Does speed kill?

Dont forget that Joe Bloggs buying budget ling longs for his 5 star NCAP rated car to save a few pounds might struggle to slow down as fast at 40mph in the wet compared to someone going 50mph but with premium UHP tyres on their wheels....

So many factors will decide on whether a motor accident is fatal or not, the speed is just one of those many factors.
 
Speed doesn't. It's the deceleration that kills.

"guns don't kill people, rappers do" - had me stitches there :)
 
Energize said:
I just showed you using one of the oldest equations in the book, (F=ma) that is incorrect.
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no you didn't air resistance is a negligible increase especially in the sub 20 region.

momentum is the thing your forgetting.
 
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there you go energize


50% off speed in the last 5m. if those last 5m happen to be inside the thing you're going to hit then you're hitting a lot lot faster.
 
What you said and what the video implies are two different things.

The video takes into account reaction time and refers to a relative change in velocity not absolute.

So yes absolutely going a few mph faster has a big impact on impact velocity in a real crash scenario, because of higher inital velocity combined with the reduced braking time.

However at the same time, newtons laws of motion irrefutably demonstrate that when a vehicle brakes it loses the most speed in the first few metres and the least in the last few metres of braking.
 
Energize said:
However at the same time, newtons laws of motion irrefutably demonstrate that when a vehicle brakes it loses the most speed in the first few metres and the least in the last few metres of braking.
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that assumes that your brakes work just as effectively at high speeds as low and your tyres grip just the same and that you can apply the same breaking force at the higher speeds without skidding or locking up or losing control.


i'm going to guess you don't drive or ride anything with an engine?
 
Energize said:
Loss of velocity is more rapid at higher speeds due to the disproportionately higher energy losses to due air resistance etc, so an extra 5mph at the point of braking would actually equate to less than 5mph extra at the point of impact. F = ma, so a = F/m, m is constant, but F increases as speed increases therefore de-acceleration is greater.
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I have to agree with tefal on this one.

There have been tests done, testing speed at different points of an emergency stop - using the same car, same road conditions, same bit of road etc to rule out as many other factors as possible to show how speed affects your stopping.

The car drove along at 70mph and performed an emergency stop starting at a point signalled by cones, so this is not testing reaction times. The car was then driven along at 100mph and performed the same emergency stop. This is an increase of 30mph.

At the point the first car stopped, the second car was still travelling 72mph.

An increase in speed of 30mph has changed the outcome from no collision to a collision of 72mph, if the obstacle/car/whatever was at a point where you could just stop in time from 70mph.

edit: just had a thought about this. You may be right in that if you were to plot the speed of a vehicle against time, you would see a larger deceleration to start with and less deceleration towards the end. However you are not taking into account the distance travelled. At a high speed you may reduce your speed quicker, but you travel a much further distance in the time it takes to reduce your speed.
 
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Phantom Shadow said:
edit: just had a thought about this. You may be right in that if you were to plot the speed of a vehicle against time, you would see a larger deceleration to start with and less deceleration towards the end. However you are not taking into account the distance travelled. At a high speed you may reduce your speed quicker, but you travel a much further distance in the time it takes to reduce your speed.
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Of course braking distance is increased that is not in dispute, I am simply stating newtons laws of motion which show that Δa is greatest at higher velocities.
 
Yes but what I was getting at with that was that at the start of the stopping distance you travel disproportionately further even though you have a drop in speed - meaning that at a set distance if you are going 1mph faster to start with you pass that point going >1mph faster.
 
Energize said:
Of course braking distance is increased that is not in dispute, I am simply stating newtons laws of motion which show that Δa is greatest at higher velocities.
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and you cover more ground. think about it smaller loss of acceleration but your moving less distance = more speed lost per m (remember we're not talking time but distance)

than bigger deceleration but spread out over a longer distance.
 
they need to remove comfort from cars. keep people on their toes, looking at the road. also do not grant licences to dangerous people and tests every 10years.

also, scrap all the awful cars on the road. i mean, i talk to some people that have NEVER had the oil changed in their car even after 10 years... brake pads?!? what are they? bald tyres?

up the limit, reduce numbers or people who take driving for granted.
 
stuman said:
they need to remove comfort from cars. keep people on their toes, looking at the road.

also, scrap all the awful cars on the road. i mean, i talk to some people that have NEVER had the oil changed in their car even after 10 years... brake pads?!? what are they? bald tyres?

up the limit, reduce numbers or people who take driving for granted.
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Okay let's see...

1: Removing comfort from a car makes it awful so you want to actually scrap the very cars you want to see on the roads?

2: How do you discern who is a dangerous person? I have no criminal or bad driving record but I'll pull out a Mac10 in under 3 minutes I'll have you know?

3: If people have not had their brakes or tyres changed for so long that they're virtually an unknown thing then how are they using those cars on the roads given that an MOT will flag and fail those cars? Does that mean you're admitting to knowing people who drive cars unfit for the road (read: the very cars you want to see and at the same time scrap!) illegally?!

4: And to end it all off you want to up the speed limit so people with uncomfortable scrap worthy cars with no brakes or tyres can cruise along being a danger to the rest of us?

Tsk tsk.
 
MagicBoy said:
Speed doesn't kill. Bad driving does, of which speed may be a factor.
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Yup. it's very subjective, but some drivers are utterly oblivious to their surroundings, no concept of speed or spatial awareness, so a line has to be drawn at some point.

Where that line is drawn, well that's contentious lol.
 
Nitefly said:
Speed doesn't kill, but driving too fast does.
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Over-simplifications and cliches, this thread has them in spades.

People drive fast and don't kill anyone on a daily basis.

Other people get knocked down at killed at 20 MPH.

Sometimes you just get unlucky.
 
I'd say for example, that taking all factors into account, it may well be safer to drive 80 in a 40 at 3AM than to drive 50 in a 40 in the middle of the day.

But does that mean it is 'worse' to drive 50 in a 40 in the middle of the day?
 
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