Safe Speed Forums

The E-stop is a bit of a farce these days with ABS. As mentioned above it is simply plant the brake (even if you stall you won't fail) and hold on. You get ample warning since the examnier has to look over his shoulder before carrying out the test so are already braced for it.

In defence of a "reverse round the corner" test manouvre I think it is a very useful one. Any idiot can trickle a car round a corner in reveverse but what it does teach is observation. Three possible roads for a car to interrupt the manouvre + pedestrians. Also good for demonstrating how conditions change - there is less need to look through the drivers side window for traffic at the start of the manouvre but after 50% complete it is essential. It should also instill in people the importance of always reversing into the minor road and not into a busy dual carriageway!

On the topic of ABS - The situation where it come into it's own is when there isn't equal grip on all wheels. The ABS system can compute how much grip is available at each wheel and provide maximum braking force at each wheel while still giving the driver full control to steer.
I realise I'm probobally going to get jumped all over by defending ABS but I'd like to see anyone emergency brake AND swerve around an obsticle more successfuly in a non ABS car compared to one with ABS.

Assuming ABS does work like that (I don't know): that's a bit of a double edged sword. There may be instances where the wheels on one side of the car are on tarmac and the other side on slippery stuff. Such an imbalance could create a differential/rotational force, resulting with an uncontrolled swerve - into the incoming carriageway.

A compromise would be to apply maximum but equal braking pressure to each pair of wheels, the front and rear pair handled independently of each other.


Competent “old school” drivers should be able to manage it, using "cadence braking". I don't know if this technique is still taught. If not, and drivers nowadays are expected to drive vehicles with ABS, then it does make sense that e-stops need not be checked during the driving test.
I suspect new drivers would tend to drive cars without ABS (cheap old bangers).

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

I concur with Steve here. The purpose of ABS is to provide the maximum amount of usable braking, ie without creating an unbalanced situation.
This is the most useful feature of ABS, in that it prevents unbalanced braking, and so serving to prevent uncontrolled swerves or skids. This is especially useful when braking hard from high speeds, where unbalanced braking is more likely, even on good surfaces. (the longer the wheels are locked up for, the more likely it is for the car to get 'out of shape') Of course, the downside is that you have little or no braking on slippery surfaces. But, then again, you would't want to be doing high speeds on slippery surfaces now, would you?
Perhaps a useful compromise would be to have an ABS system which only operates above a certain speed.

Also, it's very unlikely that, in an emergency situation, you're going to want to be able to brake and steer at the same time. Any particular emergency situation is most likely going to call for either the one or the other, and not both. Most of the time, if you find yourself in the situation of having to do both, it means you've either made the wrong initial choice of which one to use, or you haven't been paying proper attention in the last few seconds - either way you've left it too late and you're screwed anyway.

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Only when ideology, prejudice and dogma are set aside does the truth emerge - Kepler

I must admit, I like the idea of a "switchable" ABS and one that switched off below certain speeds would certainly be beneficial on snow, (obviously, it would have to be triggered to stay on if you start continuous braking above a certain limit and not go off when that lower limit is reached.)

That way, good drivers would reduce their speed on snow (using gears, engine braking, gentle brake pressure), to the point that they would only need to start braking properly at very low speeds (below 15- 20MPH perhaps)....(i'm thinking about approaching junctions, here not emergency braking)

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

But this assumes that all the wheels lock or don't lock tgether. The nice thing about ABS is that it comes in when ONE (or more) wheels lock AND ONLY on that (those) wheel(s). (Try doing that with cadence braking!)

It DOES work like that - but only up to a point. It needs to balance the need for maximum braking on each wheel against the possibility that the car might spin if it actually did that. Early systems tended to "select high" or "select low" - meaning that when one wheel on an axle locked up, it had to choose between keeping the line pressure at the level of the UNlocked wheel, or reducing the pressure to both wheels until the locked whel started to turn. Such systems got ABS a poor reputation and, inded, weren't as good (in many cases) as a decent driver cadence braking. Since then, however, they have come a long way. The problem is that they are now often inextricably intertwined with Electronic Stability Control and Electronic Brake Force Distribution systems (so "switching them off" isn't really possible (well, not without maing the car potentially very dangerous)! One of the standard tests that an ABS car has to pass is, indeed, an emergency stop with two wheels on a low friction surface and two on a high friction surface. They also do tests where you stand on the brakes and in the course of the stop move from a high friction to a low friction surface and the other way round (high to low). In all these, the car needs to come out facing the same way as it went in.

As for old bangers not having ABS, those days are (close to!) being over now! There are very few cars without ABS (though there are still some with the old three-channel systems around).

I'd have thought the exact opposite, to be honest - that MOST emergency stops call for both steering and braking?!

Are you saying that there are no longer any cars being produced without ABS or are you saying that there are few cars of 15 years old or younger without ABS?

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

Couple of general observations:

1. Yes, it's well-documented that ABS doesn't work as well on soft snow or gravel - and for the reasons already stated. It always gets thrown up by those opposed to it, but I think it's importantto bear in mind just how few those situations are compared to all the others.

2. I think most current ABS systems automatically switch themselves off below a certain speed to allow the "ramp" effect of snow / gravel to help at speeds where it's likely to make a difference. However, that's pretty low - single figures of Km/h for the few vehicles I've seen data for. Also, as increasing numbers of cars take their road speed from the ABS sensors, and in the situation where the ABS is running, that data is likely to be pretty iffy, I don't know how they judge the speed at which to switch off!

3. I had the perfect opportunity to try some tests this morning. I live a hundred yards or so from an un-gritted 1-in-5 slope. Today, the surface was just melting, and it was slippier than a well-buttered, Teflon-coated eel! In every 20 yards or so, there were maybe half a dozen small patches of clearer tarmac - pretty much randomly positioned. From about 20MPH (going down the hill) I tried my preferred technique of planting the middle pedal and leaving it there. The ABS cut in and the car stopped (eventually)! It probaby took about half a dozen car-lengths to do so. All the time, the ABS was "doing its thing". The car doesn't have ESC. I then came back up the hill (with difficulty!) and tried again, cadence braking. To be fair, I didn't notice as much difference in stopping distance as I'd hoped. Whether or not my passage over it had affected the surface, I can't say. Come to that, although I started braking by the same tree each time, I can't guarantee that I took precisely the same path each time. Anyway, the ABS stop was better, but by less than a car-length. I did initially feel (when cadence braking) that I was going to do much better, but I think that was just a psychological ilusion as a result of me having "something to do" instead of just sitting there with my foot on the brake. The thing is, on both occasions I (and no other road user) was in any danger. If there was suddenly a kid in the road ahead, I'd be wanting the ABS every time!

4. I also tried that "Tyre Grip" spray. That proved pretty useless, unfortunately. I gave the front tyres a good squirt and let them dry for about 2 minutes. I then tried starting off on the slope - with absolutely no succcess. My hands were pretty sticky for a while though! It might have been VERY slightly better than without the spray, but the difference was too subtle for me to measure. With or without it, I couldn't do a hill start - I had to get a run at it. What's more, by the time I'd had a couple of goes and driven the few hundred yards home, the tread of the tyres wasn't sticky to the touch, so it had obvoiusly worn off. The bits of overspray on the sidewalls were still sticky though.

Both, I think!

In Europe, at least, there was a gentleman's agreement between the car manufacturers and the Commission to fit ABS as standard on all mass-produced passenger cars several years ago. (2006 rings a bell, but I'm not sure). The AA thinks it was 2004:

http://www.theaa.com/motoring_advice/ca ... afety.html

The actual "agreement" was very vague. The car manufacturers didn't want the Commission to mandate the "pedestrian protection" Directive and offered to fit ABS to all cars by 2003 and Daytime Running Lamps by 2002. Clearly, the latter hasn't happened and the Commission has imposed the "Pedestrian Protection" Directive anyway!

More here if you sufer from insomnia!
http://eur-lex.europa.eu/LexUriServ/Lex ... 89:en:HTML

I also don't see many 15 year old cars without it these days. My own cars is 22 this year and it has ABS! Obviously, I'm only talking mainstream European here. That excludes grey imports, various niche cars (like TVRs and some Lotus') and kit cars.

Thanks for that Mole, I didn't know that - and now do

One thing I've just realised about what I said before about the tendency for all-or-nothing ABS systems to spin the car: the outcome will be the same when fully locking all the wheels of a non-ABS car in the same described scenario, so even the old ABS cars should not be any worse than non-ABS ones.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

I think that the scenario that you are imagining (Am I correct in thinking you mean , that if a car is going down a narrow lane and had to pull over to the left , with the nearside wheels on grass or mud and the offside on tarmac, then had to brake sharply, the car would spin?) would never happen, I certainly have never experienced anything like it and I do a lot of driving on narrow lanes whereby you have to pull over and brake if an idiot comes round a blind bend a bit too quickly. For a start the offside wheels would have enough lateral traction to prevent this and i would imagine that the speed you would be needing to achieve a spin in these circumstances would be well in excess of NSL.

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My views do not represent Safespeed but those of a driver who has driven for 39 yrs, in all conditions, at all times of the day & night on every type of road and covered well over a million miles, so knows a bit about what makes for safety on the road,what is really dangerous and needs to be observed when driving and quite frankly, the speedo is way down on my list of things to observe to negotiate Britain's roads safely, but I don't expect some fool who sits behind a desk all day to appreciate that.

You're very welcome - Am I sad or what???!!!



Yes and no! All cars (ABS or otherwise, are supposed to have their rear brakes designed so that they never lock before the fronts. It's pretty hard to lock most rear brakes, except on really slippy surfaces. There's something called the "adhesion utilisation curve" in the regs (that I don't fully understand!) which the car needs to satisfy. On pre-ABS cars, this used to be set pretty low and the rear brakes didn't do anything like as much work as they were capable of doing in most circumstances. I think the main part of the reason why my informal experiments didn't show much difference between cadence and ABS was that the ABS software wasn't allowing any wheels with more grip to use it, for fear of spinning the car, so, in effect, it's still not letting individual brakes do as much work as they could have done.

That precise situation happens to me sometimes. I can't say "often" but it has definitely happened. Round here, it's usually as I'm going down hill on a single track road. I'm in the "give way" position and there are times when something comes the other way from round a bend and I have to take to the grass with two wheels before I can get to the next passing place. On such occasions, the ABS may well cut in and I leave it to do its thing. As you say, the two wheels on tarmac have good lateral grip, so it can allow the (say) left hand front wheel to lock and unlock on the grass whilst still managing a lot of braking on the two offside wheels. I wouldn' be able to do that if I was cadence braking.

It may well be fair to say that many drivers might never be in that situation (where the wheels of one side of the car was on slipperier stuff), more so for city drivers. Then again, I bet most drivers will never be in a position where the airbag must deploy - but I'm sure most would still prefer to pay for that protection anyway.

My old commute (London/Portsmouth) took me cross-country. Many times I have seen the outer section of the tarmac was wet and muddy, while the rest remained completely dry. I'm guessing these streams were run-offs from fields. This was normal after rain.

There is also the issue of puddles at speed, especially within ruts, where the tendency to aqua-plane will reduce available grip. Of course one shouldn't be going that quick and really shouldn't be in such a position such that one has to brake hard in that environment, but it does happen.

I do take the point about lateral grip, but I given the advent of 'good' ABS, I would prefer to not bet on that unknown grip.

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Views expressed are personal opinions and are not necessarily shared by the Safe Speed campaign

It will constantly asses the "unknown grip" as the braking is taking place. Better still, a car with ESC will do even more (not quite sure how) to constantly check and adjust the car's attitude. I'd have thought that quite a few people in the recent weather would have had two wheels on slippy stuff and two on "better" (if not exaclty "grippy") stuff?