speedking

Following a Boxster down the lanes in my MY02, went round a sharpish right hander which turned into a sheet of ice. About 40m ahead a Punto had slid off the road, bounced off a tree and ended up at right angles across the lane, completely blocking it. Two cars had stopped because they couldn't get past. The Porsche anchored up and slid to the left, I braked hard and steered right, he bounced off the bank (very low) and crossed back to end up across the road facing the right. I steered left and pushed harder on the middle pedal As anyone who has slid towards the side of a Boxster will testify, I was thinking "this is going to be expensive". But, the ABS enabled me to keep control and stop before impact

I reversed up the lane with hazards flashing to warn others, and I believe saved a TT (and the Porsche) from an untimely end.

Presumably it would have been my fault if I'd made contact

I've been totally underwhelmed by the ABS on bumpy approaches to junctions where it cuts in far too early. But in this situation the 4 channel feature undoubtedly helped to prevent an accident. Perhaps I could have stopped in a shorter distance by cadence braking, but I doubt it would have been so controlled, and a straight line stop would have been useless.

BTW the thermometer was registering +2°C. Be careful out there!

Mick

iTrader: (1)

Timely warning! - I would have loved a picture of the guy in the boxsters face as you came sliding towards him

Mick

ALi-B

iTrader: (1)

I hate to be the one pointing this out - but wern't all the cars you pointed out driving too fast for the conditions?

Ice can deveolop below +5 degrees C (which is why my Dad's beamer bleeps to tell me - I have no such luxury ) Obviously another example of drivers not using their common sense if you ask me

[Edited by ALi-B - 12/18/2003 11:39:30 AM]

speedking

ALi-B, it's a good point that you make, but only one vehicle crashed, so the others were driving at the perfect speed for the conditions

The 'safe' speed for this particular piece of ice would be about 5mph. Do you drive everywhere at 5mph if the temperature drops below 5°C? Thought not.

In these conditions I do throttle and brake tests to determine the likely slipperiness of the surface; this patch obviously caught everyone unawares.

ALi-B

iTrader: (1)

Well round the lanes (presuming you meant country lanes) I would be on the side of caution -Especially on bends. Without knowing the road I can't comment on a suitable speed in that particular circumstance.

But yes, if icy on a country lanes, I wouldn't be going much faster than 5mph round bends. Obviously on gritted A roads, I do drive alot faster - unless the council have cut the budget on gritting again

[Edited by ALi-B - 12/18/2003 12:14:28 PM]

OllyK

Think this is a pertinent point:

Always ensure that you can stop comfortably, on your own side of the road, within the distance that you know to be clear and will remain clear. Theer is also a special case on narrow roads where you should be able to stop in HALF the distance that you know to be clear to account for muppets coming the other way.

And from your own admission:
So there were 2 vehicles that crashed, the punto and the porker.

And
Yup - see original statement above!

Fortunately you didn't crash, but you were in a panic breaking situation. Suggests to me:
1) Increase the distance between you and the vehicle in front, and double it in the wet and treble it in icy conditions.
2) Be aware of the conditions
3) Slow down more on bends when you know there are adverse conditions; rain, cold, country lanes with possible mud on them.

OK - egg sucking lesson over , just glad everyone was OK!



[Edited by OllyK - 12/18/2003 12:19:35 PM]

John P

Speedking
Glad you held it together and had the presence of mind to reverse back to warn others. Just think if you had saved it hitting the Porsche and then while reversing had a TT go into the back of you and that really would have been interesting to explain on the insurance.
Shave the first two cars didnt try to warn others.
Sort of agree with Olly though that speeds and awareness have to be really thought about, not lecturing but as another thread says always think way ahead i.e. Think what if !!!! when I go round this corner there is a problem. Can I stop or what could I possibly do to avoid any trouble

lmsbman

Just a word of warning. ABS is designed to enable you to steer when braking heavily. A car without ABS will lock up and you will just skid in a straight line. ABS does not make you stop in a shorter distance, but it allows you to steer around the hazard. No doubt Mr Porsche had ABS fitted as well, so you can see that he still didn't have sufficient time to steer correctly.
So don't think you can go hammering along narrow country lanes and be able to stop. You still need to have room to steer around the hazard.
As far as cadence braking is concerned, you will be suprised at how cr*p that is compared to ABS. ABS locks/releases/locks etc about 10 faster than you could possibly do yourself.
In case you think I'm talking bollo*ks, I am a qualified instructor on Skid Car. Take a course at your local training venue and you will see what I mean, as well as having a bl**dy good laugh!

22b_or_not_22b

whats the point in owning these cars then if the max speed limit is only 70mph...... I know people were doing 70mph in this circumstance but surely you have to do the time if you commit the crime........

so if you are prepared to drive fast on public roads and have an accident you had the choice to slow down also.

and yes i dont drive slow.... just have fully comp insurance

Jiggerypokery

Eh?
70mph "down the lanes"? Wrong thread perhaps?

As speedking has already said, you can't drive everywhere at 5mph when the temp is less than 5 degrees. Try doing that round the lanes and you'll end up with a landrover in your boot.

Allan

iTrader: (1)

Imsbman,
Not sure I understand that, on a dry road I was under the impression it does help in reducing stopping distance, certainly for emergency braking.

ABS and the subsequent ability to continue to steer requires "GRIP" to work, therefore on ice it's useless.

Allan

[Edited by AllanP - 12/18/2003 1:08:49 PM]

SJ_Skyline

Back on topic -

speedking, looks like you had a lucky escape mate!

Take it easy out there guys!

Rich

Scooby Snacks 23

I don't have ABS on my Type R

speedking

FYI I would estimate that our speed was about 30mph, but TBH I wasn't watching the speedo Although narrow enough to not have a centre white line 2 cars can pass comfortably on this lane without slowing in normal circumstances, even at night.

OllyK 1st para. is correct. But I wasn't classing a no damage impact with a verge as a crash. LOL @ 'your own admission'. I didn't panic. I stopped in the space available, despite the fact that the Porsche was going sideways and I was under controlled braking.

Triggered an interesting discussion here about whether a car going sideways will stop quicker than a car travelling forwards with full ABS applied.

lmsbman: I thought that the optimum braking point was just before the wheel locked, and that because ABS cycles past this point many times you will stop quicker than a car which is skidding?

I went on a skid control course and it opened my eyes to how capable my 205 was on a diesel soaked surface. Possibly the opposite of the intended effect Learnt a lot though.

@22b I think you're on the wrong thread mate? Writing stuff like 'I know people were doing 70mph' which you then don't proofread is plain daft. BTW fully comp. insurance won't stop you getting injured

John P

Unfortunately AllanP the comment is correct. ABS only allows you to in effect steer and direct the car under severe braking. Although when the right foot is planted I have mostly held on for grim death and prayed I stopped in time and didn't have the thought of mind to actually steer the damn thing

MGJohn

Yes, it's that time of year again. Surprised by some of the comments on this thread. Gizzmos, Comprehensive Insurance ... these are considered life savers??? Yeah, right, stands to reason, so lets press on .... and I thought that old Volvo mentality was dead .....

There's only one really necessary safety device that should be fitted to all moving cars. That's a top quality nut holding the steering wheel!!

CataIunya

Thats not strictly true about ABS when your wheels lock you have lost grip, the point at which you have most braking force is at the point just before the wheels lock. So ABS pulses you between locked and not locked to get the most grip AND aid turning, in icy conditions your car can actually speed up on ice if you lock up, in snow its slightly different in that the compacted snow in fron of the wheel can help you slow down but then we start getting technical.

lmsbman

Without getting too technical, the ability to stop depends on the co-efficient of friction between the tyre and road surface.
A dry road in a good state of repair has a Mu value of about 0.75. An icy road is going to be much lower and if it is a flat sheet of ice could be near to zero. However, if it was zero, then you would never stop!!
Believe it or not, the shortest distance to stop on a dry road requires the brakes/wheels to be locked, as you need friction to stop. Unfortunately, when this occurs, you have no control over the car. The idea of ABS is to give you some degree of control over the car whilst still braking as hard as you can. ABS only works properly if you literally "stand on the brakes" and maintain that pressure untill you have stopped.
So if you can see where I am coming from, then you will realise that this is not an optimum situation to be in. If you have to use ABS then basically you were going too fast for the road/ traffic conditions. If you drive along anticipating hazards then hopefully you will never have to use it.
When braking on ice you are basically in the lap of the gods. There are numerous other factors that can effect whether the car can be controlled, such as camber of the road, suspension, one wheel locking before the other etc. The only safe way to brake on ice, is to do it very gently when you are travelling in a straight line. If it is possible, try to avoid braking, harsh acceleration/decelertaion or steering when on ice because any of these actions will upset the equilibrium of the car and has the potential to send you into a skid.

SiPie

Imsbman

Whilst I agree 99.9% with the above situations do arise when that just ain't the case. ie. Deer leaps over a hedge right in front of your car ... yup happened to me and there wasn't alot of anticipating to be done there

Same happened years ago when a bulldog ran right in front of my car...... through a gap in a hedge

Must be hedges..... <mental note to self> beware of hedges

Cheers
Si


[Edited by SiPie - 12/18/2003 2:10:57 PM]

Jiggerypokery

[pedantic mode] Oh yes you would! (panto season).
A WRX is travelling at 30MPH down a country lane and suddenly drives over a section of magic black ice with a frictional coefficient of zero. Given that the WRX has a drag coefficient of 0.33, how long will the WRX travel before coming to rest?
You may assume the following:
Air temp = +2 degrees celcius. Atmospheric pressure = 101325kPa. Altitude = 100m above sea level. Weight of the car = 1390kg.
[/pedantic mode]

[Edited by Jiggerypokery - 12/18/2003 2:44:26 PM]

Chris L

lmsbman makes some very good points here. I wonder how many people on here have actually been taught how to use ABS properly?

I did a day with Subaru and Top Gear a couple of years back. We spent a fair bit of time learning how to use ABS. It is a real eye opener to see how effective it is when it is used properly. It also requires a fair degree of control and nerve.

The test was conducted at about 60 miles an hour and simulated a motorway where a large object had fallen off a lorry and you were required to avoid the object and maintain control of the car. We were taught to hit the brake hard and then wait for 2 seconds (that's the scary bit) to allow the weight of the car to even out and then steer around the object. It bloody works! The problem with immeadiately braking and steering is that the car is very unbalanced because braking hard throws the weight of the car forward, making it difficult to control.

Question is would I have known this if I had not had the training and would I be confident in using it? No and I would now! Granted it is not always possible to use it like this, but I can't help feeling that ABS is one of those things that nearly everyone has, but it is more by luck than judgement if it actually works and saves someone!

Chris

Allan

iTrader: (1)

Chris very true, personally I'm not disputing how ABS should be used or what it does, I am however very surprised to learn that you will stop quicker with your wheels locked.

Allan

TopBanana

ABS is for gays

lmsbman

Oh no you wouldn't. If the mu is zero there is no friction. Without any friction the car won't stop. Vice versa it wouldn't start to move either, (mind you you wouldn't be able to get into the car anyway coz it would be impossible to walk as well!)

OllyK

lmsbman - granted your point on not being able to start. But assuming you were moving on normal tarmac and then hit the 0 Mu stuff, the wind resistance of the car body against the atmosphere would eventually stop the car, would take a bloody long time, but it would stop eventually. Now if we are in a vacuum, that's a different story!

Mind you, the car would not start, but reckon a human could. Lift one leg vertically and fall forwards, catching yourself on the raised leg when you have fallen forward a few inches. Personally wouldn't like to try as you would need bloody good balance and reactions, but it would get you moving forwards, even if it was on your face!

[Edited by OllyK - 12/18/2003 4:44:42 PM]

johnfelstead

I disagree that having the tyres locked stops you fastest. The grip of the tyre when locked decreases for lots of reasons, one of which is the molecular struture of the material will deteriorate in that localised area and reduce Mu as a consequence. The most grip is atained at the threshold of lock, as soon as you lock the wheels you reduce this.

Also in low grip conditions, ABS is a hindrence to retardation rates with a skilled driver at the wheel, unfortunately 99% of the population never gets trained in how to drive, they learn how to pass a driving test, so they are not equipped with the knowledge or skills required to make full use of a non ABS equipped car.

4 chanel ABS is a good adition to a car for Mr average, but in conditions like ice and snow it can destroy the cars ability to stop, If you rely on it your going to get a shock.

Just a moot point but the speed limit is 60MPH max on a road that isnt a dual carriageway, not 70MPH as suggested earlier.

lmsbman

Having spent a lot of time on an airfield doing skid tests I have found that on a dry surface there is hardly any difference in overall stopping distance between ABS and non ABS cars, although non abs cars stop generally in a shorter distance (albeit by an insignificant amount) This is done by standing on the brakes and keeping the pressure on untill you stop (not something most motorists will ever do, because they will normally reduce pressure once they start to skid)
I am not denouncing ABS, I think it is a brilliant bit of kit if you ever find yourself in an emergency situation. All I am saying is that drivers should not think it is going to make them stop much shorter, because it wont. It will allow you to steer but you need to have quick reactions.
It can have a detrimental effect on loose surfaces i.e. increse stopping distances. However, it will still enable you to steer.

To sum up what I am saying, drive according to the conditions. ABS is a tool but not the panacea to all ills.

yhe chod

heres a rant ..... people should take responsibility for their driving not relying on other drivers to compensate for their shoddy driving. dont be a sheep- always look ahead to antisipate,indicate what your trying to do and just lift your foot off the accelarater to slow rather than stamp your brakes every half minute. timing is the key sir.[im not saying there was any shoddy driving on the above incident]glad no one was hurt.meery xmas

[Edited by yhe chod - 12/18/2003 6:28:11 PM]

homer lawtey

Exactly, sounds like excelent driving to me. You're following a car around a corner when you hit ice just before an accident. The car infront slams on and looses control, narrowly avoiding a crash. You still managed to stop not only before the crash, but also avoiding the car in front who had just lost control.

Well done, change your under pants for clean ones, and go drink to your driving abilities.

CataIunya

Well said John.....thats what I was trying to say b4