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Thread: Lowering speed limits to 80 (from 100) and 30/40 (from 50)... A research paper.

  1. #91
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    Quote Originally Posted by speedpro View Post
    What happened to the road toll when the speed limit was reduced to 80km/h years ago when imported fuel costs jumped? Supposedly the lower speed was going to result in lower fuel consumption, which I doubt was actually an effect, all to do with thermodynamic efficiencies of engines at various speeds and loads. Another example of being seen to be doing something, like lowering the speed limit, again, now.
    Are there any stats to show the road toll changed during the fuel crisis 80km/h period? That would have been a good demonstration of how changing nothing other than the speed limit works, or doesn't work, wrt road crashes. Once the limit was reinstated to 100, did crash stats show a comparable jump?
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  2. #92
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    Quote Originally Posted by pete376403 View Post
    Are there any stats to show the road toll changed during the fuel crisis 80km/h period? That would have been a good demonstration of how changing nothing other than the speed limit works, or doesn't work, wrt road crashes. Once the limit was reinstated to 100, did crash stats show a comparable jump?
    Here's one of the many clippings I have laying round

    In the early 1970s, as a result of the 1973 oil shock, both New Zealand and the United States imposed new, lower speed limits in an effort to save fuel. In New Zealand?s case the limit dropped from 60 mph (100ks) to 50mph (80ks), while in the US it dropped to 55 mph - the so-called "double nickel".

    In the ten years leading up to the drop in the New Zealand speed limit, an average of 608 New Zealanders had died on the roads each year.
    In the ten years that followed the drop from 100 kph down to 80 kph, an average of 707 New Zealanders died on the roads each year: in other words, the new, lower New Zealand speed limit coincided with a 17% increase in road deaths. Starting to get the picture?
    Then, in 1985, the New Zealand Government decided to raise the speed limit again, from 80kph back up to 100kph. The result?

    Well, admittedly there was a big jump in road deaths that year as people got used to driving their cars faster, but it also coincided with boom times in the economy and a big increase in drink-driving offences.
    However, over the next ten years, the average number of New Zealanders killed on the roads each year was 699, a slight drop when compared with the ten years under a lower speed limit.

    Could it actually be that allowing cars to drive faster decreases the road toll overall? Sure, the chances of surviving a crash at a higher speed were much slimmer for those involved, but perhaps the higher speeds contributed to smoother traffic flows and less road rage.
    One of the reasons that road toll statistics supplied by the old Ministry of Transport, and latterly the LTSA, have been misleading is because the LTSA does not measure "deaths per vehicle kilometre travelled", which is the only true measure of whether the road toll is really going up or down.

    For example, if 1000 people die on the roads each year, during which time the nation?s cars have travelled a million kilometres, the ratio is one death per thousand kilometres. You can then compare that figure to a subsequent year when, perhaps, 1100 people were killed but (because of cheaper petrol maybe) the nation?s cars travelled 1.3 million kilometres.
    The LTSA would simplistically tell the public "the road toll has increased", without realising that the "death per kilometre ratio" has dropped to 1 per 1181 kilometres. The truth in such a situation is that the road toll has dropped in real terms, by about 20 percent.
    The closest New Zealand gets to any worthwhile statistics at all are the figures that measure the ratio of deaths to the number of cars on the road.

    For the ten years that our maximum speed limit was only 80 kilometres per hour, an average of 3.75 New Zealanders were killed each year for every ten thousand cars on the road.

    For the ten years after that, when the speed limit increased to 100 kph, the average number of deaths dropped by 12%, to just 3.27 deaths per 10,000 vehicles.

    The ratio of people injured per 10,000 vehicles tells a similar story: during the low speed era, an average of 100.6 injuries. During the high speed era that followed: just 80.5. A twenty percent drop in injuries in real terms when cars were allowed to travel faster.
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  3. #93
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    Quote Originally Posted by FJRider View Post
    Two vehicles travelling at 80 km/hr ... crash head on into each other. Impact speed of 160 km/hr ...
    Nope it doesn't work like that. Look it up.
    ..................

  4. #94
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    Quote Originally Posted by jasonu View Post
    Nope it doesn't work like that. Look it up.
    That'll make an interesting read. Where should I look? I always thought 80 plus 80 = 160.

  5. #95
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    Double the mass.

    So at the extreme let's say you are a blow fly travelling at 80kph (wow) and you hit a truck. Your potential energy is close to zero.

    A Brick wall has a lot of Mass but velocity of zero. It will do no work on you.(unfortunately it is at rest and to move it you need to accelerate a large mass instantaneously which is doomed to failure).

    Now swap a few of the vehicles around and run them into things at various speeds.
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  6. #96
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    Quote Originally Posted by rastuscat View Post
    That'll make an interesting read. Where should I look? I always thought 80 plus 80 = 160.
    In this case 80 + 80 dosen't make 160.

    Sent from my SM-G965F using Tapatalk
    Quote Originally Posted by Katman View Post
    but once again you proved me wrong.
    Quote Originally Posted by cassina View Post
    I was hit by one such driver while remaining in the view of their mirror.

  7. #97
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    Well it does make 160, . . . but that ignores the energy imparted.
    I've been told. Dreaming`s free.
    Think I'll go, back to sleep.
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    Everybody listen, do yours say, what mine says?

  8. #98
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    Quote Originally Posted by F5 Dave View Post
    Well it does make 160, . . . but that ignores the energy imparted.
    So a Hilux penis extender travelling at 80 hits an equivalent Hilux penis extender also travelling at 80, directly head on.

    Isn't the impact equal on both parts, and equivalent to a Hilux penis extender hitting a solid fixed object at 160?

  9. #99
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    Quote Originally Posted by rastuscat View Post
    So a Hilux penis extender travelling at 80 hits an equivalent Hilux penis extender also travelling at 80, directly head on.

    Isn't the impact equal on both parts, and equivalent to a Hilux penis extender hitting a solid fixed object at 160?
    No, you're penis is hitting at 80kph.

    Still hurt though.

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    Quote Originally Posted by Katman View Post
    but once again you proved me wrong.
    Quote Originally Posted by cassina View Post
    I was hit by one such driver while remaining in the view of their mirror.

  10. #100
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    Quote Originally Posted by rastuscat View Post
    So a Hilux penis extender travelling at 80 hits an equivalent Hilux penis extender also travelling at 80, directly head on.

    Isn't the impact equal on both parts, and equivalent to a Hilux penis extender hitting a solid fixed object at 160?
    Na, it's based on the 2 equal forces cancelling each other out & so each vehicle only takes the impact of their speed
    HOWEVER in the real world things aren't equal so the penis extender at 80km/h hitting a 1990' Toymota Corolla at 80km/h is gonna produce different results for each party (the 'Rolla taking the bigger hit) same way us bikes don't fair too well regardless of speed.
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  11. #101
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    Quote Originally Posted by rastuscat View Post
    That'll make an interesting read. Where should I look? I always thought 80 plus 80 = 160.
    Ask the internet.
    I'm a little surprised an ex popo doesn't know this.
    ..................

  12. #102
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    just wish they'd police mobile phone users while driving etc / be easy on some popo bikes with gopros, the public video and post to youtube all the time why the feck dont the police >_>?

  13. #103
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    Quote Originally Posted by jasonu View Post
    Ask the internet.
    I'm a little surprised an ex popo doesn't know this.
    Speed Kills seems to be the only known thing today. I seen it on the TV

  14. #104
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    Well yes, it's true.

    Stationary objects don't collide.

  15. #105
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    Quote Originally Posted by rastuscat View Post
    So a HPE travelling at 80 hits an equivalent HPE also travelling at 80, directly head on.

    Isn't the impact equal on both parts, and equivalent to a HPE hitting a solid fixed object at 160?
    Nope. A vehicle hitting a solid object at 80 km/h decelerates over whatever time it takes to get through the crumple zone. Replace the solid object with an equal vehicle moving at 80 km/h in the opposite direction. The centre of the colliding vehicles remains stationary, just like the solid object model, so each vehicle again decelerates over the same time as when hitting the solid object. The result is the same forces applied to each vehicle and therefore the occupants.

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