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General Chat Thread, Gov proposes 60mph motorway speed limit in General; One of the stated aims is to reduce pollution. Any car travelling on a road will be subject to the ...
  1. #16


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    One of the stated aims is to reduce pollution. Any car travelling on a road will be subject to the physics of drag, which increases with square of the speed (irrespective of any other factor), which means that a car travelling at 120km/h will experience 45% more drag. In modern cars that seems to translate to around 20% more fuel.

    (Also in any accident, the kinetic energy varies as the square of the speed so with that little ~20km/h you carry 45% more energy into any accident).

  2. #17

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    surely by that logic motorways need not have multiple lanes as if the first car is doing 70, then there is no congestion anywhere as everyone behind is too
    Funny you should say that. Since they have turned a single road into a dual carriageway it actually takes longer to get from one end to the other as everything backs up at the roundabouts which never happened before.

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    Quote Originally Posted by localzuk View Post
    Or, you know, they're doing it for the reason they say - to reduce pollution. Reducing speed by 10km/h would reduce emissions by up to 12-18% according to an EU study a while back (if people follow the speed limit!).
    How inflated are the manufacturers output figures? How well are the cars maintained? How old are the cars? What percentage are petrol to diesel?

    Not picking at your response, just at the very nature of the argument. Banning cars/lorries over 10 years old may go down like a house on fire but would significantly cut pollution and probably reduce the accident rate.

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    Quote Originally Posted by pcstru View Post
    One of the stated aims is to reduce pollution.
    This is the sole reason why they're proposing a speed limit cut - to comply with whatever eco- is making the running this week.
    Last edited by elsiegee40; 7th January 2014 at 08:29 AM. Reason: Language

  5. 2 Thanks to Flatpackhamster:

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    @Flatpackhamster : IMO potty mouth comments are probably best kept to more suitable forums. However strong your views, the language in here should be kept ... 'professional'.

  7. #21

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    Quote Originally Posted by Dopefish View Post
    surely by that logic motorways need not have multiple lanes as if the first car is doing 70, then there is no congestion anywhere as everyone behind is too
    Not the same situation. If people are travelling at 56, 58 and 60 in three lanes, the capacity of the road is basically full. It won't make any difference to the other drivers behind - they can't legally go any faster. Simply increasing to 70 doesn't make much difference to the road either as you'll then just have a heavy trucks at 50, other trucks at 56 and cars at 65 in the outer lane... Makes no real difference to anyone.

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    GREED's Avatar
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    Cane someone point me in the direction of evidence to show this will cut pollution? Keeping in mind engines will be running for longer as it takes longer to get there. And if so, why not 50.. or 40... or better yet don't drive at all?

    Funny how these things emerge just after rail fairs have increased...

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    Quote Originally Posted by localzuk View Post
    Not the same situation. If people are travelling at 56, 58 and 60 in three lanes, the capacity of the road is basically full. It won't make any difference to the other drivers behind - they can't legally go any faster. Simply increasing to 70 doesn't make much difference to the road either as you'll then just have a heavy trucks at 50, other trucks at 56 and cars at 65 in the outer lane... Makes no real difference to anyone.
    May I suggest you try doing a 20 mile stretch in the outside lane at 65 and not be shunted off the road by a collection of Audi's, BMWs and Mercs. Not saying anything about the legality of driving over 70 on the motorway, but I have never EVER seen anybody doing 65 in the outside lane, or 70 for that matter.

    Reducing the speed limit to 60 will mean the outside lane still has people doing 80, the inside lane still has trucks/caravans doing about 50 and the middle lane still has everyone else doing a varying speed between the two. In the same way that raising the speed limit would still have trucks/caravans doing about 50, the outside lane would get bumped up to about 85/90 and the middle lane would still have people driving a varying speed between the two.

    As an example, last week driving back down the M1, the matrix board said to slow to 50 as there were pedestrians in the road. I can guarantee you I was the only person doing 50 between that speed restriction.

  11. #25

    localzuk's Avatar
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    Quote Originally Posted by Dopefish View Post
    May I suggest you try doing a 20 mile stretch in the outside lane at 65 and not be shunted off the road by a collection of Audi's, BMWs and Mercs. Not saying anything about the legality of driving over 70 on the motorway, but I have never EVER seen anybody doing 65 in the outside lane, or 70 for that matter.
    You cannot use people who break laws as a reason to change the laws! Otherwise, what's the point of a law? Just because people drive badly, and use the lanes incorrectly doesn't mean the law should be changed to allow it. It means the police need to crack down and prosecute those muppets.

    Reducing the speed limit to 60 will mean the outside lane still has people doing 80, the inside lane still has trucks/caravans doing about 50 and the middle lane still has everyone else doing a varying speed between the two. In the same way that raising the speed limit would still have trucks/caravans doing about 50, the outside lane would get bumped up to about 85/90 and the middle lane would still have people driving a varying speed between the two.

    As an example, last week driving back down the M1, the matrix board said to slow to 50 as there were pedestrians in the road. I can guarantee you I was the only person doing 50 between that speed restriction.
    And the police should have been out in force to deal with those who were speeding.

  12. #26

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    However, shifting from ARTEMIS 130 to the more ‘realistic’ ARTEMIS 120 cycle produces a much smaller reduction of 2–3 %. This is mostly caused by the fact that when a car travels at a lower average speed, the wind resistance decreases and therefore the car requires less energy.
    So, realistically you're looking at 2-3%.
    Pinch of salt - So, once again the older, less efficient, higher drag coefficient cars are what brings the numbers up.

    A 2004 530d emits 208 g/km CO2
    A 2014 530d emits 145 g/km CO2

  13. #27

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    CO2 isn't the main pollution being targeted I think. They're more focussed on particulates and NO2, as these are damaging to local health.

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    Quote Originally Posted by CHR1S View Post
    How inflated are the manufacturers output figures? How well are the cars maintained? How old are the cars? What percentage are petrol to diesel?

    Not picking at your response, just at the very nature of the argument. Banning cars/lorries over 10 years old may go down like a house on fire but would significantly cut pollution and probably reduce the accident rate.
    Its not necessarily the cars that cause the problem, its the way people drive. Not accelerating harshly and reading the road as to not use the breaks where possible saves an enormous amount of energy / fuel / pollution. One of the main problems is drivers not keeping a good distance whilst on a motorway; I know it is impossible to do. As soon as you open a 2 second gap there will be someone else jumping into it. Although better that most countries; our collective driving standards leave much to be desired.

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    Joys I look forward to it, I stopped using the M62 and between J32-35 started going that way because it was quicker due to the managed motorway bits. Rest of it I use when going down south, maybe time to start using the A1.

  16. #30

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    Quote Originally Posted by unixman_again View Post
    I wish that I could reach 60mph on the M6 around Birmingham...
    If you use the M6 Toll you can reach that and more on top of it £5.50 well spent every time I go back to the north and back to London

    As for managed motorways they do seem to work in my use of the M6, 1 and 25 all of which have them on in sections it makes a difference you do keep moving rather than stopping, however the number of people that don't understand that the 50 in a round circle AKA the managed lower speedlimit (or other number) is the new limit not 70 and then proceed to pip horns etc when people are doing it is worrying.
    Last edited by john; 6th January 2014 at 04:56 PM.

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