[Jeroen]

I think a lot of us are picking a preferred option without us having really understood the underlying data pertaining to ABS and airbags and thus each respective effect on reducing fatalities.

Rationally You could argue that if you would have the choice (many of us have said they want both of course), I believe you would need to study accident rates. In a simple form, how many fatal accident have been prevented by ABS and how many fatalities have been prevented by airbags. Im using fatal accidents here, for simplicity and because I think it is the most relevant type of accident in this discussion.

Im not even sure if real data exist on how many fatal accidents have been prevented by ABS. Reading through the various replies I cant help but get the impression that a lot of members believe ABs provides better stopping distance. That is actually not true and a few posts have been made to this effect. although in practice it might give you a bit of edge, the most important aspect of ABS is that it allows you to control the car during emergency braking, on all sort of surfaces.

Again, I don't know the statistics in order to make a rational call on what would statistically reduce my change of dying in a car accident, ABS or airbags. Going by gut feeling I would tend to go for the airbag. Why? Again i don't have data to support but my impression is that when looking a various accidents, the ones I see on the roads, on youtube, hearing from friends, Im not convinced that braking or steerage was such a big factor. Also, as pointed out, the real advantage of ABS is providing steerage under emergency braking. That means that in an emergency you not only have to brake, but also steer! As pointed out, most drivers don't.Of course, many of us believe to be way better then average driver. Now statistically that is definitely not true, men vastly overrate their own driving skills.

Jeroen

[batterylow]

Originally Posted by Jeroen

Reading through the various replies I cant help but get the impression that a lot of members believe ABs provides better stopping distance. That is actually not true and a few posts have been made to this effect. although in practice it might give you a bit of edge, the most important aspect of ABS is that it allows you to control the car during emergency braking, on all sort of surfaces.


Jeroen

ABS does enable better stopping performance so that must equate to a lower braking distance right? Maybe that difference is braking distance might prove to be the difference between a fatal and a minor accident. My impression was that a wheel that is rotating can theoretically provide better braking than a wheel that is locked. Unless of course we are talking about loose surfaces where the material build up in front of a locked wheel can aid braking distances.

Regards,
BL

[IshaanIan]

Originally Posted by batterylow

ABS does enable better stopping performance so that must equate to a lower braking distance right? Maybe that difference is braking distance might prove to be the difference between a fatal and a minor accident.
Regards,
BL

Nope. On a dry track, a car without abs has a shorter braking distance. ABS aids in better braking in uncertain track/road conditions and allows you to control the car easier; steer and brake at the same time.

[batterylow]

Originally Posted by IshaanIan

Nope. On a dry track, a car without abs has a shorter braking distance. ABS aids in better braking in uncertain track/road conditions and allows you to control the car easier; steer and brake at the same time.

Lets consider a case scenario. 2 identical cars,one with ABS, one without

Case 1: Dry track with no slipping of the tyres.

In this case both the cars would have the same stopping distance right?
ABS comes into action only if the wheel speed sensors detect slip.

Case 2: Wet track with low friction

In this case the car without ABS would lock its wheels and slide further than the car with ABS which would be able to stop sooner.

This is my understanding of how ABS helps to reduce stopping distance.

Or am I missing something.

Regards,
BL

[Jeroen]

Originally Posted by batterylow

ABS does enable better stopping performance so that must equate to a lower braking distance right? Maybe that difference is braking distance might prove to be the difference between a fatal and a minor accident. My impression was that a wheel that is rotating can theoretically provide better braking than a wheel that is locked. Unless of course we are talking about loose surfaces where the material build up in front of a locked wheel can aid braking distances.

Not necessarily better stopping performance. On the difference between a fatal and a minor accident, see below.

Actually on a dry surface most wheel/tires give the best braking performance with a very light slip. That is difficult to measure, so ABS more or less goes from 100% block to release and 100% block again. And indeed on loose surfaces ABS might provide poorer performance then conventional brakes that simply lock up and create a lot of material build up in front of the tire.

Originally Posted by IshaanIan

Nope. On a dry track, a car without abs has a shorter braking distance. ABS aids in better braking in uncertain track/road conditions and allows you to control the car easier; steer and brake at the same time.

The important aspect of ABS is the ability to steer and brake at the same time, not the shorter stopping distance. Have a look at this thread that says it all:

http://www.team-bhp.com/forum/techni...ml#post3436436

Even the sales people get it wrong!

to me earlier point, very few people on this forum that have choosen ABS as their preferred option really understand what ABS would do. As I pointed out, we even lack any data that would give us an understanding of how many fatalities ABS has prevented. But we can drill into this some more and try to figure out for ourselves how usefull ABS really is.

I don't know about India, but in Europe and the USA the vast majority of fatal accidents happens at relative low speeds, ie below 80km/h. Accidents at high speeds are very few.

Look at the below table:

Below 80 km/h you will notice that a relatively large part of the total stopping distance is related to thinking (i.e. driver response time). With or without ABS that is not going to make any difference.

Now have look at these simple brake distance calculations:

http://en.wikipedia.org/wiki/Braking_distance

What is relevant that in order for a car to stop the total kinetic energy must be disipated by the brakes. Essentially, the cars kinetic energy gets converted into heating the brakes. As you can see in all the formulaes, speed is a big factor and often weighs in at the power 2. However, the way your brakes work (i.e. dissipate energy) is more linear. What does it mean, well on any given braking distance your car will decelerate quicker towards the end of the stopping distance. Or lets illustrate with a random example.
Say your stopping distance is 40 meter (real stopping distance, so excluding driver response time). Say for arguments sake it takes 4 seconds. Roughly speaking the first 2 seconds will see you eat up 30 meters and the next 2 seconds will bring you to a full stop in the last 10 meters. Dont quote me on the exact numbers its more to illustrate the principle.

So even if ABS does reduce braking distance, which in most cases might not be the case, it is highly debatable what the benefits would be. Say ABS reduces the braking distance by 10%, that brings the 40 meter back to 36 meters, but as you will appreciate after the same initial 2 seconds the speed of the car would still be relatively high and still a relativly large distance would have been covered.

Long story short/summary;

We dont' have any statistics that show us how effective ABS is in preventing fatalities. Simply no data available, would be great if anybody has seen or has access to this data.

Hopefully members are now beginning to understand what ABS really does, which is to allow steerage under emergency braking on multiple surfaces. So it more about "avoidance" then reducing stopping distance per se

99.999% of drivers, in particular men, overrate their driving skills by a huge margin. So I for one am not convinced that in an emergency situation most drivers will do more than only stomp on the brakes and also steer around whatever the obstacle is.

I like ABS for the sheer simplicity it brings to emergency braking, and the additional bonus of being able to steer whilst stomping on the brake. Whether I would actually steer remains to be seen. But if push comes to shove, and I would have to choose between ABS and airbag I would go for the airbag any day.

By the way, an airbag without the use of proper three point seatbelts is pretty useless, so always put your belt on.

Maybe we should redo the poll" See if any education and knowledge transfer has taken place?

Jeroen

[batterylow]

True.

ABS also helps prevent the resultant loss of control when a vehicle skids and swerves.

And it is true that the instinct of people is to brake when faced with an obstacle and maybe not steer away from it.

Regards,
BL

[DerAlte]

Originally Posted by Jeroen

... And indeed on loose surfaces ABS might provide poorer performance then conventional brakes that simply lock up and create a lot of material build up in front of the tire. ...

'Old wives tales', or speculative inferences. Controlled & instrumented track testing data from any ABS manufacturer (Bosch, Denso, Wabco, etc.) says otherwise.

And no, "material build up in front of the tire" doesn't contribute to better braking performance - the momentum will make the tyre ride over any build-up. One will need material build-up roughly 1/3 the dia of the tyre for significant resistance to 'riding over' (will happen only with deep-enough sand or snow, which is abnormal road conditions). Had it not been so, a 1-3" stone or pothole would stop the car's slide - it doesn't, the car just rides over it.

'it more about "avoidance" then reducing stopping distance per se' - absolutely correct. Vehicle controllability is more important than absolute distances. If vehicle is controllable, and driver has 'presence of mind', the driver can swerve / steer to safety instead of leaving it to fate (and physics).

[Jeroen]

Originally Posted by DerAlte

'Old wives tales', or speculative inferences. Controlled & instrumented track testing data from any ABS manufacturer (Bosch, Denso, Wabco, etc.) says otherwise.

Thanks, at least we do agree on what ABS is good for.

On the matter of ABS effectiveness on loose and slippery roads there are an anwfull lot of these 'old wives tales' out there.

This one for instance, from a safety institute.

http://www.sdt.com.au/safedrive-directory-ABSBRAKES.htm

I might be wrong but I thought that on real slippery surfaces ABS is not likely to work well? If that is true, going from a perfect dry surface to a completely iced up surface there is somewhere along where the ABS begins to falter. Is that true, and if so, what are the (road) conditions at which ABS begins to falter (if any).

I also came across this bit of interesting text. At long last there seems to be some data on the usefullness of ABS:

In February of this year (1996) the National Highway Traffic Safety Administration announced it had dropped the federal safety standard requirement for anti-lock brake systems on all new cars.

They did so because studies showed a 0% decrease in the overall number of accidents when comparing ABS equipped cars against those without ABS, AND because these studies showed a 40% increase in single vehicle run-off-the-road accidents with ABS equipped cars. (Apparently your odds of getting into an accident if you lock your brakes in a car is less than if you do not - implying that if you lock them you will likely simply slide in the direction you were moving, but if you maintain some measure of (impaired) control you are likely to throw the vehicle into a path that takes you off the road.)

The above point of view seems to correlate remarkably well with my suggestion that we tend to overrate our driver skills in a huge way.

Jeroen

Jeroen

[batterylow]

Originally Posted by Jeroen

I also came across this bit of interesting text. At long last there seems to be some data on the usefullness of ABS:


Jeroen

I think the increase or constancy of the accident rate in cars fitted with ABS can be attributed to the carelessness of the people disregarding safe braking distances expecting ABS to make up for the lack of time/distance.

[DerAlte]

Originally Posted by Jeroen

... I thought that on real slippery surfaces ABS is not likely to work well? If that is true, going from a perfect dry surface to a completely iced up surface there is somewhere along where the ABS begins to falter. Is that true, and if so, what are the (road) conditions at which ABS begins to falter (if any). ...

Incorrect attribution of culpability!

* Braking is proportional to µ - the coeff of friction - between the rubber tyre and the road surface. 'Slippery' = low µ, for example pure ice, or water on ceramic tiles, has µ close to 0

* ABS serves to prevent 'wheel locking' while braking, as it's name implies

* ABS doesn't control braking distances. Whatever braking distance is achieved, is proportional to µ

* ABS operation is independent of µ. ABS ECU only looks at the deceleration pattern of a wheel

Why then would one accuse ABS of not working in some circumstances? There aren't any! The only exclusions to ABS operation are very low and very high angular (rotational, not translational) deceleration of a wheel - it doesn't at all relate to the vehicle's speed (translational speed).

The incorrect attribution is related with braking of the vehicle. That is related to the µ of the surface with which the tyre is making contact (bad luck if one encounters black ice, e.g.), and the normal force exerted by the brake pads on the brake disk / drum (that is, how good are the *brakes* intrinsically). ABS system testers first test the intrinsic ability of the brakes of a car *before* testing a car for ABS.

Originally Posted by Jeroen

... I also came across this bit of interesting text. At long last there seems to be some data on the usefulness of ABS ...

Those were early days of commercial OE ABS. And one can't do anything about the sensibility, alertness and presence of mind of a driver, can they? Neither then, nor now. ABS is unrelated to 'Duh!' moments / drivers.

[Jeroen]

Originally Posted by batterylow

I think the increase or constancy of the accident rate in cars fitted with ABS can be attributed to the carelessness of the people disregarding safe braking distances expecting ABS to make up for the lack of time/distance.

Yes, too true. There is some evidence that ABS and all other safety measures, including airbags give drivers a hightened sense of "safety/protection" and therefor they start taking bigger risk, driving faster, closer etc

I can tell you from own experience you drive a Citroen 2CV differently compared to say a Mercedes 500. Not just because of the obvious difference in power and capabilities, but because you feel very vulnerable in a 2CV in modern traffic. Having said that, I get the impression that in India this doesnt work like that, everybody from pedestrian, TukTuk, bike, car, truck, bus driver takes to the road as if completley and utterly invincible. I kid you not, when I go out on my bullet I am by a very large margin, the most cautious, most apprensive drive on any Indian road. Just because I feel extremely vulnerable.

Originally Posted by DerAlte

Why then would one accuse ABS of not working in some circumstances? There aren't any! The only exclusions to ABS operation are very low and very high angular (rotational, not translational) deceleration of a wheel - it doesn't at all relate to the vehicle's speed (translational speed).

Ok, that means if say you are braking with the ABS working and you hit a patch of ice, that could be a problem as it might cause high deceleration?

Mind you, I'm not sure if you're better of hitting patches of ice with regular braking. Some years ago I was part of a team that took a couple of rag top sportscar to the polar circle in March, top down. We had proper wintertires with spikes, but when you hit dark ice, nothing slows you down, its pot luck, pray to God and hope you stay on the road, crash into someting soft, like a snow mountain.

[batterylow]

Originally Posted by Jeroen

Some years ago I was part of a team that took a couple of rag top sportscar to the polar circle in March, top down. We had proper wintertires with spikes, but when you hit dark ice, nothing slows you down, its pot luck, pray to God and hope you stay on the road, crash into someting soft, like a snow mountain.

Tell us about it, sounds like a good read from the look of it.

[DerAlte]

Originally Posted by Jeroen

... everybody from pedestrian, TukTuk, bike, car, truck, bus driver takes to the road as if completley and utterly invincible. I kid you not, when I go out on my bullet I am by a very large margin, the most cautious, most apprensive drive on any Indian road. ...

No, 'invincible' is an incorrect expectation. You see, the driving philosophy in India (and the sub-continent) is completely different. One walks and drives a vehicle in a pattern that is dictated by the 'next available space to fit'. One is lucky if one gets this pattern in a straight line, else one doesn't complain about it - one just meanders looking for that elusive 'next available space'.

Indians are not given to complaining about others not doing the right thing or not - they just 'do it'. Most, that is. Exceptions: (there are many) people like me who have been exposed to the rule-abiding, don't-impede-others-on-the-road driving philosophy in Europe and US, for whom it causes anger and ill-will towards people who don't do that. Driving schools in India teach one how to control the vehicle, not one should expect a specific predictable behavior. Just so that one adapts to the system of looking for 'next available space', rather than wishing / causing harm to others - we are non-violent, you see.

You are apprehensive, you are using your mind - they DON'T.

Originally Posted by Jeroen

... Ok, that means if say you are braking with the ABS working and you hit a patch of ice, that could be a problem as it might cause high deceleration? ...

No. High deceleration as in the wheel jamming which stops the wheel (rot speed = 0) in a few 10s of milliseconds. Also, only one wheel showing anomalous high deceleration behavior as compared to other wheels. In other conditions, the rotational deceleration is less, even on ice.

[sourabhzen]

I voted for ABS. I have faced situations a number of times when I wish I had ABS equipped car. As many of you have pointed out prevention is better than meeting an accident. My next car will have both though.

Pardon my ignorance, but I can not remember any car with Airbags and not having the ABS.

[batterylow]

Moderator note: Back to back posts, use Multi Quote [Quote +] instead Thanks.

Originally Posted by DerAlte

No, 'invincible' is an incorrect expectation. You see, the driving philosophy in India (and the sub-continent) is completely different. One walks and drives a vehicle in a pattern that is dictated by the 'next available space to fit'. One is lucky if one gets this pattern in a straight line, else one doesn't complain about it - one just meanders looking for that elusive 'next available space'.

Google for "Driving+india+coen+jukens"

It is a hilarious account by a foreigner from the Netherlands trying to make sense of the traffic flux that is the road in India.

Regards,
BL

Originally Posted by sourabhzen

I voted for ABS. I have faced situations a number of times when I wish I had ABS equipped car. As many of you have pointed out prevention is better than meeting an accident. My next car will have both though.

Pardon my ignorance, but I can not remember any car with Airbags and not having the ABS.

off the top of my head, the latest polo has only air bags in the lower variants.

Regards,
BL