misc/George/LTSA%20Calcs.doc
Enjoy
Now, let’s define some things
Subscripts for the 60km/h car=60, for the 65km/h car=65, i=initial and f=final
v = velocity
a = acceleration
d = displacement (distance) traveled.
Kinematics lays out the equation : vf2 = vi2 + 2ad
This can be rearranged to make a the subject : a = (vf2 – vi2)/2d.
Given that we KNOW that the 60km/h car is initially doing 60km/h (v60 i) and is finally doing 5km/h (v60 f) instantaneously before the point of impact with the truck 45m (d) away. Converting these all to SI units we get:
v60 i = 16.667m/s
v60 f = 1.389m/s
d = 45m
Plugging these numbers into the above equation to derive a, we get the answer a60 = -3.065 m/s2. That is to say that the 60km/h car is decelerating under brakes at 3.065 m/s2.
Given that both situations are IDENTICAL we can deduce that the 65km/h car is decelerating at that same 3.065 m/s2. Therefore a65 = -3.065m/s2.
Let’s test this situation then to verify their claims that the second car impacts the truck doing 32km/h. We can use the same kinematic equation above to determine this.
vf2 = vi2 + 2ad
Now we can arrange this to make the final velocity the subject of the formula:
vf = √(vi2 + 2ad)
Substituting the values we know (converted into SI units):
v65 i = 18.056m/s
a65 = -3.065m/s2
d = 45m
Then we can determine v65 f, the speed of the faster car at the point of impact. The ad tells us that this is 32km/h. The equation laid out above tells a DIFFERENT story, by my calculations (verified) v65 f = 7.083m/s = 25.499km/h.
So we can deduce that from the blurb above, they are LYING and the ad should be taken as completely false information. But let’s backtrack a minute. In the actual advertisement they show the faster car in an offset impact with the windscreen. This means that d >45m, by the length of the Ford Falcon bonnet (about 1.7m). This would result in an even SLOWER impact speed than the calculated 25.499km/h, certainly not the faster 32km/h as advertised.
Because I refuse to believe that the LTSA and the respectable Monash University would not outright lie to us, I investigated further. The ad itself is worded and shown slightly differently from the blurb above. It seems to elude that the drivers do NOT start braking at the same distance from the truck, rather that they SEE the truck at the same time and then both react. Hence my assumption #3 is null and void and the comparison I did SHOULD give us the wrong answer.
We can then assume that this situation is more “real world” and the drivers detect the truck at exactly the same time. There is a “reaction time (tr)” for each driver. This time will be (should be to be a fair comparison) identical for both the cars. It will be the time taken for each driver to see the truck, react to the truck and move their foot to the brake pedal and begin decelerating the car. It is the time taken between the detection of the truck and when the deceleration period starts. Although the reaction time for both cars will be equal, the 65km/h car will travel further than the 60km/h car by virtue of the fact that it is traveling faster over this period. In fact, the longer that this reaction time takes, the more “favourable bias” it gives towards the slower car.
So let’s look at this again. If we take it to be true that they see and react at EXACTLY the same time, and at this point the cars are EXACTLY side by side (as shown in the ad) then we can re-examine this using kinematics again.
We can use the same equation as before: vf2 = vi2 + 2ad but we must apply it for EACH case separately as this equation only holds true over the distance each car is actually braking for. This is NOT the same for each case as the faster car brakes CLOSER to the truck by virtue that it’s traveling faster (therefore further) during the reaction period.
We can, however, postulate that for each car we can define this “reaction distance” as vitr, That is to say, the speed the car is initially going multiplied by the reaction time since v=d/t. Therefore “d” in our equation above can be determined for each case as d = 45-vitr as we know it’s 45m minus the “reaction distance” in each case.
Now, we know we can rearrange vf2 = vi2 + 2ad into a = (vf2 – vi2)/2d . And we also know (from assumption #2) that the accelerations are equal in each case (a60 = a65).
This then forms the grand equation:
(v60 f2 – v60 i2) / 2d60 = (v65 f2 – v65 i2) / 2d65
Now d60 and d65 are unknowns, but can be expressed as 45-v60 itr and 45-v65 itr respectively. Hence we can substitute these in and get
(v60 f2 – v60 i2) / 2(45-v60 itr) = (v65 f2 – v65 i2) / 2(45-v65 itr)
Multiplying through by 2 and separating out the terms then gives us:
(v60 f2 – v60 i2) / (v65 f2 – v65 i2) = (45-v60 itr) / (45-v65 itr) = 45(1- v60 itr/45) / 45(1- v65 itr/45)
Since we know all the values for the initial and final velocities in both cases the LHS of this equation simplifies to 1.117 and we can cancel out the 45 on the top and bottom of the RHS of the equation to get:
1.117 = (1- v60 itr/45) / (1- v65 itr/45)
and therefore:
1.117(1- v65 itr/45) = (1- v60 itr/45)
hence
1.117- 1.117(v65 itr/45) = 1- v60 itr/45
and multiplying through by 45 gives
50.265 – 1.117v65 itr = 45 - v60 itr
and separating out the terms
50.265 – 45 = - v60 itr + 1.117v65 itr
hence
5.265 = tr(- v60 i + 1.117v65 i)
and therefore
tr = 5.265 / (- v60 i + 1.117v65 i)
Substituting in the known values for v60 i and v65 i we then get the final solution that tells us that the reaction time used in the commercial is tr = 1.503s.
Now, 1.503 seconds seems a long time to react to an obstacle and begin braking doesn’t it? Most publications I’ve found list the “average” reaction time for a driver who is alert and paying proper attention to the road at about 0.7s to see an obstacle, react and begin braking to an obstacle. For objects as large as a truck broadside across the road, this may be substantially quicker. A reaction time of around 1.5s is more akin to what they list for someone who has had a couple of glasses of wine or who is “tuned out” and not paying proper attention to the road.
Now say for example we have a person driving along in a THIRD Ford Falcon, they’re driving in exactly the same conditions as the other two, only they’re ALERT. They see the obstacle at EXACTLY the same time as the others when they’re 45m away. They react in the shorter average “alert” reaction time of 0.7s.
From the equations above we can determine that the acceleration (from either one of the two cars)
a = (vf2 – vi2)/2d = (vf2 – vi2)/2trvi = 5.506m/s2
Now, we have the equation vf2 = vi2 + 2ad which can be rearranged to vi2 = vf2 - 2ad
Which becomes vi2 = vf2 - 2a(45-trvi) when we substitute in our equation for the 45m distance minus the “reaction distance”.
Given that we’re assuming that vf = 0 (that is to say that at the point of impact we expect the vehicle to be stationary, hence pulling up at the point of impact) we can simplify this equation to:
vi2 = - 2a(45-trvi)
This equation is a quadratic in vi so we can substitute in the known values for reaction time and acceleration and rearrange the equation to read:
vi2 + 7.708 vi – 495.54 = 0
Given that a quadratic in this form we can solve a quadratic using the quadratic equation:
x = (-b±√(b2-4ac))/2a where x is the solution (in this case vi) and a, b an c are the quadratic coefficients, in this case being a=1, b=7.708 and c=-495.54.
Plugging these values in gives vi = 18.738 or -26.446. Since we know that vi must be positive we can conclude that vi = 18.738m/s or 67.5km/h.
What does this mean then? Well it means that a THIRD identical Ford Falcon, being driven by an ALERT driver could be doing 67.5km/h and react in time to pull up just short of the truck, avoiding the collision that the other two suffer. While this isn’t significantly greater than the faster 65km/h car, let’s remember that even the slower 60km/h car still hits the truck, still doing 5km/h causing minor damage. Our hypothetical third car doing 67.5km/h pulls up with no collision at all. If we were to allow our 67.5km/h car to have a “minor” collision at 5km/h just as we allowed the 60km/h car then the 67.5km/h car would b able to travel even faster, probably around the 73-75km/h mark (I could work this out but can’t be bothered).
So what does this tell us? It tells us first that the LTSA is being very misleading in showing the two natures of accident being different. If the faster car had hit the truck in the same manner as the first car (bumper impact) then although the crash would have still been at 35km/h, the effect would not have been NEARLY as dramatic as what they show on TV with a windscreen-impact.
Secondly it tells us that they’ve used a longer than expected reaction time than you’d expect for an alert and defensive driver. More in line with what you’d expect with a distracted, tired or mildly intoxicated driver. This longer reaction time biases this particular situation in favour of the slower car. What my proof has shown, though, is that above the “speeding kills everyone” message they love to push down our throat, the REAL message we should be able to demonstrate from this advert is that if you’re alert and defensive behind the wheel, a few extra km/h is actually safer than driving slower and less-attentively.
Ladies and gentlemen of the jury, I hereby rest my case.
[/anorak]
>> Edited by Esprit on Sunday 14th May 09:12
My complaint letter originally left this out, concentrating on the obvious bias of the advert's collision. I reprint it for you below.
My Letter said:
The Secretary,
Advertising Standards Complaints Board,
PO Box 10-675,
Wellington.
Dear Sir/Madam,
I am writing to register a complaint about an advertisement for the Land Transport Safety Authority’s anti-speeding campaign shown on Hawkes Bay (or nationwide) television on Channel One at approximately 10:40pm on Monday, 3rd January 2005. The advertisement depicts two identical cars (Ford Falcons) impacting a truck trailer at different speeds.
My objection to this advertisement stems from the fact that this is presented to the viewer with the intent to show the increasing severity of impact at increasing impact velocities. It is my view that the advertisement is portrayed to the viewer as scientific fact when, in fact, the “results” shown in the advertisement are heavily biased. From your own publication on defining the difference between an advertorial and an editorial (www.asa.co.nz/adveored.htm), this advertisement appears to be an editorial and as such has a duty to the viewer to provide an unbiased report of the facts.
The advertisement features Dr Ian Johnston of Australia's Monash University Accident Research Centre explaining how an increase of just 5km/h in travel speed can result in an impact speed several times greater in a crash. Please visit the following website for the LTSA’s own report on the advertisement:
www.ltsa.govt.nz/media/2004/040405.html
From the above website, the LTSA summarises the intent of the experiment and the conditions under which it took place:
“The ad shows two identical vehicles travelling side by side, one at 60km/h and the other at 65km/h. A truck pulls onto the road 45m away, and both drivers hit the brakes at the same time. The ad then illustrates how the laws of physics dictate that the car travelling at 65km/h before braking will hit the truck still doing 32km/h, while the car travelling at 60km/h will hit the truck at just 5km/h - a difference in impact speed of 27km/h.”
I am not for a moment disputing this statement. I have faith that an organization such as the LTSA would not commission an institution like Monash University Accident Research Centre to provide false test results. I must, however, take exception to the heavily biased nature in which the advertisement chooses to display the results of the two resulting impacts:
• The first car (60km/h initial velocity) impacts the trailer unit approximately halfway along its length. The car is going slowly at this point (the LTSA claim 5km/h) and the bumper gently impacts the side of the trailer, dispersing the impact safely and halting the car with little visible damage to the car or truck.
• The second car (65km/h initial velocity) impacts the trailer unit at the rear of the trailer. The impact velocity is clearly much greater (the LTSA claim 32km/h) and the damage is much more severe. The car noses underneath the high rear-end of the trailer and the impact is taken largely by the top of the bonnet and the A-Pillar of the car. The impact causes significant damage to the car, in particular the passenger cabin as the corner of the trailer has penetrated through the windscreen around the vacant near-side front seat.
My complaint is that if the second car had impacted at the same position along the trailer as the first car did, then the impact would have been much less damaging to the car and its occupants. I am not arguing that this advertisement is wrong in principle in that, clearly, a greater impact velocity will result in a heavier impact. This advertisement however does portray an exaggeration of the consequences due to the differing nature of their collisions. Cars are designed to disperse frontal impacts such as this through their bumpers and into the chassis, not directly into the passenger cabin as the impact of the second car shows.
Since this advertisement is clearly intended to be shown to the public as the result of an independent university research investigation, the public is led to believe that the results shown are as-tested and no bias has been placed on them by either the tester or the advertiser. The advertisement specifically states that the cars are identical and the only difference is their initial velocity. No specific mention is made of the fact that the impacts differ so drastically. As such, the public is left to draw this conclusion for themselves, a point to which the average viewer would be oblivious, given the way the advertisement is presented.
I believe that the LTSA has a duty to perform one of the following actions:
• Modify the advertisement to also include specific mention that the natures of the two impacts are different, resulting in exaggerated damage in the case of the second vehicle compared with the first.
• Modify the advertisement to show a more comparable pair of impacts to better show the direct correlation between increased impact velocity and resultant vehicle damage / occupant injury.
• Remove the advertisement from display and all associated advertising material along with a published explanation on why the advertisement was removed.
I submit this letter to you stating my personal complaint about the advertisement in question. I appreciate your feedback as to whether this complaint is grounds for further investigation or not.
Regards,
George Maddever B.E. (Hons.) (Mech.)
But if we delve deper into this, we can bring up an even further bias in the "physics" used.
To quote the press release (the video isn't available any more)
LTSA SCUM said:
The ad shows two identical vehicles travelling side by side, one at 60km/h and the other at 65km/h. A truck pulls onto the road 45m away, and both drivers hit the brakes at the same time. The ad then illustrates how the laws of physics dictate that the car travelling at 65km/h before braking will hit the truck still doing 32km/h, while the car travelling at 60km/h will hit the truck at just 5km/h - a difference in impact speed of 27km/h.
This gives us ALL the information we need. But first we must make some assumptions based on the information they state and show in the ad:
* 1. The two cars are identical in every way as well as the conditions each car is under. Tyres, drivers (reaction times), brakes, road surface and condition.
* 2. That both cars decelerate linearly. That is to assume that the driver holds the car at a constant braking force or, as in the case of the two cas in question, the driver brakes as hard as possible meaning that deceleration is completely linear and is dictated by the weight of the car, the friction generated by the tyres and the limits of the ABS system fitted to both test cars. This of course negates brake fade, changes in the road surface etc. but given that neither of these are present or significant under such a situation, these can be ignored. In real world terms, a car operating normally, with constant brake pressure will closely approximate linear deceleration.
* 3. That both drivers hit the brakes (begin decelerating) at the same time and are side by side (as shown in the ad) when they do so 45m away from the point of impact.
Now, this is where I have to start using maths. I've written it all out below but given that there's no code in this forum for superscript and subscript, it doesn't make it easy to follow... so I've hosted a word document that shows all my working and my conclusion with the proper scripture if you can't follow what's going on here.
www.jsr.com/~dinks/Misc/George/LTSA%20Calcs.doc
Enjoy
Now, let’s define some things
Subscripts for the 60km/h car=60, for the 65km/h car=65, i=initial and f=final
v = velocity
a = acceleration
d = displacement (distance) traveled.
Kinematics lays out the equation : vf2 = vi2 + 2ad
This can be rearranged to make a the subject : a = (vf2 – vi2)/2d.
Given that we KNOW that the 60km/h car is initially doing 60km/h (v60 i) and is finally doing 5km/h (v60 f) instantaneously before the point of impact with the truck 45m (d) away. Converting these all to SI units we get:
v60 i = 16.667m/s
v60 f = 1.389m/s
d = 45m
Plugging these numbers into the above equation to derive a, we get the answer a60 = -3.065 m/s2. That is to say that the 60km/h car is decelerating under brakes at 3.065 m/s2.
Given that both situations are IDENTICAL we can deduce that the 65km/h car is decelerating at that same 3.065 m/s2. Therefore a65 = -3.065m/s2.
Let’s test this situation then to verify their claims that the second car impacts the truck doing 32km/h. We can use the same kinematic equation above to determine this.
vf2 = vi2 + 2ad
Now we can arrange this to make the final velocity the subject of the formula:
vf = √(vi2 + 2ad)
Substituting the values we know (converted into SI units):
v65 i = 18.056m/s
a65 = -3.065m/s2
d = 45m
Then we can determine v65 f, the speed of the faster car at the point of impact. The ad tells us that this is 32km/h. The equation laid out above tells a DIFFERENT story, by my calculations (verified) v65 f = 7.083m/s = 25.499km/h.
So we can deduce that from the blurb above, they are LYING and the ad should be taken as completely false information. But let’s backtrack a minute. In the actual advertisement they show the faster car in an offset impact with the windscreen. This means that d >45m, by the length of the Ford Falcon bonnet (about 1.7m). This would result in an even SLOWER impact speed than the calculated 25.499km/h, certainly not the faster 32km/h as advertised.
Because I refuse to believe that the LTSA and the respectable Monash University would not outright lie to us, I investigated further. The ad itself is worded and shown slightly differently from the blurb above. It seems to elude that the drivers do NOT start braking at the same distance from the truck, rather that they SEE the truck at the same time and then both react. Hence my assumption #3 is null and void and the comparison I did SHOULD give us the wrong answer.
We can then assume that this situation is more “real world” and the drivers detect the truck at exactly the same time. There is a “reaction time (tr)” for each driver. This time will be (should be to be a fair comparison) identical for both the cars. It will be the time taken for each driver to see the truck, react to the truck and move their foot to the brake pedal and begin decelerating the car. It is the time taken between the detection of the truck and when the deceleration period starts. Although the reaction time for both cars will be equal, the 65km/h car will travel further than the 60km/h car by virtue of the fact that it is traveling faster over this period. In fact, the longer that this reaction time takes, the more “favourable bias” it gives towards the slower car.
So let’s look at this again. If we take it to be true that they see and react at EXACTLY the same time, and at this point the cars are EXACTLY side by side (as shown in the ad) then we can re-examine this using kinematics again.
We can use the same equation as before: vf2 = vi2 + 2ad but we must apply it for EACH case separately as this equation only holds true over the distance each car is actually braking for. This is NOT the same for each case as the faster car brakes CLOSER to the truck by virtue that it’s traveling faster (therefore further) during the reaction period.
We can, however, postulate that for each car we can define this “reaction distance” as vitr, That is to say, the speed the car is initially going multiplied by the reaction time since v=d/t. Therefore “d” in our equation above can be determined for each case as d = 45-vitr as we know it’s 45m minus the “reaction distance” in each case.
Now, we know we can rearrange vf2 = vi2 + 2ad into a = (vf2 – vi2)/2d . And we also know (from assumption #2) that the accelerations are equal in each case (a60 = a65).
This then forms the grand equation:
(v60 f2 – v60 i2) / 2d60 = (v65 f2 – v65 i2) / 2d65
Now d60 and d65 are unknowns, but can be expressed as 45-v60 itr and 45-v65 itr respectively. Hence we can substitute these in and get
(v60 f2 – v60 i2) / 2(45-v60 itr) = (v65 f2 – v65 i2) / 2(45-v65 itr)
Multiplying through by 2 and separating out the terms then gives us:
(v60 f2 – v60 i2) / (v65 f2 – v65 i2) = (45-v60 itr) / (45-v65 itr) = 45(1- v60 itr/45) / 45(1- v65 itr/45)
Since we know all the values for the initial and final velocities in both cases the LHS of this equation simplifies to 1.117 and we can cancel out the 45 on the top and bottom of the RHS of the equation to get:
1.117 = (1- v60 itr/45) / (1- v65 itr/45)
and therefore:
1.117(1- v65 itr/45) = (1- v60 itr/45)
hence
1.117- 1.117(v65 itr/45) = 1- v60 itr/45
and multiplying through by 45 gives
50.265 – 1.117v65 itr = 45 - v60 itr
and separating out the terms
50.265 – 45 = - v60 itr + 1.117v65 itr
hence
5.265 = tr(- v60 i + 1.117v65 i)
and therefore
tr = 5.265 / (- v60 i + 1.117v65 i)
Substituting in the known values for v60 i and v65 i we then get the final solution that tells us that the reaction time used in the commercial is tr = 1.503s.
Now, 1.503 seconds seems a long time to react to an obstacle and begin braking doesn’t it? Most publications I’ve found list the “average” reaction time for a driver who is alert and paying proper attention to the road at about 0.7s to see an obstacle, react and begin braking to an obstacle. For objects as large as a truck broadside across the road, this may be substantially quicker. A reaction time of around 1.5s is more akin to what they list for someone who has had a couple of glasses of wine or who is “tuned out” and not paying proper attention to the road.
Now say for example we have a person driving along in a THIRD Ford Falcon, they’re driving in exactly the same conditions as the other two, only they’re ALERT. They see the obstacle at EXACTLY the same time as the others when they’re 45m away. They react in the shorter average “alert” reaction time of 0.7s.
From the equations above we can determine that the acceleration (from either one of the two cars)
a = (vf2 – vi2)/2d = (vf2 – vi2)/2trvi = 5.506m/s2
Now, we have the equation vf2 = vi2 + 2ad which can be rearranged to vi2 = vf2 - 2ad
Which becomes vi2 = vf2 - 2a(45-trvi) when we substitute in our equation for the 45m distance minus the “reaction distance”.
Given that we’re assuming that vf = 0 (that is to say that at the point of impact we expect the vehicle to be stationary, hence pulling up at the point of impact) we can simplify this equation to:
vi2 = - 2a(45-trvi)
This equation is a quadratic in vi so we can substitute in the known values for reaction time and acceleration and rearrange the equation to read:
vi2 + 7.708 vi – 495.54 = 0
Given that a quadratic in this form we can solve a quadratic using the quadratic equation:
x = (-b±√(b2-4ac))/2a where x is the solution (in this case vi) and a, b an c are the quadratic coefficients, in this case being a=1, b=7.708 and c=-495.54.
Plugging these values in gives vi = 18.738 or -26.446. Since we know that vi must be positive we can conclude that vi = 18.738m/s or 67.5km/h.
What does this mean then? Well it means that a THIRD identical Ford Falcon, being driven by an ALERT driver could be doing 67.5km/h and react in time to pull up just short of the truck, avoiding the collision that the other two suffer. While this isn’t significantly greater than the faster 65km/h car, let’s remember that even the slower 60km/h car still hits the truck, still doing 5km/h causing minor damage. Our hypothetical third car doing 67.5km/h pulls up with no collision at all. If we were to allow our 67.5km/h car to have a “minor” collision at 5km/h just as we allowed the 60km/h car then the 67.5km/h car would b able to travel even faster, probably around the 73-75km/h mark (I could work this out but can’t be bothered).
So what does this tell us? It tells us first that the LTSA is being very misleading in showing the two natures of accident being different. If the faster car had hit the truck in the same manner as the first car (bumper impact) then although the crash would have still been at 35km/h, the effect would not have been NEARLY as dramatic as what they show on TV with a windscreen-impact.
Secondly it tells us that they’ve used a longer than expected reaction time than you’d expect for an alert and defensive driver. More in line with what you’d expect with a distracted, tired or mildly intoxicated driver. This longer reaction time biases this particular situation in favour of the slower car. What my proof has shown, though, is that above the “speeding kills everyone” message they love to push down our throat, the REAL message we should be able to demonstrate from this advert is that if you’re alert and defensive behind the wheel, a few extra km/h is actually safer than driving slower and less-attentively.
Ladies and gentlemen of the jury, I hereby rest my case.
[/anorak]
>> Edited by Esprit on Sunday 14th May 09:12
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