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Speaker: Sponsored post: Speed and Safety

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  • Matthew Poole, in reply to George Darroch,

    We’ve scrubbed off about 5km/h over the last decade, and that has saved a lot of lives.

    Over the last decade the vehicle fleet has got safer and many of the worst roads have been improved. The annual road toll at Pukerua Bay has dwindled to somewhere around zero instead of being around five every year, to name one example. The dividing of SH1 between Hamilton and Auckland has, similarly, reduced the incidence of fatal collisions along that road.

    The insistence that it's the focus on speed which has reduced the road toll is given lie by the incredibly patchy results for year-on-year holiday period road tolls. Sometimes they're up, sometimes they're down, despite the police pushing the 4km/h tolerance. If it was all down to speed, we shouldn't be seeing such huge variation.

    Auckland • Since Mar 2007 • 4097 posts Report Reply

  • Chris Waugh, in reply to Greg Wood,

    8.2 metres is actually quite a long way into another person's car.

    Roughly two car lengths into another person's car?

    Wellington • Since Jan 2007 • 2401 posts Report Reply

  • steven crawford, in reply to George Darroch,

    Tradesmen are the worst.

    We have come a generally long way from the days when it was Women, Asian and or Sunday drivers.

    Atlantis • Since Nov 2006 • 4306 posts Report Reply

  • James Butler, in reply to Matthew Poole,

    Not four times as bad? Or some other even higher number? I’d have thought driving/crashing at 100km/h was much more dangerous than driving/crashing at 50km/h.

    In terms of released energy, yes, it’s four times as bad thanks to the “squared” in the theory of relativity.

    *cough* Not quite - it's all Newtonian. A car's kinetic energy is 1/2(mv^2). So one car hitting a perfectly strong wall at 100km/h will release four times the energy of the same car hitting the same wall at 50 km/h; but two identical cars hitting each other head on at identical speeds will only release twice as much as one hitting a wall at the same speed.

    Think of it this way - in both the car-hits-wall case and the car-hits-car case, each car decelerates from v to zero during the collision, so the total energy is e * (number of cars).

    (Russell - how about LaTeX parsing for comments?)

    Auckland • Since Jan 2009 • 856 posts Report Reply

  • Martin Lambert, in reply to Matthew Poole,

    That extra 15% of energy may well be the reason you die....every tissue in the human body has a breaking point! Whilst everyone's tissue is different, a 15% difference in energy in a motor vehicle impact may be the difference between tissue injury and tissue failure resulting in fatality.

    North Shore • Since Dec 2006 • 6 posts Report Reply

  • James Butler,

    In the relativistic case, the entire mass of the car would be instantly converted to energy at the rate of mc^2, which for a 1.5 tonne car would be an explosion equivalent to several gigatons of TNT. That would be one incentive to drive safely.

    Auckland • Since Jan 2009 • 856 posts Report Reply

  • Rich of Observationz, in reply to Russell Brown,

    And rather different roads, too

    Actually, not so much,

    The UK has no unsealed roads, but a lot of one lane roads, sunken in a ditch and with mud all over the surface

    All three countries have modern motorways, but also many secondary roads just like ours and many urban roads, especially in the US, that are way worse than ours (for instance the Bay Bridge).

    Possibly we have more roads in the "good enough to die on but not good enough to save you" class, but I think being really bad drivers helps. And if all you do is slow people down, we'll have really bad slow drivers.

    Back in Wellington • Since Nov 2006 • 5550 posts Report Reply

  • Matthew Poole, in reply to Greg Wood,

    Let’s take a look at that using physics.

    All else being equal, stopping distance at 100km/h = 49.2m, while stopping distance at 108km/h = 57.4m

    8.2 metres is actually quite a long way into another person’s car.

    Yes, but human reaction times are not instant. The through car is so close to the intersection when the other driver pulls out that it would take a very alert, very quick driver to have done much more than get their foot off the accelerator before impact.
    We're not talking about pulling up short, we're talking about a near-full-speed side-impact collision at speeds that are not survivable until a heck of a lot of momentum has been lost. The ad shows a crash where a driver who was abiding the 100km/h speed limit would still have collided at pretty much their full speed with a driver who just pulled out in front.

    Watch the ad. Pause it at the moment where the car pulls out. The through driver has about a second to react, half a second of braking time if he's doing well. But it's not half a second, because by the time he's got his foot on the brake pedal the distance to impact (check out the aerial shot) is down to about nine metres, or less than 1/3 of a second at 100km/h (27.8m/s at 100km/h, 30m/s at 108km/h). Physics, also, says that maximum braking force is not immediately applied because it takes time to depress the pedal, for the brake fluid to compress and apply the brakes, the friction surfaces to make contact and begin slowing the car...
    The speed is irrelevant. Not even Michael Schumacher could have braked fast enough to stop it being a fatal side impact (ignoring that he'd likely have spotted the crash before it happened and taken early evasive action).

    Auckland • Since Mar 2007 • 4097 posts Report Reply

  • Rich of Observationz, in reply to James Butler,

    You can see why the Ford Nucleon never made it into production?

    Back in Wellington • Since Nov 2006 • 5550 posts Report Reply

  • Ian Dalziel, in reply to Russell Brown,

    I’ve never thought of the CF Bedford
    in quite that way …

    ...to be honest I never thought it in the CF Bedford, that was one solid beast, it was in the later Nissan(?) Vanette - which felt about as safe as an aluminium takeaway container - that those thoughts kept flickering through my mind...

    And technically, I suppose, with all those magazines on board it could've been called a moving 'stationery object' - or is that pushing the envelope?

    :- )

    Christchurch • Since Dec 2006 • 7886 posts Report Reply

  • Brent Jackson, in reply to James Butler,

    but two identical cars hitting each other head on at identical speeds will only release twice as much as one hitting a wall at the same speed.

    And that energy is spread over twice the material (ie 2 cars as opposed to 1), so from a car's occupant's perspective, a head-on collision (with a similar-sized, and speed vehicle) is the same as hitting an immovable object at the same speed.

    Auckland • Since Nov 2006 • 614 posts Report Reply

  • James Butler, in reply to Brent Jackson,

    Quite true.

    Auckland • Since Jan 2009 • 856 posts Report Reply

  • Clarke,

    I've never quite figured out the NZ obsession with speed being classed as the primary killer on the roads, when that's only true in the absolute sense - casualties can only be guaranteed drop to zero only if the speed drops to zero, which rather defeats the purpose of NZTA spending billions and billions and billions on more roads.

    Clearly it's bad judgement that causes crashes, not speed per se, and I agree that the ad would have been more honest if the issue of speed had been left off the table - even at 95km/hr, the crash depicted in the ad would have occurred.

    But we seem to have some sort of cultural issue with attributing most crashes to driver error; even the media is in on it.

    In far too many cases, the news report of an entirely preventable crash has a description like "the car left the road and hit a power pole" ... as though the car had some sort of independent agency, and the driver was a mere uninvolved spectator in the proceedings. It should say, "the driver failed to display suitable skills and drove his/her car into a power pole". It would at least have the benefit of honesty about where the responsibility for the crash lies. If we can routinely attribute plane crashes to pilot error, I don't know why we can't attribute road crashes to driver error.

    But in my view, the focus on speed comes because it makes for easy enforcement. It's easy to measure, the speed limit is objective rather than subjective, and it's amenable to instant fines and very structured prosecutions. Enforcing good judgement is a somewhat more complex and fraught process, but one more likely to produce better long-term results.

    And in that context, it's worth asking the question about why getting a license in a rural area 40 years ago means you're still qualified to drive a car of double the weight and five times the power in busy Auckland motorway traffic, with no evidence of any subsequent re-training. We don't allow surgeons to carry on willy-nilly for four decades without regular refreshers, because they might kill people ... but apparently it's OK to let people in charge of a few tonnes of speeding metal without as much as a casual glance in the direction of the Road Code for that period of time, because it's not like they'd kill people ...

    Wellington • Since Nov 2006 • 85 posts Report Reply

  • Brent Jackson, in reply to Stephen Judd,

    I usually drive dead on 50 kph.

    Is that 50 according to your speedo, or 50 as measured correctly ? Modern car's speedos seem to read about 8% lower than the car's actual speed. This has probably been the main contributor to the lowering of average speeds. However, a lot of that will be people driving at 90 thinking they're driving at 100, instead of people driving over 110 actually slowing down.

    Auckland • Since Nov 2006 • 614 posts Report Reply

  • Stephen Judd, in reply to Brent Jackson,

    Is that 50 according to your speedo, or 50 as measured correctly ?

    I don't know. Those fancy roadside displays that tell you what your speed is and my speedo agree very well, though.

    Wellington • Since Nov 2006 • 3122 posts Report Reply

  • David Hood, in reply to Brent Jackson,

    When a collision takes place the kinetic energy gets divided up among the car/car car/wall in some potentially complicated but important fashion. When a car hits a wall we don't much care what happens to the wall. It is like how much difference the stopping distance makes depends on how far away you are to apply it (so we can argue over what the numbers mean). But I think however much we argue about the numbers in different scenarios we probably all agree more speed equals worse outcome (other things being equal).

    James, there is the old dodge of making an equation into a picture and uploading that.

    Dunedin • Since May 2007 • 1443 posts Report Reply

  • Ian Dalziel, in reply to Rich of Observationz,

    why the Ford Nucleon never made it into production

    Then there is that DeLorean
    Run, DMC, Run...

    Christchurch • Since Dec 2006 • 7886 posts Report Reply

  • Stephen Judd,

    Some interesting race/class things lurking in this video which I don't feel competent to give a close reading of right now.

    Wellington • Since Nov 2006 • 3122 posts Report Reply

  • izogi, in reply to Brent Jackson,

    Modern car’s speedos seem to read about 8% lower than the car’s actual speed.

    I hadn’t realised how widespread this was until I drove around with a SatNav for a few weeks in the UK, and it displayed the actual speed compared with the speed limit for the section of road (which was very useful – totally useless and dangerously misleading once we reached Ireland because everything was out of date).

    Even a GNSS-based speedo will under-read on corners, though, unless there’s some kind of internal algorithm to compensate, though, because if it’s not a perfectly straight line then the points it’s measuring between will be closer than the distance actually driven.

    Wellington • Since Jan 2007 • 1139 posts Report Reply

  • Rich of Observationz, in reply to izogi,

    Not reading high is a functional requirement of various vehicle certification authorities, so speedometers read low by design (as they will always have an error budget).

    Also, some GPS receivers use doppler measurements for speed, which doesn't suffer from sampling artefacts as you turn corners.

    Back in Wellington • Since Nov 2006 • 5550 posts Report Reply

  • Russell Brown, in reply to Clarke,

    In far too many cases, the news report of an entirely preventable crash has a description like “the car left the road and hit a power pole” … as though the car had some sort of independent agency, and the driver was a mere uninvolved spectator in the proceedings. It should say, “the driver failed to display suitable skills and drove his/her car into a power pole”.

    Or … the driver was travelling too fast for the conditions, was unable to control the car and left the road. Perhaps the driver’s skill level was a factor too, or the weather or the state of the road. That seems to be the point here – that while speed in itself may be the sole cause of relatively few crashes, it’s a contributory factor in many more.

    According to the MoT, speed (defined as "driving too fast for the conditions") was a contributory factor in 29% of fatal accidents from 2010-2012 and “the more serious the crash, the more likely it is that speed was a contributing factor.”

    Enforcing good judgement is a somewhat more complex and fraught process, but one more likely to produce better long-term results.

    Like, say, through public advisory campaigns on TV and the internet?

    Auckland • Since Nov 2006 • 22747 posts Report Reply

  • Tom Ackroyd, in reply to Stephen Judd,

    And I'm interested in Rich of Observationz' race/class reading of the Ghost chips ad.

    Are you going to be running one of those “funny” racist ads next with the drunk Māori dude talking in the silly voice?

    Wellington • Since Nov 2006 • 159 posts Report Reply

  • Russell Brown, in reply to Tom Ackroyd,

    And I’m interested in Rich of Observationz’ race/class reading of the Ghost chips ad.

    Are you going to be running one of those “funny” racist ads next with the drunk Māori dude talking in the silly voice?

    I’m completely puzzled by that reading of it, if he was actually talking about "ghost chips". The genius of “ghost chips” was surely that it granted agency and insight to a character who might not be expected to have either and, as as British site Creative Review notes, it “succeeds by not patronising its main audience.” (Which is arguably where the confusing Drive Social campaign falls down.)

    And apart from anything else, the meme jackpot was well and truly struck by that ad. You don’t manage that by insulting your audience or being racist about them. So that just seems like a weird criticism to me.

    Auckland • Since Nov 2006 • 22747 posts Report Reply

  • Jeremy Andrew,

    So, this post is sponsored by the NZTA. Does this mean our speeding tickets are indirectly feeding Russell and his clan?

    Hamiltron - City of the F… • Since Nov 2006 • 900 posts Report Reply

  • Moz, in reply to Jeremy Andrew,

    So, this post is sponsored by the NZTA. Does this mean our speeding tickets are indirectly feeding Russell and his clan?

    I hope so. It would be nice to think that voluntary taxation was going to a good home. ... but let's not get too political.

    One day I hope to get a speeding ticket, but every year I get a little bit slower, so unless I take up speeding on the (rare) 10kph signposted shared paths it's not likely. And the cops are normally uncooperative even when a bike does manage to trigger their radar.

    Sydney, West Island • Since Nov 2006 • 1193 posts Report Reply

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