ACC when approaching stationary traffic - oops !

mls · Sep 2, 2015

I use ACC a lot, and I like it. I live in London so I'm pretty much always in traffic, so the stop start feature is great - I have the S-tronic S3 Sportback.

I have found recently, that when I'm on an empty stretch of road and the acc is driving at its (say 40mph) setting for a while, it does not seem to see stationary car infront when I come to a traffic light for example. No green icon appears on the dash to say that it can sense a car infront, and it just keeps going.

I leave it to the last minute, then brake to avoid hitting the car.. but shouldn't the ACC sense the stationary car and slow down/stop accordingly ?

Has anyone else had this ?

Thanks

NATOuk · Sep 2, 2015

If you change your DIS screen to 'Assist' you should see your car at the bottom and some horizontal lines above it.

As you approach a car, you should see another car appear at the top

ie,

TARGET CAR
=
=
=
=
YOUR CAR

which shows that the system has detected a car in front. As you approach there are two arrows either side of the horizontal lines which should get closer to the middle green section then once they go towards the red section the car should brake automatically.

Can you confirm your car is actually detecting the car in front using this screen?

veeeight · Sep 2, 2015

This is correct.

It does not detect stationary traffic.

mls · Sep 2, 2015

veeeight said:
This is correct.

It does not detect stationary traffic.

Really V8 ? it does not detect stationary traffic ?

veeeight · Sep 2, 2015

Yes, correct. It does not detect stationary traffic!

More:
http://www.audi-sport.net/xf/thread...op-nearly-hits-car.206332/page-3#post-2329030

Also on page 117 of the owners manual.

mls · Sep 2, 2015

Thank you ! As always this forum is so informative.

NATOuk · Sep 2, 2015

Just checked in the manual and you're quite right @veeeight - only objects that have been previously detected as moving will be tracked.

Snibo · Sep 2, 2015

Hmmm.....think I might get my old dashcam out of the cupboard and put it on the rear window after reading this Thread.
Don't fancy being rear-ended by some Audi Driver who thinks their car is going to brake - and doesn't.

Forbzeeee · Sep 2, 2015

I also read this in the manual and was going to test it with a cardboard (somehow) but now I don't need to. Cheers

glospete · Sep 2, 2015

NATOuk said:
Just checked in the manual and you're quite right @veeeight - only objects that have been previously detected as moving will be tracked.

But I believe that if you are doing less than 18mph then it will detect a stationary vehicle - which I think is part of the City Emergency Braking. This operates whether you have ACC switched on or not. If the driver does not brake and a collision is imminent then the system applies them automatically.

cemerson · Sep 2, 2015

This is in the manual, and is by design. You wouldn't want traffic bollards or roadworks signs in the road causing your car to stop just before them. Though as glospete says above, if it gets really close it'll automatically apply the brakes eventually with the emergency stop feature.

I'm surprised at the number of people who don't read the manual. There's a lot of information in there, some that is useful to know, some that you really should know before using certain features!

Ignition1 · Sep 3, 2015

Wow - in a way I'm glad I didn't get ACC as that's exactly what I would've done.

I can imagine a scenario where it's tracking the car in front, so when it stops I'll stop etc. I get used to that.

Then that car turns away and I'm approaching a stationary car at the next set of traffic lights...and it doesn't stop.

Yikes. I'll stick to my own ACC (my right foot).

NATOuk · Sep 3, 2015

ACC is pretty awesome in all honesty, it's not perfect (what is) but it works very well as long as you know its limitations.

domino_z · Sep 3, 2015

Must work differently for you guys, but my system works fine in stop start traffic where I approach stopped cars

It does brake more abruptly than you would, but you can tweak that by adjusting the distance gap on the stalk

I'll grab a vid next time in traffic

veeeight · Sep 3, 2015

It will stop for a stationary car ahead, if it had been tracking it previously on ACC.

It won't detect a stationary car ahead, if it hadn't already been tracking it previously

eg you drive in an empty lane, then happen upon a stationary car ahead.

cemerson · Sep 3, 2015

Ignition1 said:
Wow - in a way I'm glad I didn't get ACC as that's exactly what I would've done.

I can imagine a scenario where it's tracking the car in front, so when it stops I'll stop etc. I get used to that.

Then that car turns away and I'm approaching a stationary car at the next set of traffic lights...and it doesn't stop.

Yikes. I'll stick to my own ACC (my right foot).

If you think ACC is a tool that lets you pay less attention to the road, then you will run into trouble, and frankly probably shouldn't have a licence anyway.

gamegenie · Sep 3, 2015

Kind of like how Active Lane Assist, will disable itself if it detects that you aren't steering the wheel.

Well what if you fall asleep at the wheel, or get caught up in a 187 at the wheel, the Active Lane Assist will just say sorry about your luck and steer you right off the interstate/highway.

domino_z · Sep 6, 2015

veeeight said:
It will stop for a stationary car ahead, if it had been tracking it previously on ACC.

It won't detect a stationary car ahead, if it hadn't already been tracking it previously

eg you drive in an empty lane, then happen upon a stationary car ahead.

nope, been testing this over last few days

i set the cruise with nobody in front of me and i get the green radar icon with car below it

as i approach a stationary car at the lights/intersection the icon adds the green car above the radar and the car slows down rapidly

i've tried it up to 70 km/h and i use the default setting for distance - not willing to test it at freeway speeds

checked my only owners manua andl it reads "may be restricted upon stationary car"

veeeight · Sep 6, 2015

What country are you in?
Have you got any other Driver Assist options?

Ignition1 · Sep 7, 2015

cemerson said:
If you think ACC is a tool that lets you pay less attention to the road, then you will run into trouble, and frankly probably shouldn't have a licence anyway.

ACC certainly gives the impression that it's designed to reduce driver input in managing speed - i.e. stopping if the car in front stops. Prior to this thread I would've assumed it would stop if it detected any stationary car - pre-tracked or not.

Primolak · Sep 8, 2015

domino_z said:
nope, been testing this over last few days

i set the cruise with nobody in front of me and i get the green radar icon with car below it

as i approach a stationary car at the lights/intersection the icon adds the green car above the radar and the car slows down rapidly

i've tried it up to 70 km/h and i use the default setting for distance - not willing to test it at freeway speeds

checked my only owners manua andl it reads "may be restricted upon stationary car"

Pretty sure this is what I am seeing as well. I'm in the U.S.

ACC when approaching stationary traffic - oops !

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