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80mph speed limit 'would increase deaths by 20%'

(24 posts)

  1. crowriver
    Member

    80mph speed limit 'would increase deaths by 20%'
    Statistical model used by Department for Transport predicts 25 extra motorway deaths a year if plans to increase limit go ahead

    http://www.guardian.co.uk/uk/2011/dec/25/80mph-speed-limit-increase-deaths

    The impact can be even more severe because higher motorway speed limits can spill on to connecting roads, he added: "People tend to adapt to the speed they're travelling. When you have someone exit an interstate highway, for example, we see that they go faster than other people on the roadway. Even if you think you've slowed down, you often haven't slowed down as much as you perceive."

    Posted 13 years ago #

  2. LivM
    Member

    A solution to that we encountered when in India was to have the world's fiercest speedbumps (they were like kerbs, honestly) at the bottom of the slip road off the "motorway" heading into Mumbai from Pune. You literally could not go over them faster than about 5mph. It certainly took the wind out of a lot of sails!

    Posted 13 years ago #

  3. chdot
    Admin

    "Report warns 80mph speed limit is bad for... everything"

    http://www.independent.co.uk/life-style/motoring/motoring-news/report-warns-80mph-speed-limit-is-bad-for-everything-6285643.html

    Posted 13 years ago #

  4. Wilmington's Cow
    Member

    "A solution to that we encountered when in India was to have the world's fiercest speedbumps (they were like kerbs, honestly) at the bottom of the slip road off the "motorway" heading into Mumbai from Pune. You literally could not go over them faster than about 5mph. It certainly took the wind out of a lot of sails!"

    Although speed limits in India are completely... erm... pointless. A bit like traffic lights. And separate lanes. Interesting to be hurtling down a motorway and see trucks coming towards you in your lane.

    Most terrifying experience, however, was being driven to the airport outside Varanasi at breakneck speed, dodging potholes and rikshaws and bikes and cows through little villages well in excess of 70mph...

    Posted 13 years ago #

  5. crowriver
    Member

    Most terrifying experience, however, was being driven to the airport outside Varanasi at breakneck speed, dodging potholes and rikshaws and bikes and cows through little villages well in excess of 70mph...

    You don't have to travel to India to have an experience like that. Drivers behave like this in much of the Balkans, southern Italy and Poland. The idea of slowing down in villages only seems to occur when there's a visible hazard like a big tractor or something in the way. Never been to Russia yet but I imagine it's much the same. Hell the Highlands of Scotland and the Isles used to be a bit like that, maybe still are in places.

    Yet there are also cyclists in evidence in all these places. Hardy souls.
    I have cycled in Bulgaria, which was not too bad once I got used to the traffic speeds. Wearing a hi-viz tabard seemed to help: the drivers gave me plenty of room. I suspect some may have mistaken me for a traffic cop!

    Posted 13 years ago #

  6. Instography
    Member

    Sorry to get back on topic but, hang on, if the modelled increase is 25 deaths when the limit changes by 10mph and the average speed increases by 3mph as a result, and if the actual average speed on motorways is already over 70mph (which it is, although I don't have time to go and find the data now but the justification for the increase is that it's what people are routinely doing anyway and also why they won't get the savings in journey times that they claim) then the new limit would produce, err, no additional deaths because those are already in the current figures.

    They've taken the modelled effect and applied it to data that already includes that effect.

    Posted 13 years ago #

  7. chdot
    Admin

    "They've taken the modelled effect and applied it to data that already includes that effect."

    Perhaps, but surely the point is that if the limit is raised so will the actual speeds (above the legal limit) which is likely to lead to more deaths(??)

    Posted 13 years ago #

  8. Smudge
    Member

    @Instography, not a scientific basis, but my experience of recent years is that in Scotland most traffic seems to run about 65-70mph and those over it are very much in the minority (Main experience M8 and M9), however once I get a good way down the M6, and especially in the vicinity of London, the majority of private cars seem to be doing 80+, I wonder if the speeds really do vary with geography?

    If that is the case, then presumably the volume of traffic in the South would mean that the average is still over 70, so a bit of a moot point, but could lead to a variation in the effect of a higher speed limit perhaps.

    Posted 13 years ago #

  9. Wilmington's Cow
    Member

    I've noticed the same geographical split Smudge. The further south you get the more people willing to blast past there seem to be (though maybe it's the same percentage as there are also more cars in general on the roads?).

    Posted 13 years ago #

  10. Instography
    Member

    @chdot
    That's what the American says but he's talking about how drivers responded to increases from the very low Federal 55mph but it can't just be assumed that the same would happen if the limit is increased from 70mph. It might but it doesn't automatically follow that it would. At the very least, you can't headline an article based on modelled data and tenuous comparisons with another country with "80mph speed limit 'would increase deaths by 20%'" (my bold). Might or could would be more accurate.

    Can't find any country data on average speeds. On average 49% of cars exceeded 70mph in free flow conditions on motorways in 2010.

    Posted 13 years ago #

  11. Dave
    Member

    "if the modelled increase is 25 deaths when the limit changes by 10mph and the average speed increases by 3mph as a result, and if the actual average speed on motorways is already over 70mph ... the new limit would produce, err, no additional deaths because those are already in the current figures"

    Not sure I follow. At the start you point out that they modelled the increase of 25 deaths based on an increase in real average speeds of 3mph, whatever the actual real average speeds are (above or below 70mph in any given situation).

    Of course, the average speed doesn't tell us that much about what's going on, if it's just a dumb average. A lot of motorway traffic is restricted anyway (trailers and caravans, goods vehicles) and might weigh down an increase of significantly more than 3mph in those vehicles which would be able to drive at 80mph.

    It's a daft idea IMO. To exactly the wrong sort of driver it will justify going at least 10mph faster than their already ludicrous speed. As a regular motorway driver I'm quite happy with the current limit (even though I often exceed it).

    Posted 13 years ago #

  12. PS
    Member

    This is entirely non-scientific and based on a pretty small sample size, given the infrequency of my motorway driving, but I've been pleasantly surprised by the experience of sticking the car in cruise control at 68mph. Sure, there are a number of foot to the floor merchants who whizz past at 85mph+ (and these are not all exec-standard BMWs/Audis etc - just as many smaller VWs/Renaults/Peugeots, some of which don't look capable of doing more than 60...), but the majority seem to stick to the speed limit.

    Things may well be different on weekdays, but recent experince of a very busy motorway of the type you tend to get as you head south of Preston seemed to suggest that, if anything, average speeds drops as the three lanes filled up (because you can only go as fast as the car in front).

    Posted 13 years ago #

  13. Dave
    Member

    I'd really like cruise. In fact, what I'd really like is something that would limit me to an arbitrary speed as well, i.e. you drive normally, but the ECU moderates the throttle (so that in a 30 zone, you won't go over 30 even if you try to floor it).

    I've driven a car with cruise but wasn't an epic fan in town (for instance, when you'd otherwise naturally let the engine moderate your speed before a corner, it would eerily keep going!).

    Posted 13 years ago #

  14. Roibeard
    Member

    I'm a little wary of speed limiters, as they remove one of the triumvirate of collision avoidance options - brake, steer, accelerate. I suppose I've bought into the Saab/Volvo argument that power can be used to minimise exposure to risk!

    Similarly, I've only used cruise control on the open road; in town or heavy traffic, I want to be fully in control of my speed...

    I'm not one of these "better than average" drivers, so being fully engaged with the task is best!

    Robert

    Posted 13 years ago #

  15. PS
    Member

    Cruise control is solely a motorway thing for me. Certainly wouldn't want to use it on an urban road.

    Posted 13 years ago #

  16. Instography
    Member

    OK. That's two hours I'm not going to get back but at least I know how the calculation is done. When the Guardian says the Power Model uses 100 studies they're not exactly lying but it's not exactly true. The guy did look at 100 studies but mainly to dismiss them. His model of the relationship between speed and fatalities is based on one of the studies. But, OK, let's assume that it was a good study. Plugging the numbers into the formula he develops, gives an increase in fatalities of 8.5% not 20% as the Guardian reports.

    Whether the figure of 25 additional deaths is accurate, I don't know. I can't find the number of fatalities on motorways in E&W (plenty of rates). I suppose 25 as 20% of the UK fatality total seems too low. There were 45 fatalities on non-built up major roads in Scotland (that seems to be as close as you get to a motorway in SG stats) so 125 would be very low in E&W.

    So, the impact isn't already in the numbers but it's not clear what the numbers are. In Scotland it implies about 3 additional fatalities.

    Posted 13 years ago #

  17. chdot
    Admin

    "
    @jamesgleave1: Rumours going around saying #80mph plans will be dropped. Great if true, but let's hope #20mph are not dropped too. #20isplenty

    "

    Posted 13 years ago #

  18. crowriver
    Member

    New Westminster transport minister is a cyclist, so maybe the 20mph plans still have some hope left...

    Posted 13 years ago #

  19. Smudge
    Member

    @Roibeard, In some ways I agree that you can accelerate out of danger, but in my experience all normal four wheelers are so sluggish that it is not of any benefit, just manouvering at the pre-existing speed is as effective (and practically all that happens anyway). If there is time to change down and accelerate there is time to brake and/or avoid the incident.
    The only possible exemption to that in my experience is a large motorbike where the outrageous acceleration available (in any gear) makes it (accelerating at nil notice) a viable alternative.

    Our new trucks at work have, in addition to the mandatory 56mph limiter, (and "normal" cruise control) a variable "licence saver" limiter which can be set on the fly. You use controls on a column stalk to set a maximum speed (variable in 1kph/mph increments) and the truck drives normally up to the preset limit but will not drive past it.
    I was unsure of it until I drove it for half a day, every vehicle should have them! A great bit of kit, I found myself using it all the time, especially good at roadworks or in town where it's relatively easy to drift over the limit when concentrating on lots of other things.

    Posted 13 years ago #

  20. Wilmington's Cow
    Member

    I remember a Top Gear from when it was Top Gear and not Jeremy Clarkson presents Top Gear, probably early 90s, and they tested a system based on GPS. Seemed like sci-fi at the time, but the car knew what the limits of the roads were using the GPS to guage the position, and limited the top speed to the top speed of that road.

    Actually, maybe it was Channel 4's Driven...

    Anyway, the presenter thought it was impressive, but declared that it would be dangerous to be overtaking something then find you struck the limiter and were therefore in harm's way with traffic coming the other way.

    Even at the time, as a car-obsessed adolescent, I thought 'if there are cars coming the other way and the only way to overtake 'safely' is to break the speed limit then surely you shouldn't be overtaking?'

    Posted 13 years ago #

  21. Smudge
    Member

    I've wondered for some time now why this isn't an option on new cars (many with satnav fitted as standard). It should be an easy fix to get the satnav to talk to the ECU(s) and limit the vehicles max speed to the roads limits. I bet some parents would be all for the option when letting darling teenage offspring borrow their cars!

    The failed overtake/accelerate out of trouble argument will in future I suspect be viewed the same way as the "seatbelts restrict my movement so I'm more likely to crash" arguments (and similar) that I remember from my childhood...

    If the govt actually cared about road safety car speed limiters would become mandatory pretty quickly, but it seems apparent to me that most of them only care when they think there are some votes in a soundbite :-( There is no valid argument against a 70-75mph speed limiter in this country, and "smart" ones would be better.

    Posted 13 years ago #

  22. Instography
    Member

    I saw a presentation of a research project testing a similar GPS system. The limiter could be over-ridden for that overtaking reason but in normal circumstances it worked as you describe it. One of the ironic outcomes of the test was that the average speed of people with the limiters was higher than people driving unlimited cars.

    When a GPS system says 30mph it means 30mph whereas normal speedos say 30mph when the car is moving at about 27mph. Try with a TomTom.

    Posted 13 years ago #

  23. slowcoach
    Member

    There is some info on "Intelligent Speed Adaptation (ISA)" or "External Vehicle Speed Control" in evidence to the Transport Select Committee including "if all vehicles in Great Britain complied with current speed limits, there would be a 29% reduction in injury accidents and a 50% reduction in fatal crashes".

    In Scotland, in its Road Safety Framework, the government has a commitment to

    Promote the voluntary use of Intelligent Speed Adaptation ( ISA).
    Consider a pilot in Scotland to test out the effectiveness of voluntary ISA in road safety.

    Posted 13 years ago #

  24. chdot
    Admin

    "80mph limit Wales 'opt-out' call

    Wales should opt out of UK proposals to raise the motorway speed limit from 70mph to 80mph, a sustainable transport lobby says.
    "

    http://www.bbc.co.uk/news/uk-wales-south-east-wales-16636106 >

    Posted 13 years ago #

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