roadcraft site

Come on John. Saying that people taught more than 20 years ago have no
concept of spacing is like saying that you've learnt nothing since you left
school. I got my licence 45 years ago and reaction and stopping distance was
something that was stressed in the handbook. The last, and only, time I
rear-ended someone was in similar conditions to Bill's in 1982.

Theo

 

On 19/02/2008 8:48 AM, John Dwyer wrote:

I have to disagree here (at least from my own perspective). I have been
riding for 35 years and have never read-ended anyone (although I have
been read-ended a number of times - once deliberately).

There is not necessarily a correlation between length of time since
learning and lack of knowledge of distances. Au contraire, I would
suggest that more experienced riders (I can't say the same for cagers)
have a better idea of "what's a safe distance" than a newer rider with
perhaps a little too much testosterone. What we (all) need to do is to
adopt defensive riding and the associated survival skills as a way of life.

N/

 

In aus.motorcycles on Tue, 19 Feb 2008 08:48:21 +1100

Funny how "20 years ago" is code for "a very long time" isn't it.

I got my car licence in 1980. THere was a flourishing driving school
industry even in backwards Perth. I failed the first driving test, my
instructor said it was fairly common to do so and he wasn't the kind
to lie to make someone feel better.

The problem isn't that people aren't taught things, or even that they
don't get tested.

The problem is that crashes are rare.

So that most people learn by experience that they don't need to keep
big buffer zones, especially as if they do they are disadvantaged.

Percentages hide so much. How many of these rear enders are at slow
speed? How many are injury crashes? What was the actual cause, what
made the rear-ender happen?

Zebee

 

Zebee and others,

I draw my conclusions from my observations of gaps between vehicles on the
road, and from calculations on reaction times and required braking
distances. Most of the time you will not experience problems with smaller
buffer zones as the vehicle ahead of you will take some distance to stop.
But if it does not, you will become part of whatever has happened ahead of
you. The site http://www.datacraftsystems.co.uk/techniques/index.html
refers to a two second gap, which could result in a crash at as low as 30
km/h. Even low speed, non injury crashes can involve time and money in
having repairs done, preparing report for the police, and so on.

Like many things, buffer spaces are the responsibility of the driver or
rider. New riders need information that is soundly based.

John Dwyer

 

Absolutely agree with your last point. But what has this got to do with
your quote of:

Or am I just entering senility and missing the point? Or do you work for
a branch of government?

N/

 

LOL. Normally we leave the outrageous generalisations and gross
misrepresentations of the truth here to Atec and Biggus but welcome
aboard anyway.

Nev..
'07 XB12X

 

By definition the only component of "space" is exactly that - space.
Generally it's only referred to as such when empty.

So if you want to get pedantic on our asses, start mentioning the "size"
of the space. Otherwise your average tailgating P plater can say they
leave "space" even if it is only 100cm of it.

 

On Tue, 19 Feb 2008 08:48:21 +1100, "John Dwyer"

Snip

You miss the point. You sound like some born again pratt who has had
an epiphany after having a near-miss, and now you're preaching to the
ignorant masses, and obviously we know **** all.


Bill

 

Yeebers,

The following if from one of my much earlier responses to this topic and I
hope answers your question.

I have reservations about the reference to the Two Second Rule on this site.
I completed the NSW Pre-Learner's Course some time ago. They stated that
Crash Avoidance Space consisted of Reaction Time and Braking Time. They
stated that reaction time was an average of 1.5 seconds. Leaving a two
second gap allows only a 0.5 second gap in which to give yourself the space
to stop (my interpretation). You travel at 27.8 m/s at 100 km/h. A 0.5
second gap means that you have allowed only 13.9 metres to stop at 100 km/h.
May the Force be with you.

A gap of 4 seconds at 100 km/h is more realistic in my opinion. A three
second gap means that you will have to stop from 100 km/h in 42 metres.
This is a 0.94g stop. Allow a 3 second gap if you can reliably do 0.94g
stops, otherwise allow a 4 second gap at 100 km/h.

48% of all collisions in the ACT are rear enders. What any rider does is up
to him or her.

 

I have reservations about the reference to the 1.5 second reaction time.
I reckon the average person could react to something occurring in
front of them in much, much less than 1.5 seconds. Hell, I reckon a
person doing a headcheck could react to something which occurred in
front of them, while they were facing the wrong direction in less than
1.5 seconds.
The other day on the cricket Ch9 replayed a catch in slow motion. The
ball took 0.76 seconds from the bat to Symonds hand, which he caught at
full stretch to his left with his hand merely cms above the ground. He
might look like a monkey but his arms aren't that long.

Nev..
'07 XB12X

 

In drag racing, a 0.4 second reaction time is considered perfect.

First time I took the Pig for a run a got a 0.411 reaction time. Was
pipped for the prize for the best reaction time of the meet by some
arseclown who got 0.409. Beaten by two-thousandths of a second...

 

Yeah, but that is when you are anticipating something happening. When
you aren't expecting anything, about 1.5 would be a closer bet.

 

I doubt I'd react even that fast on the Nullarbor if an emu suddenly
appeared in front of me.

Theo

 

A few days ago the owner of Balls Engineering(?) in Melb was killed
after he fell off his bike.

Its said that the fall may not have killed him, but the guy behind was
too close, had nowhere to go, and ran over his neck!

There are other things to worry about than just stopping, there is
also avoidance of obstacles. 42 metres sounds enough for me to be able
to take evasive action.

SteveB

 

Nobody expects the Spanish Inquisition!...

 

Really?

And with all that practice too....


G-S

 

Seriously though, in the cut and thrust of city traffic, with lane-splitting
etc, you might achieve a reaction time of between .5 and 1 second. After
riding for six or more hours with no traffic going your way and a vehicle
coming the other way every 20 minutes or so, your reaction time to an
unexpectant event, (emu travelling at 40+kms/h crossing the road at right
angles), is going to be slower than that.

Theo

 

That's a pretty exceptional circumstance involving something completely
unexpected and unpredictable. The original discussion was about
reaction time to something happening in front of you, which you are
generally watching, and probably concentrating on.. ii.e. following
another vehicle at a particular distance.

Nev..
'07 XB12X

 

In aus.motorcycles on Wed, 27 Feb 2008 00:33:04 +1100

It's the concentrating bit....

THe place most people tailgate is higer speed multilane roads like
freeways and motorways. Which are also the more boring roads...
People switch off more often.

On the other hand, there aren't that many crashes on them because
there are few reasons for one to occur.

Zebee

 

But people who are 'tailgating' probably ARE concentrating on what's
going on. Their reaction time will probably be optimal.

Nev..
'07 XB12X