Disturbing Acc Behaviour

[jasonc]

I know there has been lots of discussion on here about ACC and I am well aware that there are some situations that you cannot expect it to deal with correctly but thought I'd share an experience I had this morning since it was a situation that I felt should not have caused a problem and it took me by surprise.

For the record I am a big fan of ACC and would recommend it to anyone but I do still limit it's use to motorways and dual carriageways (and big stop/start traffic jams on other roads) because I think that there are just too many variables in other situations for the current system to deal with.

Anyway this morning I was in normal slowish traffic on the M4, travelling in lane 2 with the ACC set to 70ish (distance 3) but travelling at about 40mph because that was the speed of the cars in front. I was approaching my exit so went to slot in behind a car in lane 1 - I've done this a hundred times with the ACC on and normally the ACC gently backs off the throttle and you settle in lane 1 at a sensible distance to the car you pulled in behind. Today for some reason as I changed lanes instead of backing off the throttle the ACC floored it and I accelerated straight at the car in front that was already in lane 1. I reacted by braking which obviously disengaged the ACC so we'll never know whether it would have driven straight into the car or not - I heard the Pre Sense alarm noise so I suspect that the car would have stamped on the brakes if I hadn't (don't know which warning was shown on the DIS because by the time I looked down it had gone).

Here's the video (looks a lot less dramatic that it felt at the time!):



Any ideas? My only thought was after looking back at the video the car in lane 1 was quite a long way over to the left of the lane so perhaps the ACC couldn't see it until it was too late?

 

[veeeight]

Given that you didn't appear to have a lot of distance from the back of the car in Lane 1, I would say that the radar sensor had a narrowish beam, and "saw" the gap between Lane 2 and Lane 1, and accelerated to what it saw as an empty lane.

 

[dts439]

I'm no expert on this but as you go left there is a brief period when directly in front of the car it there is nothing until the 2nd car in lane 1. I don't know how narrow the radar beam is on ACC or what frequency it looks/checks. Also given at that moment you are doing 40 and the cruise speed is 70 it may treat the sudden gap as a chance to accelerate hard and by the time it looks again its a bit late.

Assume the manual says you are supposed to switch ACC off before changing lanes?

All interesting stuff for me as I've specced ACC on new car.

 

[cemerson]

No, manual doesn't say you are supposed to switch it off before switching lanes, it's designed to cope with it.

Interesting situation... but I have noticed that it takes about a second (maybe a bit less) to assess what is going on in a new lane when you change, and you did (in my opinion) change lane very close behind the car already there. I think it probably would have coped with a bigger gap

 

[jasonc]

No, manual doesn't say you are supposed to switch it off before switching lanes, it's designed to cope with it.

Interesting situation... but I have noticed that it takes about a second (maybe a bit less) to assess what is going on in a new lane when you change, and you did (in my opinion) change lane very close behind the car already there. I think it probably would have coped with a bigger gap

I think you are probably right, I'm sure I've had a few occasions where the car accelerates into a new lane only to find a car there and have to back off - it's not an issue when the car it finds is a fair way in front so you wouldn't normally think anything of it.

I don't know whether the ACC relies solely on the radar or if it is tied in to other systems. For example, it would seem sensible to me that if the indicator is on then some kind of change (e.g. a lane change) is clearly in progress and the system should refrain from nailing the throttle for a second or two until it gets a clear view of the new road situation.

 

[0B1001001]

I don't know whether the ACC relies solely on the radar or if it is tied in to other systems. For example, it would seem sensible to me that if the indicator is on then some kind of change (e.g. a lane change) is clearly in progress and the system should refrain from nailing the throttle for a second or two until it gets a clear view of the new road situation.

It is definitely linked to indicators - if you come up behind someone on a motorway and indicate to overtake, it will allow you to close up more a part of the natural lane change/overtake process; if you don't indicate but do the same manoeuvre, it will brake as it thinks you haven't seen the car and doesn't know you plan to overtake it.

I am not sure if you indicated but that could be related, as could the proximity of the car you pulled in behind plus its positioning in the lane - suspect it's one or more of those factors.

 

[jasonc]

It is definitely linked to indicators - if you come up behind someone on a motorway and indicate to overtake, it will allow you to close up more a part of the natural lane change/overtake process; if you don't indicate but do the same manoeuvre, it will brake as it thinks you haven't seen the car and doesn't know you plan to overtake it.

I am not sure if you indicated but that could be related, as could the proximity of the car you pulled in behind plus its positioning in the lane - suspect it's one or more of those factors.

That's interesting. I definitely indicated (I never change lane without indicating!). If the ACC knows that the indicator is on then perhaps it assumes that the lane you are moving into is clear until it sees otherwise. The way that it accelerates when you are changing lane and then backs off when it notices a car within range would support this but since the radar clearly has a very large blind spot this is quite dodgy! It knows which side of the road we drive on so perhaps it should be more cautious when moving into a lane to the left since there is more likely to be a slower vehicle there. I think the guys who designed this system must have had a lot of sleepless nights trying to find a balance between safety and making it useful - overall it is impressive but there is definitely a lot of room for improvement in the future.

 

[veeeight]

Yep - buy and A6 and it has dual radar sensors, and its coupled to the camera behind the rear view mirror. This can also recognise cars ahead of you indicating to come into your lane, and your can will drop back accordingly.

In the humble A3 - it's only a basic system, with all the associated limitations.

 

[Vertigo1]

Sorry but I have to say it - this is why systems like this can't be trusted and are potentially dangerous. They can't cope with every situation and will make mistakes. No matter how many disclaimers the manufacturers cover themselves with and how often they tell you it's just an "aid" and you should remain in control at all times, people will start to trust systems like this too much and get lazy and that's when accidents will happen. I've already told the story on here about a friend in Germany whose 5 series lost sight of the car in front round a bend at the end of a slip-road and promptly stepped on the throttle to speed back up to the speed he'd set on the motorway much earlier.

Luckily you (and my friend) had your wits about you but the next person may not do and what happens then? I know I'll get flamed by all the ACC fans in here but I don't care. Too many accidents are already caused by people not paying attention to what they're doing behind the wheel and systems like this just promote more disassociation from the task of driving.

 

[cemerson]

The front camera is used for the A3's ACC as well, if present.

 

[cemerson]

Sorry but I have to say it - this is why systems like this can't be trusted and are potentially dangerous. They can't cope with every situation and will make mistakes. No matter how many disclaimers the manufacturers cover themselves with and how often they tell you it's just an "aid" and you should remain in control at all times, people will start to trust systems like this too much and get lazy and that's when accidents will happen. I've already told the story on here about a friend in Germany whose 5 series lost sight of the car in front round a bend at the end of a slip-road and promptly stepped on the throttle to speed back up to the speed he'd set on the motorway much earlier.

Luckily you (and my friend) had your wits about you but the next person may not do and what happens then? I know I'll get flamed by all the ACC fans in here but I don't care. Too many accidents are already caused by people not paying attention to what they're doing behind the wheel and systems like this just promote more disassociation from the task of driving.

You have no evidence to back up your claims (and pretty sure there will be none too). You are just using anecdotes. In fact, 2 anecdotes in which NOTHING HAPPENED!

 

[lucas-suisse]

Sorry but I have to say it - this is why systems like this can't be trusted and are potentially dangerous. They can't cope with every situation and will make mistakes. No matter how many disclaimers the manufacturers cover themselves with and how often they tell you it's just an "aid" and you should remain in control at all times, people will start to trust systems like this too much and get lazy and that's when accidents will happen. I've already told the story on here about a friend in Germany whose 5 series lost sight of the car in front round a bend at the end of a slip-road and promptly stepped on the throttle to speed back up to the speed he'd set on the motorway much earlier.

Luckily you (and my friend) had your wits about you but the next person may not do and what happens then? I know I'll get flamed by all the ACC fans in here but I don't care. Too many accidents are already caused by people not paying attention to what they're doing behind the wheel and systems like this just promote more disassociation from the task of driving.

I originaly planned to take the ACC option on my S3 but the Audi dealer frankly didn't recommend it for safety reasons... Finally I did not go for it. Just my two cents...

 

[veeeight]

The front camera is used for the A3's ACC as well, if present.

I think that used to be the case, when combined with the other DA options (and you got the higher ACC speed limit) - but I think they have stopped this feature.

 

[cemerson]

Oh, was listed on the configurator/brochure when I ordered! Mine seems to do an incredibly good job of tracking cars around corners and around lanes, I've always assumed this is the camera input at work.

 

[veeeight]

Just one version of ACC for the A3/S3 on the brochure/configurator now. At the lower ACC speed limit !

 

[cemerson]

I have an odd combination, of the camera-enhanced ACC, but with the 100mph limit (not that I need more than that!)

 

[veeeight]

And also a non-user updatable version of the MMI Maps !

 

[cemerson]

Nope, I can update my maps. Have done it once already. I can also use rSAP or separate SIM for Audi Connect while still connected to my phone over bluetooth. Starting to think I ordered right in the sweet spot for this car!

 

[jasonc]

Sorry but I have to say it - this is why systems like this can't be trusted and are potentially dangerous. They can't cope with every situation and will make mistakes. No matter how many disclaimers the manufacturers cover themselves with and how often they tell you it's just an "aid" and you should remain in control at all times, people will start to trust systems like this too much and get lazy and that's when accidents will happen. I've already told the story on here about a friend in Germany whose 5 series lost sight of the car in front round a bend at the end of a slip-road and promptly stepped on the throttle to speed back up to the speed he'd set on the motorway much earlier.

Luckily you (and my friend) had your wits about you but the next person may not do and what happens then? I know I'll get flamed by all the ACC fans in here but I don't care. Too many accidents are already caused by people not paying attention to what they're doing behind the wheel and systems like this just promote more disassociation from the task of driving.

You have a valid point of view but personally I don't agree with it.

I do agree that as automated systems like ACC become far more widespread on cars we will start to see reports of accidents where the automated systems are listed as a factor in the accident but I believe that at the same time there will be a significant number of accidents that will be prevented by the automated systems.

There is already a clear split of opinion on automated systems in cars and I suspect this debate will drag on for years but I think that anybody who is totally against them should be grateful that they currently have a choice and these systems can be turned off because in 10 or 20 years I doubt that you will be able to disable the cars automated systems anymore than you can currently disable the airbags or ABS.

One thing I am sure of as I travel up and down the motorway everyday is that I would actually much rather look in my rear view mirror and know that the car behind is being controlled by a computer than by some of the idiots that are behind the wheel - the computer will never tailgate me and will never run in the back of me.

In fact you said it yourself -

Too many accidents are already caused by people not paying attention to what they're doing behind the wheel

so give them all a system which IS paying attention and will hit the brakes when they don't!

 

[Vertigo1]

You have no evidence to back up your claims (and pretty sure there will be none too). You are just using anecdotes. In fact, 2 anecdotes in which NOTHING HAPPENED!

What claims? I've made no claims at all, merely stated my opinion, to which I'm entitled despite your belligerence.

Anecdotal evidence is still evidence. I'm not claiming it's a common occurrence, merely pointing out that these systems can and do get things badly wrong.

 

[0B1001001]

It's an aid, not an autopilot. Learn what its weaknesses are and drive anticipating them.

Personally, I use it frequently at all road speeds but only for "simple" driving. Junctions or other complications (undertaking due to traffic speed, etc.) I make better decisions and take over. Having never had a system like this before, I would not hesitate in getting it again.

 

[cemerson]

What claims? I've made no claims at all, merely stated my opinion, to which I'm entitled despite your belligerence.

And I'm stating your opinions (or claims, because they were both) are not backed up by data.

Anecdotal evidence is still evidence.

It really isn't. The plural of 'anecdote' is not 'data', as the saying goes!

 

[Martinbanshee]

I've ordered ACC and I'll use it when the time is right but it is an aid and I'll always be ready to take full control. Every system has limitations, it's a case of knowing them and adapting to them.

It not for everyone though, the wife is scared to use standard cruise control never mind ACC.

IIRC, Golfs have ACC as standard now, it would be interesting to see the accident stats compared to older Non-ACC Golfs.

 

[leosayer1]

It's an aid, not an autopilot. Learn what its weaknesses are and drive anticipating them.

Personally, I use it frequently at all road speeds but only for "simple" driving. Junctions or other complications (undertaking due to traffic speed, etc.) I make better decisions and take over. Having never had a system like this before, I would not hesitate in getting it again.

Same here.

ACC is at it's best when you're in a stream of traffic or in a traffic jam, not when overtaking and not changing lanes.

 

[a3_phil]

Just like the Joker said, if it's part of the plan no-one gets upset.

If 2,000 people die on the roads next year due to driver error, no-one will bat an eyelid.

If that drops to 1,000 but some of them are killed due to computer error, people will go mental.

Perception is unfortunately as persuasive as cold hard numbers, but in time I think people will come to accept the overall reduced risk that many of these systems bring.

 

[NickyF]

I've never driven an ACC equipped car so my view point is illinformed but I tend to agree with Vertigo. I feel safest on the motorway when I'm driving, arguably too fast (not too bad honest), in the outside lane overtaking. Reason being that I'm focused on the task in hand, expecting people to pull out, ready for the unexpected. If I dawdle along I lose focus, get bored and distracted and end up not paying much attention to what's going on around me - I don't want to be like this but I can't help it. Something like ACC may make me nod off, I was never going to tick that box despite it being pretty cheap for some cool tech.

 

[monkeyhanger]

ACC can be a dent saver, maybe even a life-saver but it does have it's limitations. Some people will always use systems like these as an excuse to stay switched off - check their texts on the move, apply make-up, etc. There will always be people like that on the road (hopefully they will stick to their Fiat 500s so we can spot them easily). For someone on the ball all the time when they're driving, 99 times out of a hundred it'll be a false alarm when the ACC bangs the brakes, but that 100th time might be the time you're glad you left it switched on. I have got into the habit of just touching the brakes when a car is slowing in front of me to turn and I know it will be gone out of my path before I would be in danger of hitting it if carrying on at around the same speed or just easing off the throttle a little - just to save the false alarm. going around a bend and something in another lane ahead of me causing an alert is my biggest peeve with the system.

It's scary how detached you can be from driving and still get from A to B with all these driving aids, saving the skin of some people not too perceptive on the road. With ACC, lane assist and an auto box (so the system can brake through the gears without potentially stalling, as is the danger with a manual if more than a warning bang on the brakes is given), if they could intelligently link to the Satnav with an inputted destination, there doesn't seem too much else to add for the car to be able to drive itself from A to B.

 

[NickyF]

hopefully they will stick to their Fiat 500s

That'll be me then, I drive a 500c twinair to work everyday, it's a great car. My makeup is always perfect.

 

[monkeyhanger]

Sorry to tar you all with the same brush , but on my commute, i'm pretty timely and see the same cars on the same stretch of the coast road a lot of the time. Amongst the attention deficit drivers I see regularly are a lass in a powder blue Fiat 500 applying her make-up or brushing her hair, another 500 (with the yellow/chequered New York Taxi looking stickers) with a lass eating toast at the wheel and drinking coffee while steering with her knees, and a fair few texters in other (non-500) cars. There's a thread to start - what's the craziest thing you've seen someone do while in charge of a moving car?

 

[veeeight]

ACC is lovely, let's me fiddle with the MMI checking texts whilst in a traffic jam

And I can lower my sunvisor down and look at the vanity mirror to apply lippy too, don't need to look out of the front of the car as ACC takes care of this. I've also normally got the face vents at full blast, blow drying my hair during my commute.

And the flat bottomed steering wheel makes steering with your knees a doddle. Perfect for when my hands are full.

 

[Relliott6879]

My car is specced with cruise control as part of the comfort pack. Is this ACC or just 'vanilla' cruise, ie it'll keep cruising straight into a brick wall if the driver doesn't dip the brake or clutch to deactivate it? I've actually no issue with either system, I retro-fitted the latter to my Cougar and love it for motorway miles, I was amazed when first using it how less tired I felt at the end of a long journey without having to constantly assess and make minor adjustments to road speed, something we must subliminally do hundreds if not thousands of times during a long journey.

Back to my original question though, is the cruise in the comfort pack a lower-tech version, or is all A3 cruise ACC?

 

[veeeight]

It will be vanilla cruise, unless you pay an extra £350 to upgrade it in the Comfort Pack to ACC.

Very useful for when you want to put your make up on, paint your nails, check Facebook etc.

 

[Relliott6879]

Cheers.

 

[monkeyhanger]

It will be vanilla cruise, unless you pay an extra £350 to upgrade it in the Comfort Pack to ACC.

Very useful for when you want to put your make up on, paint your nails, check Facebook etc.

Did you send that reply while at the wheel?