The Best Advert for ABS

cachaciero · Post by **cachaciero** » 20 Dec 2009, 16:50

DickieG wrote:The correct reason behind and ABS equipped vehicle taking longer to stop on snow or gravel is that without ABS, locked wheels cause a build up of debris to form ahead of the locked wheel which effectively becomes a wedge and causes additional friction hence the shorter braking distance than a car equipped with ABS where the wheels continue to roll over any debris hence no wedge.

Who says that ABS equiped vehicles take longer to stop on snow? The only scientific study I have been able to locate for this subject the NTSA test referenced by wikipedia didn't do tests on either ice or snow, the nearest surface that would approximate this was wet grass and the results for that were not conclusive. I would also have reservations with respect to their tests on gravel which at 2 inches depth was closer to a sand drag then a normal loose gravel road surface.
While I can accept that on a gravel surface the nature of gravel forming a wedge under a locked wheel a plough in effect may give better braking than ABS I can't accept the same argument for snow the dynamics of which including the propensity to turn to water under pressure are very different and it doesn't tie in with my own observations.

I think that in some of the posts above there is a little confusion between ABS and ABD. Extensive research of real life collisions has shown that one of the strange things that regularly occurs just prior to impact is that the driver does not apply maximum braking just prior to impact despite it being obvious to the driver that they are about to suffer a serious or fatal injury. It is due to this fact that Brake Assist, ABD (Assisted brake distrubution) or whatever a manufacture wishes to call it was devised, this system senses the manner in which the brakes are applied and then applies maximum braking if the driver fails to do so. When first fitted to cars (IIRC Mercedes was the first) there was a tendency for the system to be "over active" with drivers complaining of the car doing emergency braking when not requested. With improvements in technology this issue has been resolved and just like car stability systems the newer the car the more effective they are in real life situations.

At work I drive high end high performance cars and the difference in the operation of the newer systems is quite significant, with the latest being very subtle and very effective.

One thing to bear in mind with ABS is that there is a large proportion of drivers who have never felt what happens with ABS when it is activated (the pedal juddering and bouncing up and down) which can frighten some drivers and cause them to release the brake pedal, another reason why ABD has been developed.

Yes I would agree with that it can be very alarming first time even if ready for it, I personally think that there is an increasing compelling argument to put drivers in a simulator as part of their training but I guess that would deserve a thread of it's own

cachaciero

Post by **myglaren** » 20 Dec 2009, 16:55

cachaciero wrote: Yes I would agree with that it can be very alarming first time even if ready for it, I personally think that there is an increasing compelling argument to put drivers in a simulator as part of their training but I guess that would deserve a thread of it's own

cachaciero

It certainly wouldn't be wrong to get learners onto a skidpan before they take their tests.

It would also be advantageous to revisit the skidpan fairly frequently to assess the characteristics of your current car and be at least somewhat prepared in the event of a skid.

bencowell · Post by **bencowell** » 20 Dec 2009, 18:11

myglaren wrote:It would also be advantageous to revisit the skidpan fairly frequently to assess the characteristics of your current car and be at least somewhat prepared in the event of a skid.

Back corner of Aldi car park on Saturday afternoon. Job done!

DickieG · Post by **DickieG** » 20 Dec 2009, 20:23

cachaciero wrote:
DickieG wrote:The correct reason behind and ABS equipped vehicle taking longer to stop on snow or gravel is that without ABS, locked wheels cause a build up of debris to form ahead of the locked wheel which effectively becomes a wedge and causes additional friction hence the shorter braking distance than a car equipped with ABS where the wheels continue to roll over any debris hence no wedge.
Who says that ABS equiped vehicles take longer to stop on snow?

The instructors training traffic police officers at Metropolitan Police Technical Training, a worldwide accredited establishment for the training of Police Officers in the investigation of collisions.

DickieG · Post by **DickieG** » 20 Dec 2009, 20:32

myglaren wrote:
cachaciero wrote: Yes I would agree with that it can be very alarming first time even if ready for it, I personally think that there is an increasing compelling argument to put drivers in a simulator as part of their training but I guess that would deserve a thread of it's own

cachaciero
It certainly wouldn't be wrong to get learners onto a skidpan before they take their tests.

It would also be advantageous to revisit the skidpan fairly frequently to assess the characteristics of your current car and be at least somewhat prepared in the event of a skid.

If you are driving a modern car equipped with DSC, ESP or whatever a manufacturer calls their car stability program, skid pan training is now redundant as those computers outperform drivers by a considerable margin whatever your skill/experience level just like the latest fighter jets that are unflyable by even the most skillful of test pilots if the computer stops working. These modern systems are so good that if a car is equipped with them and you still somehow manage to lose control of a car it doesn't matter whether you are Michael Schumacher there comes a point where physics takes over and you've now found it, prepare to say hello to the hedge, if you're "lucky".

Deanxm · Post by **Deanxm** » 20 Dec 2009, 20:45

Abs is ok but if you know the vehicle you drive well an emergency stop can be achieved without fully locking up, after a bit of practice it becomes second nature on dry roads, like knowing where your clutch bite point is.
To be honest though on ice and snow abs is rubbish and it would be nice to turn it off in the same way you can with T/C so the car starts with it on by default, on snow i find braking is best acheived by letting the wheels lock for a bit to dig into the snow then ease off to steer then lock them again, on ice i dont use the brakes anyway, just engine braking is all you really need untill your doing a couple of miles an hour and need to fully stop, shouldnt really use the brakes as you should be leaving enough space in front, driving much slower and planing more.
Saying this though the XM's abs is very good, its not up there with some of the newer high end manufacturers obviously but it isnt as intrusive as a lot of vehicles ive driven and keeps the wheels spinning slow enough to make the tyres squeel thus making them hot and sticky, giving maximum grip.
Our mazda company vehicle on the other hand has the worst abs i have ever had the misfortune of using, it seems like it will not let the wheels turn any slower than the average rotational speed of all 4 wheels, so the tyres dont heat up, when the abs cuts in its like you have taken your foot of the brakes its awefull.

D

deian · Post by **deian** » 20 Dec 2009, 21:29

Doesn't the ABS have a fuse? Pull it out if driving in snow, shove it back in when snow has cleared.

I haven't had the mispleasure of abs kicking the pedal back to me like in old cars, the xantia one is lovely, and i like to think of the hydraulic brakes as the brake assist, unless i have bubbles in my brake lines

I agree with Richard, we cannot defy Newtons laws yet, even with the best of help, I would assume you can quite easily crash any car if you drive it idiotically enough in the wrong conditions, but for most people even fast and careful drivers the electronic aids in the newest cars will save lives.

addo · Post by **addo** » 20 Dec 2009, 21:31

I'm not sure skid pan "training" is redundant; no amount of electronic fluff on a car (presuming all drivers can afford same) makes up for blind panic reactions.

One of the classics is people taking their hands off the steering wheel when they've sensed a loss of control.

Anyone else seen this happen?

Surely I'm not the only one who sees merit in getting people through this stage before it ever occurs in real life?

DickieG · Post by **DickieG** » 20 Dec 2009, 21:50

addo wrote:I'm not sure skid pan "training" is redundant; no amount of electronic fluff on a car (presuming all drivers can afford same) makes up for blind panic reactions.

One of the classics is people taking their hands off the steering wheel when they've sensed a loss of control. Anyone else seen this happen?

Surely I'm not the only one who sees merit in getting people through this stage before it ever occurs in real life?

The big issue with driving is that there is no accounting for stupid behaviour before, during or after an incident, the only answer is to observe, anticipate and plan your drive, failure to do that will result in trusting your reactions which are never as effective.

The latest stability control systems really are as good as you can hope for, provided you steer and brake in relation to whatever is happening ahead of you they give you the best chance of avoiding a collision for a situation that really is unexpected such as (for example) a vehicle not stopping at a crossroads stop line. However if your OAP is poor then nothing will save you and certainly not skid pan training as that is reactionary, its far better to concentrate on developing your OAP than to think about how much ("sexy") skid pan training can do for you.

Deanxm · Post by **Deanxm** » 20 Dec 2009, 21:52

YES! on the dual carrageway a woman in a daewoooo was in front of me on the inside lane, the mankiest looking mixi rabbit came out of a bush in front of her, she hitb the brakes and put both hands over her face................yes thats right!, we were doing 40ish so i went around her rather than slaming on the brakes and put the rabbit which had now made it into the outside lane out of its missery, sorry but i dont do emergency stops for animals unless there is no one behind in sight or its a bull elephant..............certainly dont let go of the wheel and cover my eyes either

D

Deanxm · Post by **Deanxm** » 20 Dec 2009, 22:19

and so far as skid pan training goes i think it IS a good idea in some ways, it would be nice for people to experience what happens when a car is pushed beyond its limits, for those who think they can drive it would wake them up to the fact that on the roads you dont have the space to risk allowing the vehicle to slide about in any way, controlled or not and for the daewoo woman above it may have given her the confidence behind the wheel she needed you would be surprised (or maybe not actualy) at how many people dont realise you loose steering control when the front wheels are locked which is very basic stuff.
On the whole though although im not a fan of driving aids most are a good idea, abs is a good idea i will admit, in that panic situation it does allow you to concentrate on steering the car without having to think about your brake application, T/C i dont really see the point in, i think what most people need is some throttle control, not traction control, stability control is probably a good thing too for those panic situations but i cant help thinking that all they do is allow some people to drive beyond their limits but more importantly think they can drive beyond what the road conditions allow.........

D

DickieG · Post by **DickieG** » 20 Dec 2009, 22:28

Deanxm wrote:T/C i dont really see the point in, i think what most people need is some throttle control, not traction control, stability control is probably a good thing too for those panic situations but i cant help thinking that all they do is allow some people to drive beyond their limits but more importantly think they can drive beyond what the road conditions allow.........

A very valid point which goes some way to explaining the behaviour of some 4 x 4 drivers, its well acknowledged that the biggest contribution to improving road safety would be to fit a bayonet to the steering wheel.

cachaciero · Post by **cachaciero** » 20 Dec 2009, 22:50

DickieG wrote:
cachaciero wrote:
DickieG wrote:The correct reason behind and ABS equipped vehicle taking longer to stop on snow or gravel is that without ABS, locked wheels cause a build up of debris to form ahead of the locked wheel which effectively becomes a wedge and causes additional friction hence the shorter braking distance than a car equipped with ABS where the wheels continue to roll over any debris hence no wedge.
Who says that ABS equiped vehicles take longer to stop on snow?
The instructors training traffic police officers at Metropolitan Police Technical Training, a worldwide accredited establishment for the training of Police Officers in the investigation of collisions.

Ha! the police now we all know how good they are at getting the right end of the stick

I wonder then how they would explain this? see http://www.stop.se/test/winter.htm and follow the link to download complete report..
which demonstrates quite conclusively that on a snow and ice test track braking with ABS out performed braking without ABS and this over a variety of tyre types.
Now to be fair these results are shown as deceleration values in G rather than absolute stopping distances but in my book more G equates to shorter stopping distances.
(worth reading the reference for other observations on ABS and safety issues )

Cachaciero

Kowalski · Post by **Kowalski** » 20 Dec 2009, 23:21

If you lock your wheels your car can be steered into a ditch by the road camber when there is ice on the road. Under those sorts of conditions, ABS is an advantage because it means you can brake. Locking your wheels and skidding could mean your car drives on the tarmac that isn't clear of slush or snow where it will take much longer to stop that on wet / icy tarmac.

My C5 has ESP and a button to turn it off if needed. In the summer I was trying to do a hill start with the ESP turned on, on a gravel road. The ESP applied brakes and cut power which resulted in my stalling three times. Turning the ESP off let me perform the hillstart with a very small amount of wheel slip. Turning the ESP off should put the ABS into some sort of slippery surface / snow / ice / gravel mode, whether or not it does is an entirely different matter.

DickieG · Post by **DickieG** » 21 Dec 2009, 00:15

cachaciero wrote:Ha! the police now we all know how good they are at getting the right end of the stick

I wonder then how they would explain this? see http://www.stop.se/test/winter.htm and follow the link to download complete report..
which demonstrates quite conclusively that on a snow and ice test track braking with ABS out performed braking without ABS and this over a variety of tyre types.
Now to be fair these results are shown as deceleration values in G rather than absolute stopping distances but in my book more G equates to shorter stopping distances.
(worth reading the reference for other observations on ABS and safety issues )

Cachaciero

Whilst you choose to mock the plod it may interest you to know that they do not make up the science, their training is certificated by independent bodies such as these who have far more expertise than I am prepared to contest.

The report you quote actually caused me to giggle when reading "Since a frozen lake lacks inclinations and is slightly concave, the braking tests were combined with a smooth lane change manoeuvre. Still, these tests may have been too easy for drivers to carry out, in comparison with emergency braking in real traffic on uneven, convex and inclined road surfaces. Therefore, more road-like surfaces were selected for the tests reported below"

Hmm, can anyone tell me what a "more road-like surface" is?

Questionable research I suggest, particularly when only one make and model of car is used and apparently not even on a road

As with all statistics we can all search long enough to prove any point of view, but would you honestly expect that document to stand up in a court of law?