" ---- always to drive and think of speed in feet per second instead of in miles per hour, and you will at once become a hundred per cent better and safer driver. All you have to do is to add one half to the figure of your speed in m.p.h. and you will get your speed in feet per second. Any child can do that.
The other aspect of road safety touches what is called kinetic energy, which means the moving force possessed by a vehicle in motion. I can't give you a more detailed explanation, but another way to put it is to refer to kinetic energy as the kick possessed by a moving vehicle. A small motor oar weighing about a ton and moving at a speed of 40 miles per hour strikes the same blow as eighteen ten-ton steam rollers travelling at their highest speed, which is 3 miles per hour.---- "
from The Listener October 1937, p. 892. (yes 19thirty7) See
www.cut-the-knot.org/arithmetic/rapid/safety.shtml
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They sound good tips to me, and well worth bearing in mind.
Another one is to think of the 2-second safety zone as the same in yards (metres) as your speed in mph. (eg 60mph = 88 feet per second; 2 seconds = 176 feet = approx 60 yds)
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They sound good tips to me, and well worth bearing in mind. Another one is to think of the 2-second safety zone as the same in yards (metres) as your speed in mph. (eg 60mph = 88 feet per second; 2 seconds = 176 feet = approx 60 yds)
Can't fault the arithmetic Cliff (which is more than I can say about the original article referenced) but, whereas I can count 2 seconds quite easily, I couldn't tell you whether I was 50 or 70 yards behind the car in front.
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Can't fault the arithmetic Cliff (which is more than I can say about the original article referenced) but, whereas I can count 2 seconds quite easily, I couldn't tell you whether I was 50 or 70 yards behind the car in front.
That's true, but either way it is an awful lot further than most people think, and a lot bigger gap than most people keep.
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This usefully illustrates the fact that the kinetic energy of a moving object varies with the square of the speed. So, a doubling of speed increases the kinetic energy of the vehicle by a factor of four.
Not only does this make any impact much more serious, but shows how much energy brakes have to absorb as the speed increases. It also shows why it's difficult to get impact absorbing bumpers to resist damage at much more than a few miles an hour.
Regards
John S
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'Only a fool breaks the two second rule.' Remember that? Who says that public information films don't work?
Richard Hall
bangernomics.tripod.com
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Tailgateing car drivers should be given a 1970's jap bike to ride on for the winter. Theres nothing like trying to do an emergency brake in the wet!!!
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I always found the chevrons on the M1 southbound between Watford Gap and Northampton a good guide. Always keep at least two chevrons behind the vehicle in front. Haven't beenup there for a few years so don't know if they're still there.
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'Only a fool breaks the two second rule.' Remember that? Who says that public information films don't work?
Except my first driving instructor used to say it so slowly that it took four seconds. Leaving me to conclude "you obviously don't trust one of either a) the rule or b) my ability/intention to apply it, so why bring it up". Being given a rule but not knowing how to apply it was worse than having no rule at all.
Above 38 and a bit mph, two second separation is less than the highway code stopping distance. At 70mph it's only two thirds of the stopping distance.
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"At 70mph it's only two thirds of the stopping distance."
It (2 seconds) is still a much bigger gap than most people leave on the motorway, hence the pile-ups in fog. Mind you, there's probably too much traffic on some motorways for everyone to leave that big a gap - whenever I do, someone plugs it!
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"the same blow as eighteen ten-ton steam rollers"
Or a 4lb shell travelling at 1000mph...
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