[deetjohn]

Originally Posted by Neilguy

Here is a video which tries to explain how ABS works and how to use it to our advantage in real world situations:
safe braking with ABS by Bosch - YouTube

Great video there. Thanks Neilguy.

Now, in the video above, I see that almost all the drivers are pressing the clutch pedal while braking. Why are they doing it? Aren't we supposed to not touch the clutch pedal and use engine braking as well to slow down? I know Diesels don't offer much in terms of engine braking. But at least in a petrol car, aren't we supposed to 'use' engine braking while stopping?

Or is engine braking not advised in a ABS equipped car for some reason?

[antz.bin]

Originally Posted by honeybee

At the risk of digressing from the original topic, I must say the speed limits imposed in our country are because we aren't yet mature, as vehicle owners and also as drivers. While calling the speed limits downright absurd, you are conveniently forgetting that almost all the accidents which took place on the expressways could have very well been avoided (or at least become non-fatal) if the respective drivers had been abiding by the speed limits imposed. The speed limits aren't imposed by illiterate road workers. The government does take into account all the different vehicles which will ply onto the road and accordingly imposes the limits. To say these limits are absurd just because you happen to own a fast car is in fact absurd.

Perhaps in Pakistan they don't impose speed limits because they never know when a bomb will explode there. j/k

ABS or no ABS, if you followed the speed limits you wouldn't see so many accidents. That's a fact.

Respectfully disagree here. I believe most modern cars are stable enough to encounter most turns on the E-Way staying within even the Pakistani Speed limits. I almost drive at 100-105 on all dual carriageways (Speedo reads), on the bike or in a car. AND I am labelled by most as a sedate / steady driver. I do this because I don't feel safe while driving within the National Speed Limit. Too many vehicles whizzing by me on the road without me being in control is not my idea of a safe drive.

I cant say about you but I swear I wouldn't feel safe doing 35kmph in a Tata Indica driving in the middle lane of the E-Way even though it is perfectly legal to do so. I didn't mean to say that we need extreme minimum speed limits like those in Pakistan. But a sedate minimum speed limit of 60 and a max limit of 100 is not exactly 'unsafe'.

Anyways, if one wants to avoid accidents on the Highway, what one needs is not 'slow speeds'. One needs concentration, foresight and anticipation while driving. Knowing the limits of your vehicle as a driver also goes a long way in maintaining safety on the roads. Anyways, If you feel your car cannot safely do 100 constant on the E-way, you are better off taking the old NH4.

[Zed]

Originally Posted by deetjohn

Great video there. Thanks Neilguy.

Now, in the video above, I see that almost all the drivers are pressing the clutch pedal while braking. Why are they doing it? Aren't we supposed to not touch the clutch pedal and use engine braking as well to slow down? I know Diesels don't offer much in terms of engine braking. But at least in a petrol car, aren't we supposed to 'use' engine braking while stopping?

Or is engine braking not advised in a ABS equipped car for some reason?

You also need to down shift, to get the maximum effect of engine braking in tandem with ABS - hence the clutch pedal actuation in the videos. And as far as i know the car should not stall at the end of an emergency braking situation as per driving license tests.

[deetjohn]

Originally Posted by Zed

You also need to down shift, to get the maximum effect of engine braking in tandem with ABS - hence the clutch pedal actuation in the videos. And as far as i know the car should not stall at the end of an emergency braking situation as per driving license tests.

But then after down shifting, one would need to let go off the clutch for engine braking to occur and then press the clutch pedal again when the speed reduces and the engine is about to knock. However, I am not seeing that in this video.

[suhaas307]

Originally Posted by honeybee

At the risk of digressing from the original topic, I must say the speed limits imposed in our country are because we aren't yet mature, as vehicle owners and also as drivers. While calling the speed limits downright absurd, you are conveniently forgetting that almost all the accidents which took place on the expressways could have very well been avoided (or at least become non-fatal) if the respective drivers had been abiding by the speed limits imposed. The speed limits aren't imposed by illiterate road workers. The government does take into account all the different vehicles which will ply onto the road and accordingly imposes the limits. To say these limits are absurd just because you happen to own a fast car is in fact absurd.

Perhaps in Pakistan they don't impose speed limits because they never know when a bomb will explode there. j/k

ABS or no ABS, if you followed the speed limits you wouldn't see so many accidents. That's a fact.

Completely!

Originally Posted by antz.bin

Respectfully disagree here. I believe most modern cars are stable enough to encounter most turns on the E-Way staying within even the Pakistani Speed limits. I almost drive at 100-105 on all dual carriageways (Speedo reads), on the bike or in a car. AND I am labelled by most as a sedate / steady driver. I do this because I don't feel safe while driving within the National Speed Limit. Too many vehicles whizzing by me on the road without me being in control is not my idea of a safe drive.

I cant say about you but I swear I wouldn't feel safe doing 35kmph in a Tata Indica driving in the middle lane of the E-Way even though it is perfectly legal to do so. I didn't mean to say that we need extreme minimum speed limits like those in Pakistan. But a sedate minimum speed limit of 60 and a max limit of 100 is not exactly 'unsafe'.

Anyways, if one wants to avoid accidents on the Highway, what one needs is not 'slow speeds'. One needs concentration, foresight and anticipation while driving. Knowing the limits of your vehicle as a driver also goes a long way in maintaining safety on the roads. Anyways, If you feel your car cannot safely do 100 constant on the E-way, you are better off taking the old NH4.

There are speed limits for a reason.

As Honeybee had pointed out, there are a lot of things taken into consideration.

You see, Indian highways are very different from expressways and dual-carriageways you find in other countries. Not only will you have to keep your eyes peeled for broken-down trucks and idiots driving in the wrong lane, one must always watch out for stray cattle, animals, and even people sauntering across the road like it's their living-room. And then you have suicidal cyclists riding along the median and singing songs, completely oblivious to the fact that there are cars doing a good 120 km/h a mere 3 ft away from them.

Simply put, our roads are not meant for safe high-speed driving. Our roads aren't always completely flat. There are always undulations somewhere or the other that can throw you off guard. You'd always see some road-work going on. There are people driving little hatchbacks loaded with a weekend's worth of luggage and 5 people on board, and these very cars drive like they're in a city. They try and weave through highway traffic, and don't observe the highway code at all.

So why go through all that trouble and stay on the edge, melt your brain by concentrating extra hard while doing speeds like 140 km/h when one can save all that added pressure and cruise at 80 km/h and do an occasional 100 when you feel completely confident and sure of the road ahead?!

Follow the speed limit.

The moment people begin to follow rules, keep themselves informed, respect the highway codes and observe proper driving etiquette, accidents on the roads will reduce and the tarmac would be a better place.

[keyur]

Originally Posted by asr245

I had ABS kick in my City after I had to brake hard from a speed of 30-35kmph. I felt it kick in (on my feet) just before the vehicle came ot a halt

Try the same at 120 and you will feel the difference (both intensity and time duration).

Originally Posted by cranky

If he had been within limits ABS would not have even kicked in.

What's with you and the speed limits and ABS?
ABS kicks in when :
1. There is relative speed difference after braking
2. There is sudden deceleration due to braking (not gradual).

This has nothing to do with speed!

Originally Posted by moralfibre

Hey Keyur, first of all, great gesture of stopping by to help the victims. Just yesterday we had a thread on "The Good Samaritan" here.. You make an entry in there.

Hey moral, thanks for the suggestion, but I would like to refrain from that. I had posted my help sequence just as a description of the events in the order in which they happened - never even realized or expected it to be noticed - that's something which is expected of everyone, and I have done nothing great, so I will let it be at that.

Originally Posted by parik_ind

I am just trying to imagine what would have happened if this was a non ABS vehicle and the driver continued to stand on the brakes as he swerved.

I think the driver would probably have controlled it. The driver had been with the owner since quite some time and was experienced. I am not denying driver error in initiating the accident - but the sudden panic due to the ABS was not something his reflexes were trained to!

He probably would have pumped the brakes or turned in the direction of the skid.

Originally Posted by vnabhi

In the accident above, even in a non-ABS car it would have happened, as the driver would have lost control of the steering and perhaps hit the railing at a higher speed.

It appears both airbags were deployed. So if the owner had taken his seatbelt off, how did that one go off?

The airbags in the captiva deploy by themselves.

Originally Posted by carfreak77

Also, why in the world was he swerving at 120+ in a tall SUV.

I am very sure he was not doing it for fun. Even I have faced instances where you see (or you feel that you have seen) some obstacle / ditch / idiot on the road and suddenly do a stupid maneuver.

Originally Posted by arun_josie

What kind of test was it to get used to ABS? Can you please share?
For quite some time I am thinking to test ABS in my car but not sure on what kind of road, speed the test should be performed.

We did this testing on an open ground (stadium near where we stay). The ground has soil and gravel.
To test it, we drove at varying speeds, and braked (gradually to hard). The ABS kicking in does shudder much harder at higher speeds than at lower speeds - at 30-35, it will not create a panic - but at around 100, the feeling is prominent - heck, I was wary even after doing it 2-3 times.

But again, in nearly all cases, ABS kicked in when we braked hard suddenly, and hardly for the gradual braking. We even tried this in my non-ABS Optra on the same ground, and pumping the brakes worked fine enough.

I am not against ABS, but I bought my non-ABS vehicle strictly because I did not want ABS - I like the occasional drift, and braking is not an issue.

[quote=souravc;2506632
The tyres marks make it look like , it was being driven by one of those nut case drivers who try to overtake with all 4 beyond the yellow line demarcation on the expressway . [/quote]

The accident area goes much beyond the tyre marks - It starts from farther up. It was a bit confusing to draw the exact conclusions considering that the vehicle had hit BOTH the edges of the road!

Originally Posted by GTO

The driver's story is incomplete, and has too many loopholes.
In all likelihood, he was doing 140ish, and saw something at the nth moment (a car? a pedestrian? a rock?). Swerved + braked really hard to avoid impact, which led to a complete loss of control.

@ Keyur : You are a hero to stop, help and use first-aid on the injured. Thanks for setting an example for the rest of us.

I tried asking details, but I can't blame the driver for not realizing what exactly happened - he was completely shaken up. I am surprised that he remembered even as much!
I mentioned 120 because the owner had also said that they were at 120 or so and he had asked his driver to reduce the speed. I too reached the same conclusion that probably the driver saw something at the last moment and in the attempt to avoid it, panicked, braked hard and swerved, then panicked again and tumbled.

About the hero thing - I would respectfully disagree - there is nothing great about what I did, and it is just plain human. There were a few others too who did the same - never occurred to me to do otherwise.

[sydras]

I wonder if others have experienced this but in my inter-city trips I've often noticed Captiva owners to be the most serious offenders when it comes to speed. Maybe it's because of that insane amount of rubber hugging the road (Captiva tyres are really big and wide).

It's hard to believe that a vehicle such as this could topple so easily. The driver must have veered violently to the left and right to cause such an accident. Then again, SUVs are kind of notorious for toppling in the U.S. due to their high centre of gravity.

[prasadee]

Many years back I attended a training course called "Driving in adverse conditions". Not necessarily winter driving. It involved aggressive braking on slick surfaces (water, & sand). Objective is to understand the braking distance at different speeds in different conditions. Both weather and different tyre pressures.

Such a training course, would have been my own business idea in India. The main need would be a large parking lot or an air strip that I can rent out for a weekend, construction cones, and equipment to cleanup. Its just plain physics, but most people do not know of the limitations (of both man and machine) while cruizing.

Hopefully someone with enough resources will start such schools in most cities. People who upgrade to bigger powerful cars should get this from car makers, or get this on their own. Apart from knowledge gained about the potential of their cars, prevent accidents like these, it can also be a lot of fun.

[anilisanil]

Originally Posted by deetjohn

Now, in the video above, I see that almost all the drivers are pressing the clutch pedal while braking. Why are they doing it?

Probably to not to stall the car, while it is advisable to use engine braking to slow down, it is good idea to depress the clutch if you are braking to a halt to avoid stalling.

I know Diesels don't offer much in terms of engine braking.

How did you come to this conclusion? It is actually reverse, owing to high torque (same power delivered at low RPM) everything else remaining constant, a diesel engine should give out more engine braking than a similarly sized petrol engine.

Or is engine braking not advised in a ABS equipped car for some reason?

Engine braking is essentially taking your leg off the gas pedal while the tranny is still engaged. This means you are actually using vehicle's momentum (instead of fuel) to maintain the Engine RPM and hence it slows down your car (it is more like friction) and hence the word Engine braking.

So there is nothing in ABS that should effect Engine Braking.

[deetjohn]

Originally Posted by VeluM

Engine braking is Only to be used in regular driving situations, and not emergencies.

During an emergency, one's priority and focus will be on braking and avoiding the "obstacle", and trying to figure out when to clutch and de-clutch will do no good.

Also engine braking is only effective when the engine is turning at higher rpms. As the vehicle slows down, the engine will begin to provide motive force, detracting from the overall braking force being applied, which defeats the purpose.

In short, in emergencies - if the car has ABS, stand on both the clutch and brake pedals and concentrate on steering with gentle input to avoid the obstacle.

Thanks VeluM. That bit on motive force makes a lot of sense.

Originally Posted by anilisanil

Probably to not to stall the car, while it is advisable to use engine braking to slow down, it is good idea to depress the clutch if you are braking to a halt to avoid stalling.

Yes, this makes sense too. I guess the driver should be careful not to stall the engine at the last moment. Won't ABS stop working if the engine stalls?

Originally Posted by anilisanil

How did you come to this conclusion? It is actually reverse, owing to high torque (same power delivered at low RPM) everything else remaining constant, a diesel engine should give out more engine braking than a similarly sized petrol engine.

I could be wrong, but I have always felt that the petrol engine gives more engine braking than the modern high speed Diesels. I always use engine braking to slow down. Be it for a curve or a speed bump. Infact, I love to do it so much that I always come down a gear or two before braking. And, of course I am talking about planned braking here.

Now, imagine this scenario. I am doing about 50KMPH in 4th. If I see a sweeping curve ahead, I will naturally shift to 3rd before reaching it. Now, in a petrol the rpm will go up and the vehicle will feel under control. The car is in a very controlled and constant deceleration. Now, you touch the brakes to slow down further if required. And in some situations, one can manage without braking at all in a petrol.

And, imagine this same scenario with a Diesel. I am talking about a Swift Diesel here. When I shift to 3rd for the curve, I have always felt that the car is resisting to slow down as well as a petrol. For that instance when you de-clutch, the car will slow down a bit. But if you touch the brake without pressing the clutching pedal, the engine will try to resist the slowing down and pull the car forward, its more like coming into the torque band. So, I have felt the need to brake more with a Diesel than a petrol. Engine braking alone doesn't help.

Originally Posted by anilisanil

Engine braking is essentially taking your leg off the gas pedal while the tranny is still engaged. This means you are actually using vehicle's momentum (instead of fuel) to maintain the Engine RPM and hence it slows down your car (it is more like friction) and hence the word Engine braking.

So there is nothing in ABS that should effect Engine Braking.

Engine braking is not just friction. Read up on throttle vacuum here. Engine braking - Wikipedia, the free encyclopedia.

So if I understand this correctly, under panic braking, the whole point is to fully trust the ABS system, stand on the brake and clutch pedal, not let the engine stall and steer away to safety if required.

[suhaas307]

Originally Posted by deetjohn

Now, in the video above, I see that almost all the drivers are pressing the clutch pedal while braking. Why are they doing it? Aren't we supposed to not touch the clutch pedal and use engine braking as well to slow down? I know Diesels don't offer much in terms of engine braking. But at least in a petrol car, aren't we supposed to 'use' engine braking while stopping?

Or is engine braking not advised in a ABS equipped car for some reason?

Originally Posted by anilisanil

Probably to not to stall the car, while it is advisable to use engine braking to slow down, it is good idea to depress the clutch if you are braking to a halt to avoid stalling.

One must never depress the clutch while braking. This is a habit most drivers adopt. Pressing the clutch while braking, or pressing the clutch when one is not changing gear is a habit that is referred to as 'riding-the-clutch'. the life of the clutch considerably comes down if one rides the clutch on a regular basis.

The clutch must be depressed only when you're changing gear. One must keep their ears open and 'feel' the car's revs fall and only then attempt to change gear. Riding the clutch will not only reduce life of the clutch, it will not help the Fuel-Efficiency of the car.

One must depress the clutch completely while braking, only if you're braking hard and dropping your speed very quickly, in which case, the gear one must be in is a much lower one. Only when shedding lots of speed all of a sudden, must one depress the clutch while applying the brakes.

Engine braking has nothing to do with ABS. One can adopt engine-braking tactics whether the car is equipped with ABS or not. Engine braking is a good way of stopping the car, in fact. It helps you understand the spacing of the ratios. ABS will come into play when the brakes are slammed and the brakes lock up, not allowing free movement of the wheels and the brakes. What it does, is it negates the lock-up and allows one to regain control of the car, despite braking hard.

[anilisanil]

Originally Posted by deetjohn

And, imagine this same scenario with a Diesel. I am talking about a Swift Diesel here. When I shift to 3rd for the curve, I have always felt that the car is resisting to slow down as well as a petrol. For that instant when you de-clutch the car will slow down a bit but if you touch the brake without declutching, the engine will try to resist and pull the car forward, its more like coming into the torque band.

If you are in fourth gear and just below the turbo spool, when you change the gear you will come into the turbo range due to increase in RPM; turbo charges your vehicles and you feel the car accelerating. Which is why you felt so. You feel the same if you were driving a turbo charged petrol under similar conditions, this has got nothing to do with Diesels having lesser Engine Braking.

Just to make things clear: say a 1.4 L diesel produces X bhp at 3000 rpm and a 1.4 L petrol produces as X bhp at 5000 rpm so at the flywheel, which engines is producing more power per rpm? So if you take your leg off the gas pedal, which engine consumes more power from tranny per RPM? So which engine has more braking per RPM?

Engine braking is not just friction. Read up on throttle vacuum here. Engine braking - Wikipedia, the free encyclopedia.

Friction was used as an analogy, I did not and would never mean to say that Engine braking and friction are same.


Edit: Just read that link, now that confused me honestly. But any one can write in Wikipedia, just let me do a search and get back on this. Thanks for opening the debate though!!


Edit again: Here we go, I still think I am right and that Wiki entry requires to be corrected. Go through this thread http://www.4x4community.co.za/forum/...ad.php?t=50339

[simplyself]

Actually, touching the brake while slowing down is not bad altogether. It facilitates quicker down shifting. What many auto mags say is pointless. Engine braking is a measure of slowing down if the warning is very adavnced, I mean, if we detect something ahead very early then we can use engine braking. But I prefer getting into neutral immediately if I detect something ahead-e.g. take a speed breaker on a road - as it is immobile, I come into neutral and coast along for, say, about 20 metres, and by the time the rear tyres come off the breaker, I would rather be into appropriate gear. This is method I prefer.

The driver may be unaware of how the ABS works. The owner should have trained the driver properly. You cannot place blame squarely on the hapless driver who may not have driven a vehicle with ABS earlier.

[deetjohn]

Originally Posted by suhaas307

One must depress the clutch completely while braking, only if you're braking hard and dropping your speed very quickly, in which case, the gear one must be in is a much lower one. Only when shedding lots of speed all of a sudden, must one depress the clutch while applying the brakes.

Yes, everyone knows about planned braking. But I am trying to find out more about emergency braking in ABS equipped cars. And so far, what comes out is that it makes sense to stand on both clutch and brake.

Originally Posted by anilisanil

If you are in fourth gear and just below the turbo spool, when you change the gear you will come into the turbo range due to increase in RPM; turbo charges your vehicles and you feel the car accelerating. Which is why you felt so. You feel the same if you were driving a turbo charged petrol under similar conditions, this has got nothing to do with Diesels having lesser Engine Braking.

I have never driven a Turbo petrol. Would love to understand how different it behaves as compared to a NA petrol under engine braking.

Originally Posted by anilisanil

Edit: Just read that link, now that confused me honestly. But any one can write in Wikipedia, just let me do a search and get back on this. Thanks for opening the debate though!!

All the best and keep us posted. I have read about this in many articles and it makes sense. Because one controls air and not fuel with the throttle in a petrol car unlike a Diesel.

Edit: Actually, Throttle (verb) means Reduce the air supply, Kill by squeezing the throat of so as to cut off the air.

[vnabhi]

Originally Posted by anilisanil

If the car has seat belt pre-tensioner and a transducer connected to the air-bag circuit then and only then would the air-bags deploy only when the seat belt is buckled.

If there is no pretensioner, then air-bags deploy independently and are not interlinked to buckling.
.

That is exactly what the Hyundai service guys stated, when the car (Sonata) was given for repair. But the driver insists that he was not wearing a seatbelt.

In any case, both airbags and seat-belts had to be replaced.

I wonder who is correct.