Adaptive cruise control, dangerous

[sussamb]

@DaveT70

Never said it would 'slam on the brakes', I was replying to DG97 who said slamming on your brakes wouldn't necessarily make you unskilled, when 'slamming on your brakes' and doing a 'hard stop' are two completely different things. The former is a driver panicking, the latter a skilled driver and done properly is progressive and smooth.  Incidentally if ACC 'slams on the brakes' I definitely don't want it anywhere near me

As for someone slamming into the back of you being their problem you're so very wrong, often it's the folks in the car in front who come off worse.  Trust me, I've been there and seen it many more times than I care to remember.

[DG97]

20 minutes ago, sussamb said:

@DaveT70

Never said it would 'slam on the brakes', I was replying to DG97 who said slamming on your brakes wouldn't necessarily make you unskilled, when 'slamming on your brakes' and doing a 'hard stop' are two completely different things. The former is a driver panicking, the latter a skilled driver and done properly is progressive and smooth.  Incidentally if ACC 'slams on the brakes' I definitely don't want it anywhere near me

As for someone slamming into the back of you being their problem you're so very wrong, often it's the folks in the car in front who come off worse.  Trust me, I've been there and seen it many more times than I care to remember.

The difference between slamming your brakes on and doing a hard stop to me are just a difference in choice of wording but we can disagree on that one 😉 one is a bit more “slang”, the other a little “more formal”

to be fair, there’s no doubts that quite often the person in front can come off worse than the person who rear ends you. I think what people including me are trying to say is that no matter whether you use acc or not, you can’t control how close someone is behind you. 

[Guy Heaton]

My old c class would put the brakes on to maintain speed on downhill on cruise.

That's all I want really.

[Blatto]

11 hours ago, DG97 said:

If the car reacts immediately and someone rear ends you, that’s no different to you reacting and someone going into the back of you. It’s their fault for being too close to you. 
 

in terms of anticipation, you’re still in control of the vehicle - you’re simp

11 hours ago, DG97 said:

in terms of anticipation, you’re still in control of the vehicle - you’re simply using a driving aid. If things get dangerous or you see a hazard, turn it off. As simple as that. 

 

I think you are misunderstanding what I meant in terms of controlling the person behind you who is following too close. Or maybe I didn't explain it very well.

Yes I agree it's their fault for being to close and  you don't have many choices in stopping the idiot behind doing it. 

You can get annoyed and try slowing down and hoping they will back off or pass you, but that's not a sensible option and in many circumstances just as dangerous. You also might antagonise them into road rage and make the situation much worse.

You can brake test them, a stupid and dangerous option.

You can try and find a safe spot to pull over and let them pass but that's certainly not possible on the motorways.

The only sensible option if someone is following too close is to leave an even bigger gap to the vehicles in front of you so that you can see much farther ahead to spot any dangers and if you do see the situation is going to require hard braking you will have the space/time to slow down very gently thereby controlling/reducing  the speed of the person behind. You can bring them to a gentle stop without any harsh braking in most cases.

4 hours ago, DaveT70 said:

If someone is behind you, too close, with no ACC and slams up your back end, that's their problem

It's their fault for following too close but it's not just their problem, it's your health and vehicle that are going to get damaged as well, and in some circumstances you could lose your life. So it's your problem too.

 By leaving much bigger gaps you can stop or at least reduce the impact of the idiot behind you. 

My argument against Adaptive cruise control in these incidents (or at least the ford implementation in the Fiesta) is that it doesn't leave enough of a gap to do that, ,in settings 1, 2 or 3 it is way too close for you to have and good view of the road ahead and if for any reason it fails you have no chance of stopping in the distances it leaves.

11 hours ago, DG97 said:

in terms of anticipation, you’re still in control of the vehicle - you’re simply using a driving aid. If things get dangerous or you see a hazard, turn it off. As simple as that. 

Yes you are still in control of the vehicle but your opportunity for anticipation at the distances settings 1, 2 or 3 of the Ford system leave you at is severely impaired, you simply cannot see far enough ahead at those following gaps. You should be looking way into the distance not just 4 or 5 cars in front. You can turn the system off but that would be pointless at those distances you will just crash into the vehicles in front in most cases.

I've seen a VW system that looked pretty good and could be useful in a lot of situations but having test driven the Ford system and read their descriptions of the stupidly small gaps it leaves I wouldn't use it.

I've nothing against it in principle just the current Ford one is unsafe. 

 

 

[sussamb]

3 hours ago, DG97 said:

The difference between slamming your brakes on and doing a hard stop to me are just a difference in choice of wording but we can disagree on that one 😉 one is a bit more “slang”, the other a little “more formal”

Nope, just shows you don't understand how to do it or more likely have never been taught properly. Slamming brakes on is how a poor or inexperienced driver reacts. A hard stop, which is a progressive braking movement and certainly isn't the same, feels smooth and under control. Do an advanced or blue light course and you'd understand.

[DG97]

4 minutes ago, sussamb said:

Nope, just shows you don't understand how to do it or more likely have never been taught properly. Slamming brakes on is how a poor or inexperienced driver reacts. A hard stop, which is a progressive braking movement and certainly isn't the same, feels smooth and under control. Do an advanced or blue light course and you'd understand.

Keeping in mind that the discussion was on opinions of safety of ACC, and that really goes off topic (in quite an unnecessary manner!), i think its a good idea to agree to disagree on the matter and begin to leave it at that!

To address your concern of my understanding of "slamming brakes" or "progressively braking" - relatively clear difference between this but down to the choice of wording. Previously, a few mentioned brakes being "slammed on" or doing a "hard stop", seems a bit daft to say it, but people interpret that in their own ways regardless of driving ability. If anything, my slightly sarky advice to return your way is to express what you mean a little bit more clearly 😉

I do agree with @Blatto though in that the only way to reduce the impact of a tailgater is to keep a large enough distance in front, and I do think the ACC leaves a gap that is adequate for this on the right settings.

I don't agree that ACC would be a major contributor to someone rear ending anyone though as the ACC braking I feel has always been relatively progressive and predictable rather than a binary on/off. 

 I can only go by my own experience of ACC - the gap on setting 3 and 4 is bigger than I'd say 75% of cars seem to keep anyway and I've never had it get me into a dangerous situation with cars in front or behind me. Regarding anticipation - i'll go back to what I said earlier with ACC being a driving aid, at gap 3 or 4, i see far enough to see upcoming hazards and if I feel a dangerous situation is coming up, I'll simply switch it off and take over. Though I appreciate the comment of it might be too late at the time, from my experience of using ACC in the way that I do, it's not the case though again, I appreciate others may feel differently. 

[Blatto]

34 minutes ago, DG97 said:

 I can only go by my own experience of ACC - the gap on setting 3 and 4 is bigger than I'd say 75% of cars seem to keep anyway

I'd certainly agree with that, unfortunately 100% of those 75% are following way too close if they are following at smaller distances than setting 3 or 4. Setting 4 is the absolute minimum you should be to give yourself a chance of avoiding an incident. Like I've said before what's the benefit of following so closely. Increase you chances by moving back more, there's nothing to lose and everything to gain.

 

39 minutes ago, DG97 said:

Keeping in mind that the discussion was on opinions of safety of ACC, and that really goes off topic (in quite an unnecessary manner!)

I'm not sure it's gone that far off topic my original reason for starting this thread was because I see so many accidents caused by following too close, I just find it incredible that so many people fail to see the danger of following that close  and the benefits of leaving sufficient gaps. Inevitably this will bring the conversation around to braking/ following distances, anticipation etc...

When I first looked at the ACC option I was optimistic that as more and more cars start to include this as standard that it would reduce the number of people following too closely.

Sadly based on the ford settings it appears to make them follow at unsafe distances and will likely lead to more people thinking that's an acceptable distance. I can assure you it isn't.

You only need to look at the average reaction time/thinking distance of the majority of people and the stopping distance of even a high performance car on top notch tyres to realise that 28 metres at 62 mph as quoted for setting 1 in the Ford manual is suicidal/homicidal. An average road car takes about 30 metres to stop from 62mph. 62mph is 27.7 metres per second.

1 hour ago, DG97 said:

I do agree with @Blatto though in that the only way to reduce the impact of a tailgater is to keep a large enough distance in front, and I do think the ACC leaves a gap that is adequate for this on the right settings.

To be able to safely deal with tailgaters in the way I was describing needs at least a 200 metre gap.  even on setting 4 of the Ford sytem you are not even 1/3rd of that distance back.

1 hour ago, DG97 said:

I don't agree that ACC would be a major contributor to someone rear ending anyone though

I wasn't suggesting that it was a cause of  someone rear ending you, only that it doesn't  leave a big enough gap to slow the tailgater  in the way I was describing.

In that respect it's no better or worse than someone driving at those distances without the ACC.

 

[sussamb]

@Blatto Good to see someone drives with care and consideration, and understands the relevant physics 

[Blatto]

I did start taking advanced Driving lessons back in the mid 1990's had about 8 lessons but then lost my job so couldn't afford to carry on. I always meant to try again at some time but never got round to it. Plenty of good lessons available to view on You Tube now which explain a lot of the techniques.

Sadly I think these days many people treat driving their cars like an extension of their nice comfy living room. Heaters on, music so loud you can't hear the engine or emergency sirens.Eating food (saw that tonight on the way home, some girl tipping crisps into her mouth whilst driving up the sliproad, she then stalled at the roundabout)

Oblivious to the things going on around them.

A false sense of security with the comfort and ease at which a modern car will sit at high speeds.

And of course the most dangerous of all, using the mobile phone. It really is time they got to grips with that menace. Instant 12 months driving ban and phone crushed if caught.

Quite how people think they can control a car safely  whilst using a phone is beyond belief.

Following too close is just another one people have become blase about. I get the impression people see others all following 2 or 3 cars lengths apart on the motorway and think that's normal. Or they are more likely just not thinking at all.

 

 

 

 

 

 

[sussamb]

1 hour ago, Blatto said:

 Or they are more likely just not thinking at all.

 

 

 

 

 

 

Probably that.  I've even had folks pull out of side turnings as I was closing at speed with blue lights flashing and sirens on, or they see the car in front of them pull over (as they've seen me) and then they pull out to overtake it without a glance in the mirrors and then wonder why they get the benefit of my bullhorn

[Stoney871]

Do an advanced or blue light course and you'd understand.

Been there, done that, many times [emoji41]

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[Mavroz]

Didn't give it much thought until earlier this morning when I was sat in queueing traffic on the dual carriage way going to work.

The road bends slight and I counted 15 cars in front of me to the roundabout.

I think someone suggested leaving a minimum of 17 car lengths between their car and the car in front on a motorway at 70mph.

That is some crazy distance. For me 6 or 7 car lengths maybe but 17 is way too much?

 

[sussamb]

Then you're clearly a risk to yourself and others https://www.rac.co.uk/drive/advice/learning-to-drive/stopping-distances/

 

Note too that the '2 second rule' at 70 is equivalent to 62 metres, so that is way way more than 6 to 7 car lengths, and probably close to the 17 you seem so quick to dismiss (depending on what car size you choose).

[Bobr]

This is from the AA:

 

[Bobr]

2 hours ago, Mavroz said:

I think someone suggested leaving a minimum of 17 car lengths between their car and the car in front on a motorway at 70mph.

That is some crazy distance. For me 6 or 7 car lengths maybe but 17 is way too much?

 

Please let me know when you're on the motorway.   I'll stay at home.

[Stoney871]

Then you're clearly a risk to yourself and others https://www.rac.co.uk/drive/advice/learning-to-drive/stopping-distances/

 

Note too that the '2 second rule' at 70 is equivalent to 62 metres, so that is way way more than 6 to 7 car lengths, and probably close to the 17 you seem so quick to dismiss (depending on what car size you choose).

Blimey, you count to two slowly. [emoji38]

 

Seriously now, please, don't be so preachy.

Through my job I've attended many RTC myself and agree many people can't judge adequate spacings between cars but all you can realistically do is allow enough space for yourself in front and plan an escape space if you get chopped off by a lane changer.

You can't make any difference to tailgaters, just get out of their way when safe to do so and let them rush their way off the mortal coil if they so choose to do so.

Of course I usually have the option of a pop-up led board to tell them to slow down.

(Btw I'm an advanced response trained driver and also was a t-pac instructor for 3 1/2 years[emoji41]).

 

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[Blatto]

7 hours ago, Mavroz said:

I think someone suggested leaving a minimum of 17 car lengths between their car and the car in front on a motorway at 70mph.

That is some crazy distance. For me 6 or 7 car lengths maybe but 17 is way too much?

It was me who mentioned that figure. Based on the "only a Fool brakes the 2 second rule" with 2 seconds being the minimum distance you should be following

It's still a decent rule and it takes into account  the thinking distance and the stopping distance.

At 70mph you are doing approx 32 Metres per second so a 2 second gap is 64 metres, with an average car being just over 4 Metres in length 64/4 = 16 Cars lengths.

I added an extra 1 for luck. Because at that distance you will still be lucky not to collide with the car in front if he absolutely slams on the anchors. And that's if you are really on the ball with your braking, leave it an extra 1/2 a second and you will hit them hard.

At 6 or 7 cars lengths you suggested you will be about 7 x 4 = 28 metres back, that's less than the thinking distance. Yes I realise the guy in front has got a stopping distance too but he's got the jump on you because you will be unlikey to react until you see his brake lights. It's then fairly unlikey you will be at the  maximum braking ability of your car straight away , 1 second of delay and you'll have less than 30 metres left to stop which is pretty much the limit for most cars at that speed. You might be lucky and get away with it, by why risk your life by driving at the absolute limit. Just move back a bit, 100 metres at 70mph about 25 cars lengths will give you a much better chance.

 

 

 

[alexp999]

7 hours ago, Mavroz said:

Didn't give it much thought until earlier this morning when I was sat in queueing traffic on the dual carriage way going to work.

The road bends slight and I counted 15 cars in front of me to the roundabout.

I think someone suggested leaving a minimum of 17 car lengths between their car and the car in front on a motorway at 70mph.

That is some crazy distance. For me 6 or 7 car lengths maybe but 17 is way too much?

 

Don’t forget there are gaps between each car in a queue of traffic. 
 

When talking about distances measured in car lengths, it’s as if they were literally nose to tail, not the distance if there were that many cars queuing. 😉

[Blatto]

19 minutes ago, Stoney871 said:

Seriously now, please, don't be so preachy.

Not so sure it's a case of being too preachy. I realise it might come across as a bit of a lecture, but for myself I am just trying to demonstrate to people that what they consider to be a safe gap isn't. If it was to get just 1 person reading these forums to think about their following distances and act on it then it's been worthwhile for me. 

19 minutes ago, Stoney871 said:

and agree many people can't judge adequate spacings between cars

 Which is why the 2 second rule is again quite useful as you can count 2 seconds fairly reliably and as the car in front passes a stationary object start counting and if you pass before you get to 2 you are way too close. Personally that's still to close to the limit, 3 or 4 seconds is a lot safer.

It's also quite easy to get a sense of 100 metres if you are approaching a motorway off ramp as the 3, 2, 1 markers are 100 metres apart.

 

 

[Blatto]

9 minutes ago, alexp999 said:

When talking about distances measured in car lengths, it’s as if they were literally nose to tail, not the distance if there were that many cars queuing. 😉

I was going to mention that myself but you beat me to it 🙂

 

[sussamb]

2 hours ago, Stoney871 said:

Blimey, you count to two slowly.

Possibly

[Bobr]

2 hours ago, Stoney871 said:

Through my job I've attended many RTC myself and agree many people can't judge adequate spacings between cars but all you can realistically do is allow enough space for yourself in front and plan an escape space if you get chopped off by a lane changer.

Me too.   Something that nobody has considered in this discussion is that if you take your eyes off the car in front for a split second if you are too close then some poor copper will be having to tell your family that you didn't stop in time.

[Stoney871]

Had to deliver a Death Message (called a "deathogram" in olden days when a dark humour was permitted) three months into my probation period and I think I was just as upset about it as the deceased persons partner was.

Horrible to do as you just know you've torn their heart out and stamped on it.

They always say your first is the hardest but tbh I don't think they ever get easy (and I don't think they should ever get to be unless you are a cold blooded b*stard).

Thankfully most of our messages are passed by trained Liaison Officers now so the procedure is more thoughtful.

I had one colleague that went to a partners house holding an evidence bag containing a wallet, smashed watch and a shoe all drenched in blood, got the partner to sign for the items after verifying they were her Husbands effects, gave her the mortuary number and walked away with no feeling or compassion, not even a half-hearted attempt at softening the blow.

Suffice to say he didn't get asked to deliver a message again (he's a DI now and still a cold swine).

I've never got hardened against the scene of a fatal RTC and truly hope I never do because that to me would be the time to just walk away from the job.

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[Mavroz]

I understand what you are all saying about stopping distances. In my little experience of doing a lot of motorway driving other than mainly airport runs etc the distances that are stated seem virtually impossible.

I am doing 70mph in lane 1, a car indicates and pulls into lane 1 Infront of me. The distance to it,I estimate is around 7 or 10 lengths so now I have to decelerate to increase this distance to 17+ lengths again. While I am doing this, the car behind me is rapidly closing the gap between us. He pulls into lane 2 to overtake me.

Once he has overtaken , he indicates and pulls into lane 1 Infront of me. The gap is no longer 17+ lengths. So do I decelerate again, forcing the car behind to decelerate or do I accelerate and overtake to get back Infront of the slower moving vehicle?

Maintaining the gap may well be ideal on paper but in practice, if every road user did it it is regularly impossible to do this, especially on dual carriage ways at 70 mph. 

I am not just talking about 70mph roads either. 40,50 and 60 are all the same with stopping distances being overlooked. 

Oh for an idyllic world.. 

 

 

[sussamb]

It's simple enough … many of us manage it