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  1. #1
    Gone Fishin' Ray Bell's Avatar
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    Do you believe it?

    There's a current television ad about braking distances...

    The commentary from the joker walking alongside the cars as they rush towards a truck that's driven across their path includes this gem:

    Advertisement


    "The last five metres is where you wipe off half your speed, so this car hits at 32kmh."

    Now this doesn't make sense to me... they have the brakes on for some distance and they wife off the first 32kmh... then in the next 5m they wipe the remaining 32?

    Anyone accept this?

  2. #2
    Fellow Frogger! MR604's Avatar
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    I thought the ad was a community service anouncement on how bad foulcans brakes are. roll_lau roll_lau

    cheers!
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  3. #3
    Good Sport danielsydney's Avatar
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    I think the ad is a waste of time.. 2_cents

  4. #4
    who? when? huh? GTI124's Avatar
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    I think it's a great ad. Overly simplistic, but quite well done. You do lose the majority of your speed in the final few metres.

    I don't like such research being used to promote blatant revenue raising, but if it goes some people thinking about their speed and their surroundings, it's a good thing. 2_cents
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  5. #5
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    I think it's a great ad too Ray. It's certainly made me think... especially when you hear it again on the radio whilst driving around.

    It's simplistic, but then it has to be to cater for the masses. After hearing that you lose most of your speed in the final few metres, I have monitored (or attempted to) the apparent speed I'm doing as I brake and slow down and it does appear that the final few metres do wipe off a huge proportion of the actual speed you're doing.

    Derek.

  6. #6
    Sense Pug307's Avatar
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    I'm sure an engineer could work it out, but braking distance increases exponetially with speed.

    Here are some froggy examples, the Peugeot 206 1.6, courtesy of Autocar.

    30-0 mph - 9.9m (roughly 50-0km/h)
    50-0 mph - 27.5m (roughly 80-0km/h)
    70-0 mph - 54.3m (roughly 110-0km/h)

    As this shows, increasing your speed by 40%, increases stopping distance by over 97% (50-0 mph vs 70-0 mph)

    Also bear in mind the distance covered during reaction time is significant - at 100km/h, you cover almost 28m in a second - that's basically driving past 7 306s all lined up together in a flash.

    One thing that surprised me on a driving course is the effect of speed. You can compensate for it by increasing following distance.

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  7. #7
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    Pug307:
    One thing that surprised me on a driving course is the effect of speed. You can compensate for it by increasing following distance.
    Sure can. If there's one thing that scares me being in a car with someone else driving is being too close to other traffic <img src="http://www.joshuapettit.com/graemlinlibrary/stupid.gif" alt=" - " />

    Thanks for the info about braking distance PUG307 - it appears they are correct in the ad then.

    Derek (this one belongs to mistareno) <img src="http://www.joshuapettit.com/graemlinlibrary/busted.gif" alt=" - " />

  8. #8
    Sense Pug307's Avatar
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    DeKa:
    Derek (this one belongs to mistareno) <img src="http://www.joshuapettit.com/graemlinlibrary/busted.gif" alt=" - " />
    <img src="http://www.hoo-la.com/webmasters/emoticons3d/smil/policier.gif" alt=" - " />

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  9. #9
    1000+ Posts Rod Hagen's Avatar
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    Ray Bell:
    There's a current television ad about braking distances...

    The commentary from the joker walking alongside the cars as they rush towards a truck that's driven across their path includes this gem:

    "The last five metres is where you wipe off half your speed, so this car hits at 32kmh."

    Now this doesn't make sense to me... they have the brakes on for some distance and they wife off the first 32kmh... then in the next 5m they wipe the remaining 32?

    Anyone accept this?
    Go back to some basic physical principles, Ray.

    Basically brakes are devices that convert kinetic energy to heat.

    The kinetic energy of an object is determined by the following formula

    Kinetic Energy = (1/2)*(mass)*(velocity)^2

    Notice that the velocity in this equation is squared.

    If , for example, the velocity of one vehicle is 60 kph and of a second is 65kph then

    KE of the first = 1/2mass x 3600
    KE of the second = 1/2mass x 4225

    When the first vehicle is stopped the brakes will have disposed of all of the klinetic energy of the first vehicle

    For the second vehicle , however, there will still be 1/2mass x 625 to get rid of.

    Going back to our original equation Kinetic Energy = (1/2)*(mass)*(velocity)^2

    We can substitute velocity squared for this remaining 625

    Therefore velocity, by our formula = the square root of 625

    The square root of 625 is 25 and the units we are talking here are kph.

    We would therefore expect the second vehicle to be still travelling at 25 kph when the first one had stopped completely if the vehicles and their braking performance was identical, and they started braking at exactly the same point on the road, simply as a result of the application of basic laws of the physics of moving objects

    But of course, there are other factors that come into play that make the situation even worse for the second, faster travelling, car.

    Firstly there is the question of reaction time. If both drivers have identical reaction time the car travelling at 65kph will have travelled 13/12 the distance of the slower one before the brakes actually come into operation. You can work out the implications of this in terms of kinetic energy and consequent travel speed too, but I can't be bothered right now.

    Secondly there is the question of braking efficiency. This decreases as the brakes heat up. Again the faster car fares worse.

    Looked at from this perspective the 32kph looks pretty reasonable to me.

    Cheers

    Rod

    <small>[ 02 September 2003, 11:49 PM: Message edited by: Rod Hagen ]</small>
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  10. #10
    Gone Fishin' Ray Bell's Avatar
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    Interesting... I wouldn't have expected that.

    Of course, it all looks so different from the driver's seat. You're not working in proportions or calculating time spent moving the foot to the pedal, you're just getting the thing stopped!

  11. #11
    1000+ Posts Rod Hagen's Avatar
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    DeKa:
    If there's one thing that scares me being in a car with someone else driving is being too close to other traffic
    And, unfortunately, nine times out of ten the vehicle behind you will also be driving too close to your own tail as well.

    Very, very few drivers keep adequate separation these days. If you took the average "tailing distance" and doubled or trebled it you'd get closer to the correct separation.

    The even crazier thing about this is that the whole tailgating process actually slows the overall flow of traffic down. There have been some lovely studies done looking at its effect on traffic flow. The "bunching" caused by it, creates repeated "stop start" and "slow down" situations that increase overall travel times substantially (and also increase fuel consumption, pollution levels, brake wear, etc etc) .

    Maybe we need a "double your distance" campaign after "wipe off five". In fact, if everybody did "double their distance" there would be far less need for "wipe off five" on many roads. Trouble is, given the self important impatience of so many drivers, it would be a much harder message to sell to most people.

    Cheers

    Rod

    <small>[ 03 September 2003, 01:07 PM: Message edited by: Rod Hagen ]</small>
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  12. #12
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    Firstly, the road toll is a tragidy whether it be 1 or 1,000,000.

    However, I cannot take any of the ads seriously not because of the reality of the ads but because the government is simply not that serious about reducing the road toll.

    The ad in question as stated above is quite "reasonable" in very very general terms. However, it fails to point out many variables and assumes many things. Most of which are covered above also.

    If the government was really serious. Then they would require all drivers to have refreshers. Learner drivers to satisfactory pass defensive driver courses which SHOULD be at least partially subsidised by them. ALL vehicles be examined for roadworthyness even at 6mnth intervals. Improve roads, etc etc

    Why isn't this happening $$$$. It's easier and more more benfecial to stick up a speed camera and saying they're doing their bit in helping reduce the road toll. Does this REALLY change peoples speeding/driving habits not really. The government needs the money from fines they even have quotas. The amount of revenue raised that goes back into roads is a joke as well.

    Unfortunately, you can't stop some of the idiots out there. Some people don't derserve a licence including many instructors.

    Sorry for the long post but it does anger me when these type of ads come out when so much more could be done if only they spent the dollars the right way.

  13. #13
    who? when? huh? GTI124's Avatar
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    Spending dollars? They're not spending dollars, they're making dollars! This ad is a regurged ad from Victoria. They bought it. So not much spent there.

    Next to nothing is spent on policies that actually reduce the road toll and do not raise revenue at the same time.
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  14. #14
    1000+ Posts Rod Hagen's Avatar
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    GTI124:
    Spending dollars? They're not spending dollars, they're making dollars! This ad is a regurged ad from Victoria. They bought it. So not much spent there.

    Next to nothing is spent on policies that actually reduce the road toll and do not raise revenue at the same time.
    Maybe, GTI, but the Victorian road toll has actually fallen substantially since the heavy policing and ads like the one under discussion here have come in. Maybe its just good luck or maybe the campaign is working.

    The main thing holding a further decline back seems to be a combination of speeding and alcohol consumption by young men in country areas. Got any ideas how they should target that one?

    Cheers

    Rod

    <small>[ 03 September 2003, 02:38 PM: Message edited by: Rod Hagen ]</small>
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  15. #15
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    That's why I try to keep a 3-second gap with the car in front, not by a "set distance" judged by looking at the car in front. So as speed increases the distance increases as well.

    But what do you do when the car behind tailgates you?

    Generally I get out of the way if I can, if I can't, I speed up (even over speed limit if safe to do so) to increase the gap. I hate being tailgated having had a 4WD ran into me from behind. If this doesn't work, I would have no choice but drive at speed limit and let him tailgate...

  16. #16
    1000+ Posts Rod Hagen's Avatar
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    rc968:


    But what do you do when the car behind tailgates you?
    THe "correct" answer to this one, rc, is to slow down sufficiently to add to the normal proper seperation at least the distance between you and the car in front of you that the tailgater should be behind you . In other words, slow down enough to at least double the normal "proper" distance between you and the car in front of you.

    Gravel patches and rear fog lights do become very tempting in these situations though , don't they! No Rod! You mustn't! mallet mallet mallet

    Cheers

    Rod

    <small>[ 03 September 2003, 04:44 PM: Message edited by: Rod Hagen ]</small>
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  17. #17
    Cal
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    Rod Hagen:
    The main thing holding a further decline back seems to be a combination of speeding and alcohol consumption by young men in country areas. Got any ideas how they should target that one?

    Cheers

    Rod
    Hopefully for the rest of us, these are mainly solo vehicle accidents. If so, that is just natural selection, the way it was ment to be.

    Cal.
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  18. #18
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    Rod Hagen:

    Gravel patches and rear fog lights do become very tempting in these situations though , don't they! No Rod! You mustn't!
    evil Heh...at one stage I wanted a rear spot light...

  19. #19
    1000+ Posts Rod Hagen's Avatar
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    Cal:
    Rod Hagen:
    The main thing holding a further decline back seems to be a combination of speeding and alcohol consumption by young men in country areas. Got any ideas how they should target that one?

    Cheers

    Rod
    Hopefully for the rest of us, these are mainly solo vehicle accidents. If so, that is just natural selection, the way it was ment to be.

    Cal.
    Some are, some aren't Cal. And sometimes, of course, even when they are, the car is full of other young people who don't have any real choice in the matter, or are too young to know better and never get the chance to do so. Its pretty desperately sad stuff, not just for the driver or the kids, but for the families that get destroyed in their wake. So. Any answers?

    Cheers

    Rod

    <small>[ 03 September 2003, 05:30 PM: Message edited by: Rod Hagen ]</small>
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  20. #20
    1000+ Posts BogMaster's Avatar
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    Cal:
    Rod Hagen:
    The main thing holding a further decline back seems to be a combination of speeding and alcohol consumption by young men in country areas. Got any ideas how they should target that one?

    Cheers

    Rod
    Hopefully for the rest of us, these are mainly solo vehicle accidents. If so, that is just natural selection, the way it was ment to be.

    Cal.
    Nah Cal,

    it isn't anything other than a tragedy for the victims, their families and the community they live in. Sometimes those kind of accidents can be prevented, but aren't.

    In one town I lived in, the mates of one young bloke at the local lifted him drunk onto his Harley and started it for him so he could ride the 20km along the Snowy Mountains Highway to home. They cheered him off from the footpath. He was dead 15 minutes later. They should have been charged with manslaughter in my book.

    The sad part about country towns is that there are so many pointless deaths of young men through suicide and risk taking behaviour like driving drunk. Every one of the country towns I have lived in has had a litany of this kind of tragedy.

    It's preventable.

    2_cents
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  21. #21
    1000+ Posts Rod Hagen's Avatar
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    The answer to this sort of stuff, if there is one, is going to involve breaking down the mindset that says things like "speed doesn't matter" and "I'm a bloke, I can hack it" or "I've got better skills than the rest of the dingbats out there, so I can break the rules. They aren't really there for people like me."

    Of course in reality its "people like" him, who make up a vastly disproportionate number of the statistics.

    This all to easily gets extended into "I'm a bloke, look at me , I can hack it at 150kph even when I'm drunk, not like those other wusses" (which often , of course, really translates into "I'm really so worthless that the only way I can show em all is to do really dumb things like this")

    Then of course there are the "eggers on". "What are yer. A pansy? My Ford (or Holden or Peugeot or Renault or Citroen) can do a hundred and fifty round that bend! Go on! Give it a go. Give him another tinny!"

    Don't know whether many people here know what its like to lose a kid. I've lost one. She was just a bub and it had nothing to do with cars, but it had a huge effect on my life. Despite this I find it almost unimaginable what it would be like to lose a teenager or a young adult child, even if they "brought it on themselves".

    That's why this stuff matters more than putting up with speed limits.

    Cheers

    Rod
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  22. #22
    1000+ Posts Rod Hagen's Avatar
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    For an even more dramatic example of the consequences of different speeds think back to other day when someone was saying that 140 wasn't that different from 100kph when it came to certain activities.

    Ignoring things like "reaction distance" and brake temperatures completely, apply the basic kinetic energy equation to two identical vehicles, one of which is doing 100kph and the other of which is doing 140.

    If you do, you'll find that ,in this "best case" scenario with both cars performing at maximum braking efficiency, at the time when the vehicle doing 100kph has come to a complete stop the vehicle which was travelling at 140kph will still be doing 98 kph! Who said speed doesn't matter?

    Cheers

    Rod

    <small>[ 03 September 2003, 08:54 PM: Message edited by: Rod Hagen ]</small>
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  23. #23
    1000+ Posts CHRI'S16's Avatar
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    A quick pitch in, most off us here are sensible enough to talk/write about the add and were its acurate or isn't.
    But the average driver, who is not as keen about cars as us, looks at this add and is generaly going to think 3 things.

    A) Its more goverment rubbish.
    or
    B) I don't speed it dosn't affect me. or
    C) Not bother taking in the mesage and think, thats some wicked special effects-

    Taking some of these folks on a trip around some wrecking yards AND better hands on education and driver training would do more to improve driving habits. Either that or they can just give me a free Maserati and ill shut up...lol - chris
    ... ptui!

  24. #24
    Gone Fishin' Ray Bell's Avatar
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    Originally posted by rc968
    <strong>.....But what do you do when the car behind tailgates you?

    Generally I get out of the way if I can, if I can't, I speed up (even over speed limit if safe to do so) to increase the gap. I hate being tailgated having had a 4WD ran into me from behind. If this doesn't work, I would have no choice but drive at speed limit and let him tailgate...
    Frankly, what you are doing is the wrong thing. They have to look after themselves, if you start driving for the guy behind you, you'll be starting to forget driving for yourself. Your attention will be divided...

    Once you know they're there and staying there, just forget about watching them, you've got a car of your own to drive.

  25. #25
    Cal
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    There are two very different arguments going on here. One is about speeding and the other is about drink driving. Sure, sometimes the two combine themselves in a very dangerous cocktail. However, they are essentially different issues.

    I have never had a problem with advertisements directed towards drink drivers. The "every k over is a killer" crap is different.

    I can't help thinking that the reason there are more drink driving fatalities in rural areas are two fold. 1) the distance people need to travel to the pub, dance, party, BBQ whatever is far greater. Transport options are more limited. Young people in the city, would just catch at taxi if they are going to drink. This option may not be viable for country folk. 2) the chances of being caught are vastly lower than in a city.

    I'm no saint and am certain there would be times in my life when my blood alcohol content when driving would have been greater than .05. However, I would never consider driving a vehicle when hammered. Never have. I would be willing to bet that a lot of the young people killed in a drink driving accidents in rural areas have a reading of .1 or far greater.

    There is no answer. Young people are always going to do stupid things. They are also always going to die as a result of those actions. I guess that is what I ment by my rather harsh comment earlier. It is a lot better that it used to be though. Drink driving is hardly socially exceptable behavior, as it was in my father's youth.

    As for the original topic, the ad. More money making propaganda. We keep getting sold this crap about people suddenly appearing in front of the car. Seriously, has anyone here ever had a random pedestrian suddenly turn up in the middle of the road ahead?

    Cheers,

    Cal.

    <small>[ 04 September 2003, 10:29 AM: Message edited by: Cal ]</small>
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