Thread: Irate police hunt 'missile moron' motorbike rider

Originally Posted by Dougal

Friction coefficient of ~0.8 (standard road tyres), 60km/h (16.66m/s) to zero.
Works out to 17m to stop from 60 to 0. Plus reaction time.
Works out to 31m to stop from 80 to 0. Plus reaction time.

Now these figures are highly conservative. The best cars are stopping from 100-0 in about 30m. That gives them a grip on the road of ~1.28.

Which is a 80-0 distance of 19.2m
Which is a 60-0 distance of 10.8m

Every "safety" related video or presentation I have seen on speed has been complete and utter bull**** from a physics perspective.
However, if you go to a racing driver training type presentation, they have it right.

Dougal.

I am sure your friction coefficient numbers are right. But I think the distance expands somewhat when you add in drivers reaction times, plus in most real world scenarios we are not all blessed with cat like reflexes or perfectly prepared cars with excellent tyres and brakes on great surfaces!!

Plus we are in Oz not Kiwiland, noting you appear to reside in the land of the long white cloud so that has to be factored in, -ve or +ve I will let you decide.

Regardless, my point was that there is always someone who thinks they can do it better/fast etc. than they actually can and when that someone is a repeat driving offender arguing about speeding and stopping distances it is a little disconcerting!

Regards,

George

Originally Posted by vnx205

There is at least one important difference.

Drivers on the autobahn are expecting to encounter other vehicles doing 255km/h. Drivers on the Hume Highway, quite reasonably, don't expect that.

No, they don't....but buses here don't do 80, they go 100kph, so do trucks, and with 600hp+, they go up hills that fast too.
The Hume is easily capable of 130KPH limit...trucks (100k limit)& slower vehicles in the left hand lane....overtaking or quicker vehicle in the right hand lane.....would make for better more sensible driving, and would avoid the "follow me" situation where you could have any number of cars following a truck at around 98/102kph.....I've been in that situation many times, & I've had to exceed the speed limit to rid myself of it....absolutely ridiculous.
Do I think things will ever change?....NO.
Cheers, Pickles.

Originally Posted by vnx205

There is at least one important difference.

Drivers on the autobahn are expecting to encounter other vehicles doing 255km/h. Drivers on the Hume Highway, quite reasonably, don't expect that.

Having lived in Germany a few times, I've been on German Autobahns more times than I care to remember. The other point to remember on top of VNX205's point above, is that is you exceed the recommended speed limit of 130km/h then you are automatically deemed at least partially liable in the case of an incident.

And in Germany, people understand the phrase "lane discipline".

Originally Posted by Pickles2

.... .... ...
The Hume is easily capable of 130KPH limit.
... .....

That may be so, but that wasn't the point of my post.

If the speed limit on the Hume was 130 km/h, most other drivers would expect that some of the other vehicles around them might be doing 130 or 140. At the moment they have very little reason to expect to find other vehicles doing much more than 110. If they were doing 110, they normally wouldn't allow for the possibility that something might approach from behind at a closing speed of 163 km/h.

Originally Posted by vnx205

That may be so, but that wasn't the point of my post.

If the speed limit on the Hume was 130 km/h, most other drivers would expect that some of the other vehicles around them might be doing 130 or 140. At the moment they have very little reason to expect to find other vehicles doing much more than 110. If they were doing 110, they normally wouldn't allow for the possibility that something might approach from behind at a closing speed of 163 km/h.

"closing speed of 163KPH"?...Well, I wouldn't expect, or want to expect, that either!!
I don't know whether we're at cross purposes here mate?, but I certainly don't support 273ks....but I do support a Hume limit of 130Ks.
Cheers, Pickles.

Originally Posted by Pickles2

"closing speed of 163KPH"?...Well, I wouldn't expect, or want to expect, that either!!
I don't know whether we're at cross purposes here mate?, but I certainly don't support 273ks....but I do support a Hume limit of 130Ks.
Cheers, Pickles.

It seems we are. Sorry about the confusion.

Originally Posted by DiscoWeb

Dougal.

I am sure your friction coefficient numbers are right. But I think the distance expands somewhat when you add in drivers reaction times, plus in most real world scenarios we are not all blessed with cat like reflexes or perfectly prepared cars with excellent tyres and brakes on great surfaces!!

Plus we are in Oz not Kiwiland, noting you appear to reside in the land of the long white cloud so that has to be factored in, -ve or +ve I will let you decide.

Regardless, my point was that there is always someone who thinks they can do it better/fast etc. than they actually can and when that someone is a repeat driving offender arguing about speeding and stopping distances it is a little disconcerting!

Regards,

George

Reaction times certainly. I think if you can't react within a second then you shouldn't be on the road.
1 second at 100km/h is a hair less than 28 metres.
If you are following a car 2 seconds behind at 100km/h then you are about 55m behind them. Personally I find 2 seconds to be just uncomfortably close, but even then the car in front would have to stop dead to be unavoidable.

The 0.8 figures represent below average tyres on below average roads. The 1.28 figures represent hot sticky tyres on dry clean tracks.
Most vehicles will be between the two unless conditions are particularly awful (snow forecast here).

What is really interesting, get these clowns to draw a picture of a car cornering and which direction they think it will go if it loses traction.

Originally Posted by DiscoWeb

The attitude of some of the young men and women scared me more than the data and information presented.

One wanted to argue with a presenter about the accuracy of data on stopping distances, suggesting his "Fully sick" Nissan/Subaru/Commodore V8 would easily stop in less than 10m from 60 or 80kph despite the scientific evidence saying it took say 60m. No amount of discussion would convince him that he was wrong, Unbelievable !!



George

Originally Posted by Dougal

Friction coefficient of ~0.8 (standard road tyres), 60km/h (16.66m/s) to zero.
Works out to 17m to stop from 60 to 0. Plus reaction time.
Works out to 31m to stop from 80 to 0. Plus reaction time.

Now these figures are highly conservative. The best cars are stopping from 100-0 in about 30m. That gives them a grip on the road of ~1.28.

Which is a 80-0 distance of 19.2m
Which is a 60-0 distance of 10.8m

Every "safety" related video or presentation I have seen on speed has been complete and utter bull**** from a physics perspective.
However, if you go to a racing driver training type presentation, they have it right.

I have actually seen a stop on a wet track (it was the old Amaroo) from 60 (or was it 50?) km/h in two and a bit car lengths from a designated line. (Nissan Bluebird, road radials, high tyre pressures)

I could do it in less than three lengths consistently, including changing lanes. (it was a lane change/stop exercise, and no bloody ABS/stability control either) I did have windscreen wipers, indicators and God only knows what going from some fancy wheel spinning
Mark Skaife kept cleaning up witches hats

Alan Grice was the smart arse that did it in two, but he'd practiced that particular stop a lot. (yes, it was a very long time ago )