Multi car pile up on the motorway

Jonnycoupe said:
Something tells me a car cannot stop instantly anyway, why its being supposed that the Insignia did isn't really appropriate.
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I was about to say that - a 2 second gap isnt because you can stop in 2 seconds. Unless the car in front drives into a 10 foot wide concrete wall it isnt going to stop instantly.
 
Will Gill said:
I tried to work that out earlier,

needless to say I'm crap at maths and my results look quite comical next to yours :p
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the flaw in my maths is that i cant find a stopping distance in feet from 70mph for the 330i.

Most of the car tests on autocar are of really expensive cars with great brake so used a hot hatch instead (Focus RS was first to hand)

The other flaw is that none of the above takes into account the variables - the tread of the tyre (did it have cheap tyres or did it have Contis on for example ?), the quality of the road surface, the state of the road (ie wet/ dry ?)

Theres just so many variables its untrue. And its pointless going any further with the mats, because even if he did stop, the woman behind would just have shunted him harder ...
 
MrLOL said:
the flaw in my maths is that i cant find a stopping distance in feet from 70mph for the 330i.

Most of the car tests on autocar are of really expensive cars with great brakes.
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I dont know how useful this figure is but the Autocar test of my car has it doing 60-0 in 2.9 seconds.
 
[TW]Fox;18160269 said:
I was about to say that - a 2 second gap isnt because you can stop in 2 seconds. Unless the car in front drives into a 10 foot wide concrete wall it isnt going to stop instantly.
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Presumably hitting a 30mph when you're doing 70mph is going to reduce the stopping distance.

I wonder how much by ?


[TW]Fox;18160284 said:
I dont know how useful this figure is but the Autocar test of my car has it doing 60-0 in 2.9 seconds.
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not so much, because during that 2.9 seconds its speed is constantly decreasing, so is the distance it travels per second. Difficult to work a distance out from that. Does it quote distance too ?
 
MrLOL said:
not so much, because during that 2.9 seconds its speed is constantly decreasing, so is the distance it travels per second. Difficult to work a distance out from that. Does it quote distance too ?
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Assuming linear deceleration, 60mph - 0mph would cover

1/2 (27.3ms * 2.9s) = ~40m
 
My girlfriend has a 5~10 mph crash into a wall from the ice a few weeks ago, she felt totally fine all day. The next day, she could barely walk.. Just a heads up for you Tom
 
MrLOL said:
not so much, because during that 2.9 seconds its speed is constantly decreasing, so is the distance it travels per second. Difficult to work a distance out from that. Does it quote distance too ?
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You can work it out with the info there.

distance = 0.5 (31.3 * 2.9)
distance = 45m

If that helps you there. To give you an idea 70mph = 31.3 m/s.

Edit - missed the post above, plus I did it from 70mph. :p
 
[TW]Fox;18160657 said:
What is the official stopping distance in the HC from 60mph?

edit lol it's 73 metres!
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The HC is hopelessly out of date, a modern HGV can match some of the braking distances quoted (empty, I grant you!)
 
[TW]Fox;18160657 said:
So my car stops from 60mph in 40 metres.

What is the official stopping distance in the HC from 60mph?

edit lol it's 73 metres!
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That will be without reaction time. That will be autocar driving to a specific point then hitting the brakes at that point.

Highway code say the reaction time is 18m plus 55m actual braking distance

So if your car stops in 40 metres from 60, the stopping distance i was using of 45 Metres (excluding thinking distance) for 70mph from a Focus RS sounds about right.
 
snowdog said:
People will fill that gap, motorways are extremely busy at times, people will not wait at junctions/sliproads until there is enough space, they will simply squeeze in.
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Even if someone does fill in the gap, that's not exactly the end of the world is it?

You just slow down a little so you've got a decent gap again between you and the car in front... It's not rocket surgery you know! :p
 
MrLOL said:
So if your car stops in 40 metres from 60, the stopping distance i was using of 45 Metres (excluding thinking distance) for 70mph from a Focus RS sounds about right.
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You think a Focus RS travelling 10mph faster would only take 5m more to stop despite the fact stopping distances increase significantly as speed increases?

:confused:

Edit: Just double checked the figures. 2.7 seconds 60-0 not 2.9 seconds. With the following comment:

Autocar said:
The wet weather had little effect on braking times. It's ventilated front and solid rear discs brought the 530i to a standstill from 60mph in just 2.7 seconds - one of the best times we've ever recorded on a damp track
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[TW]Fox;18161347 said:
Can somebody recalculate the braking distance based on 2.7 seconds?
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It's just 1/2 (change in speed in m/s * time) = distance covered

You're looking at the area under the line on a graph of velocity against time. Assuming constant deceleration, the line will just be a straight line and the area/shape it draws is a triangle, so you're effectively just working out the area of a triangle.
 
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