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nebbian said..

rod_bunny said..
I'll try another analogy for the "Its simple physics" team...

Would you rather be shot in the face with:
a) .44 magnum (110km)
or
b) .22lr (90kmh)

The difference in energy being transmitted to the body between the 2 is massive - but both are arguably gonna be fatal.

"But I don't want to get shot in the face" I hear you cry?

So, how about we get rid of the guns? Then we are waaaaay less likely to be shot. (ie Ensure that dickhead drivers are removed from the roads)


Do we legislate to cover the lowest denominator (eg BB guns for everyone / 50kph) OR actually deal with the real problem?

Rod_bunny, perhaps you've forgotten about stopping distance.



Dropping the speed limit by 10 km/h reduces the stopping distance by around 15 metres (on dry tarmac), which is the difference between a 50 km/h head on, and stopping before you hit the other guy. Massive difference in survivability.

A good graph you've found there Nebbian. Even if it has taken me a little while to get my head around it. You're basically saying that a 10kph difference in speed when you see a problem needing brakes will result in a 50kph difference in collision speed!

You can also use the graph for intermediate scenarios. Let's say you've hit the brakes at 100kph and collided at 50kph. You should survive, that's about the speed they do crash testing at. You used up 84 metres of your 98 metre stopping distance when you collided at 50kph. If you had been doing 110, at the 84 metre mark you still need a further 29 metres for a full stop. Looking at the graph again 29 metres is about 72 kph. You won't walk away from a 72kph head on. In this instance a 10 kph difference in cruise speed has resulted in a 22 kph difference in collision speed.

Remember this when you see something up ahead requiring you to hit the skids. At that instant, if you've understood this graph, you'll be very much wishing you did not have an extra 10kph on board.

^^^^ The problem with that is it fails to take into account the increase in reaction time due to
hangover
bogan
don't care
asian tourist looking at flowers
euro in wicked camper singing and chatting
oldies in a daze
..... and that seems to be half the traffic on this particular road. I'd prefer switched on, fully rested, sane people in modern cars doing 120kph any day.

The physics is complex but I vaguely recall the inverse square rule applies. The difference in energy from a 30 km crash verses a 90km crash isn't a factor of three, its actually nine times. So dropping 10km down from 110 has a far greater effect than dropping it from 60 down to 50.

Rod - a head on crash at 110km/hr isn't an immediate death sentence, not by a long shot, but fark me, give me the choice between a head on at 110 or 100, I'll take the lower speed. I might just survive it, I'll take the might even it it only increases my chance of survivability by 5%.

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Mark _australia said..
^^^^ The problem with that is it fails to take into account the increase in reaction time due to
hangover
bogan
don't care
asian tourist looking at flowers
euro in wicked camper singing and chatting
oldies in a daze
..... and that seems to be half the traffic on this particular road. I'd prefer switched on, fully rested, sane people in modern cars doing 120kph any day.

Well you hold the other variables constant when looking at the sensitivity to the variable of interest. It doesn't invalidate your conclusions concerning that variable. Yes fully rested and switched on people will pass by without incident at 120kph. But when that fully rested person doing 120kph strikes a problem with one of the others you mention, they're going to wish they were doing 100kph.

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Chris6791 said..
The physics is complex but I vaguely recall the inverse square rule applies. The difference in energy from a 30 km crash verses a 90km crash isn't a factor of three, its actually nine times. So dropping 10km down from 110 has a far greater effect than dropping it from 60 down to 50.

Rod - a head on crash at 110km/hr isn't an immediate death sentence, not by a long shot, but fark me, give me the choice between a head on at 110 or 100, I'll take the lower speed. I might just survive it, I'll take the might even it it only increases my chance of survivability by 5%.

Yep... just like the wind. (See, it is a windsport thing )


No... getting hit at 110 maybe isn't a death sentence. You might live. (People have lived from crashes faaar in excess of 110 - Richard Hammond at 460 odd? )
Its still a might & a maybe... taking chances with the end result of something that was avoidable.

If you'd rather have the head on at a lower speed... why not 80? or 60?


I get the physics. But I purposefully left out all the variables like braking distance, reaction time (bogans, drunks, wobblies, vehicle age, ABS, Asians, Oldies, fatigued etc) to concentrate on speed (because that is the ONLY thing the Govt is really doing) relative to the outcome of the crash.

Lewis Hamilton in his brand new AMG doing 100 (who with his amazing mad skills brings his car to a stop) is still going to be just as dead when the hungover bogan in his ****box 4" lifted patrol with paddle tyres for Lano has a micro sleep and drifts onto the wrong side of the road.

Honestly you could leave speed as fixed and play with the rest of the variables to conjure up any scenario you liked. Your survivability could be down to any other number of other variables (Car age, roadworthiness, where the car was hit, where you sat, Takata airbag, just plain old bad luck, etc etc etc).

All the other factors, are more important because they increase the potential of the crash.

Anyone who has had any exposure to heath and safety knows that the crash is the LAST thing - everything else is a leading indicator. Given that everyone on here has an anecdote or 3, observing the behaviours that lead up to a crash on just that road alone. The commonality of the observed behaviour would suggest that speed, is not the main factor.


Personally I would rather have a 98% chance of never having an accident, rather than debating the >5% chance I might live, because on that road, we know its going to happen.


If the govt was serious, I mean actually really serious, about reducing the death toll they wouldn't mess around with just dropping 10.
But its the only factor that they can control by putting a cash collector on the side of the road.

I've done the OSH thing too, improving the road will engineer out some of the idiot decisions made on the road up there but that isn't going to happen anytime soon. It'll cost too much money, probably need many more deaths before the political and public will is there to spend $100 million or more. We''l probably get the new road when they forward budget for the desal plant I think will go in south of Ledge Point at Breton Bay - the'll need a wider road to get the oversize loads in; so you'll get the road you want, with the trucks you don't.

Coincidentally, crashes on the Forrest Highway were unexpectantly high when they opened up that beautiful, straight dual carriage way. People got so fkn bored with such a straight, monotonous road they simply fell off it (it's still happening). At least a rollover is a better option than a head on I guess...

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Chris6791 said..
I've done the OSH thing too, improving the road will engineer out some of the idiot decisions made on the road up there but that isn't going to happen anytime soon. It'll cost too much money, probably need many more deaths before the political and public will is there to spend $100 million or more. We''l probably get the new road when they forward budget for the desal plant I think will go in south of Ledge Point at Breton Bay - the'll need a wider road to get the oversize loads in; so you'll get the road you want, with the trucks you don't.

Coincidentally, crashes on the Forrest Highway were unexpectantly high when they opened up that beautiful, straight dual carriage way. People got so fkn bored with such a straight, monotonous road they simply fell off it (it's still happening). At least a rollover is a better option than a head on I guess...

^This is what I'm talking about.

Although I would rather they "engineered" the clowns off the road



Just for ****s and giggles I've been reading up on crash metrics.
50g seems to be a fatal "dose" of what the body can handle within itself within the time of a crash pulse (ie not taking into account secondary impacts etc.)

My long winded point being...
Yes; the slower you go, the lower the forces, BUT over a certain speed (that is still a long way below 100) it becomes largely irrelevant. You don't get any less dead from reducing 120g to 50g.

I think this has been plotted the wrong way round but you get the idea...

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rod_bunny said..

Chris6791 said..
I've done the OSH thing too, improving the road will engineer out some of the idiot decisions made on the road up there but that isn't going to happen anytime soon. It'll cost too much money, probably need many more deaths before the political and public will is there to spend $100 million or more. We''l probably get the new road when they forward budget for the desal plant I think will go in south of Ledge Point at Breton Bay - the'll need a wider road to get the oversize loads in; so you'll get the road you want, with the trucks you don't.

Coincidentally, crashes on the Forrest Highway were unexpectantly high when they opened up that beautiful, straight dual carriage way. People got so fkn bored with such a straight, monotonous road they simply fell off it (it's still happening). At least a rollover is a better option than a head on I guess...

^This is what I'm talking about.

Although I would rather they "engineered" the clowns off the road



Just for ****s and giggles I've been reading up on crash metrics.
50g seems to be a fatal "dose" of what the body can handle within itself within the time of a crash pulse (ie not taking into account secondary impacts etc.)

My long winded point being...
Yes; the slower you go, the lower the forces, BUT over a certain speed (that is still a long way below 100) it becomes largely irrelevant. You don't get any less dead from reducing 120g to 50g.

I think this has been plotted the wrong way round but you get the idea...

Fair enough, but one of the variables that you've kept constant is that the brakes are never applied. Although that's often true apparently, maybe even for both vehicles? It's when you allow for some braking that the differences are huge. No one was hurt in this video, the truckie is thankful he didn't have an extra 5 kph of speed.

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Ian K said..
Fair enough, but one of the variables that you've kept constant is that the brakes are never applied. Although that's often true apparently, maybe even for both vehicles? It's when you allow for some braking that the differences are huge. No one was hurt in this video, the truckie is thankful he didn't have an extra 5 kph of speed.

Because in some cases they aren't. Asleep, distracted, a bunch more other variables pre crash.
Plus when the brakes were applied but:
worn tyres
worn road surface (There is a roughness standard)
wet, gravel,
overloaded.
only one person brakes.

In the vid.. a near miss. Who knows what speed the truck was doing. The limit? 10 under/over?
What if:
The kid, ran out 0.5 sec later, or zigged instead of zagged.
The truck driver was checking his GPS.
The camera op didn't honk his horn.



PSAs like this^ are contrived. They show the end result based around a backward calculation to show the crash.
"2 identical cars, one going faster, but he sees the truck first and stops. The one going slower was checking his phone and doesn't"





Thankfully PSAs are starting to focus on all the other issues.

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rod_bunny said..

Because in some cases they aren't. Asleep, distracted, a bunch more other variables pre crash.
Plus when the brakes were applied but:
worn tyres
worn road surface (There is a roughness standard)
wet, gravel,
overloaded.
only one person brakes.

In the vid.. a near miss. Who knows what speed the truck was doing. The limit? 10 under/over?
What if:
The kid, ran out 0.5 sec later, or zigged instead of zagged.
The truck driver was checking his GPS.
The camera op didn't honk his horn.

But once again! All those other variables you list don't invalidate the sensitivity of a crash situation to speed. Separating variables is one of the basis of modern calculus. It works! It's completely valid to do so!
Isaac Newton 1687. en.wikipedia.org/wiki/Calculus
https://en.wikipedia.org/wiki/Partial_derivative.

You could do a sensitivity test to tyre tread depth while holding speed constant if you like. Crash results might be almost as sensitive this as speed. Who knows? But bald tyres are already illegal

We had a truck vs. house battle today for a change

www.watoday.com.au/national/western-australia/careless-driving-truck-crashes-into-wanneroo-home-20171114-gzkyna.html

Truck won from the looks of it.

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Ian K said..

rod_bunny said..

Because in some cases they aren't. Asleep, distracted, a bunch more other variables pre crash.
Plus when the brakes were applied but:
worn tyres
worn road surface (There is a roughness standard)
wet, gravel,
overloaded.
only one person brakes.

In the vid.. a near miss. Who knows what speed the truck was doing. The limit? 10 under/over?
What if:
The kid, ran out 0.5 sec later, or zigged instead of zagged.
The truck driver was checking his GPS.
The camera op didn't honk his horn.

But once again! All those other variables you list don't invalidate the sensitivity of a crash situation to speed. Separating variables is one of the basis of modern calculus. It works! It's completely valid to do so!
Isaac Newton 1687. en.wikipedia.org/wiki/Calculus
https://en.wikipedia.org/wiki/Partial_derivative.

You could do a sensitivity test to tyre tread depth while holding speed constant if you like. Crash results might be almost as sensitive this as speed. Who knows? But bald tyres are already illegal

Exactly right, It doesn't invalidate Speed any more than it invalidates any other variable - so why concentrate on just speed esp at the exclusion of all other variables?

The mantra of "Speed Kills" "Drop 5" at the exclusion of everything else is disingenuous at best and fatal at worst.



"Separating variables is one of the basis of modern calculus. It works! It's completely valid to do so! "

Which is why I removed them. To show that above a certain speed*, it becomes irrelevant what the speed is.
*"which is way below the now "safer" speed of 100"

ie All things being equal, changing the speed from 110 to 100 doesn't make it safer by an amount that will make a dramatic difference, esp on that road and esp given its unique issues.


"You could do a sensitivity test to tyre tread depth while holding speed constant if you like. Crash results might be almost as sensitive this as speed. Who knows? But bald tyres are already illegal"

Yes... it is, but tyres cant be checked by a camera as you drive passed.



Almost every trip I make back from up north, I and everyone else get pulled over just south of The Overlander, by Fisheries, to check for me having more fish than allowed.
Can someone explain why Fisheries can get their **** together enough to pull everyone over to check for something, that is not going to kill anyone... but the Police or DoT cant manage to do it for defective vehicles, drunk/drugged, overloaded?

Don't wanna get held up by DoT for an inspection? Leave Earlier.

PS WA doesn't have an annual vehicle roadworthy check. Why?




As Cisco stated earlier, I would rather have a sober, attentive, competent, driver doing 110 than "choose any other variable" doing 100.

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novetti said..
We had a truck vs. house battle today for a change

www.watoday.com.au/national/western-australia/careless-driving-truck-crashes-into-wanneroo-home-20171114-gzkyna.html

Truck won from the looks of it.

How fast was the house going?

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rod_bunny said..

novetti said..
We had a truck vs. house battle today for a change

www.watoday.com.au/national/western-australia/careless-driving-truck-crashes-into-wanneroo-home-20171114-gzkyna.html

Truck won from the looks of it.

How fast was the house going?

According to some it will be the house's fault...not giving way to a faster vehicle...